I do belive that Zipp wheels are excellent , and one of the best if not the best nut thios data are inconsistent and show the marketing manage that try to raise the bar of his numbers

The problem is that bearings don't experience yaw angles. A bearing is always, always, always going to save 1 watt.

Wheels, on the other hand, DO see yaw angle. So the time savings shown are a reflection of normalizing with some metric over a range of yaw angles. The 1080 is going to be much faster than the 808 at higher yaw angles, and not much faster at all at lower yaw angles.

And it is industry standard to test wheels in a standalone environment, because it is much more repeatable. So testing a wheel solo gives a much cleaner picture. It often does give different numbers than testing wheels on a bike, but then again, you can't test every wheel, on every bike, with every rider.

You are attacking Zipp for being open and honest that not all wind tunnel sessions say the same thing because not every windtunnel session uses the same protocol (wheel only, wheel + bike, wheel + bike + rider).

Zipp is not trying to pull the wool over anyone's eyes. It's not their math that doesn't add up. It's your understanding of how windtunnel tests are conducted.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Rappstar- first- maybe disclose that you are sponsored by zipp....? then... check out the following.

okay- just look at the pdf... the rider data- and tell me what the seconds per watts, equal?

14->16 W = 2 W = 6 sec = 3 sec / watt
16->20 W = 4 W = 14 sec = 3.5 sec/wat
20->21 W = 1 W = 2 seconds = 2 Sec/Watt <---- maybe about right
21->24 W = 3 W = 8 sec = 2.66 sec/watt
24 ->26 W = 2 W = 8 sec = 4 sec/watt
26 ->27W = 1 W = 2 sec = 2 sec/watt
27->30 W = 3 W = 8 sec = 2.66 sec/watt
30 ->33 W = 3 W = 8 sec = 2.66 sec/watt
33 -> 35 W = 2 W = 10 sec = 5 sec/ watt <---- hyper inflated

The PDF makes no sense, since the seconds per watts are not uniform.
Unless I'm missing something -- I'm not saying zipp is wrong -- just that
the PDF lacks much explanation and seemingly makes no sense.

Even in their data- on the rider they mention this:

Quote:

Zipp Tangente Tires can save an additional 3-9 seconds or 1-3 watts).

So- zipp feels their non bearing data should also be falling in line with their max high side of 3 seconds/watt. hmmm and you were saying somthing about the above bearing data not equal to aero data and watts saved ?not? equalling the same time seconds? The numbers in the chart have increases completely inconsistent- as low as 2 seconds/watt (20->21 W = 1 W = 2 seconds = 2 Sec/Watt )... to the grandaddy of them all- (33 -> 35 W = 2 W = 10 sec = 5 sec/ watt ) so please explain why a watt can't be equal to seconds again??? We're talking about Power.

I'm not going to even get into test protocal- where they say the rider "averaged" 300 watts... probably using a watt measuring system that's +/- 1.5-2%... or that using humans on bikes to test wheels- even the slightest movement will change drag data... (that's why cervelo built a zabriskie model to test their frames and equipment- b/c humans are NOT always consistent- a tilt on the saddle, a head movement, anything moving differently) etc. It's nice to see real world data- but it should be taken with a grain of sand... especially the way it's presented.

http://www.trigearreview.com/...ticle.aspx?REVID=523

It says that in his signature, no? Seems like disclosure to me.

---

----------------------------------
Justin in Austin, get it? :)

Cool races:
- Redman
- Desoto American Triple T

std aero ROT: 0.1 lbf drag (measured @30mph) ~=5W ~= 0.005 CdA ~=0.5 sec/km at TT speed

So 1W is about 0.1sec per km or 4 seconds over 40km ... unless you're riding very quickly or fairly slowly.

As I check I ran a baseline static speed/power case with 0.25 CdA, rho=1.2, m=80kg, Crr=0.004. At mid-range TT speed of 12.5 m/s (45 kph) the baseline power is 332.2W and the time 53:20. Note this neglects getting up to speed, hills, wind, turnarounds. Add 1 single W of power to 333.2 W and the time drops to 53:16 for a savings of 4-seconds -> exactly what the ROT suggests.

Re what Zipp has presented, have you considered the effects of simple rounding of power and time to the nearest integer?

If your data is 4 seconds/watt- that is 33% higher than what zipp's research shows... so if YOUR data is correct- Zipp grossly underreported the benefits of purchasing their premium wheels. Why would any company do this? Unless... your data/assumptions are not 100% correct. Zipp's data- for example- on their tires- are a 3 fold range of 1-3 watts saved- that's a huge difference- and what's the margin of error on that testing... 1-2 watts ;)

I stand my calcs for the conditions I assumed. Please note the equations are NOT linear and the ROT only applies for small changes.

I honestly do not know what model Zipp are using. I assume they used FC's actual CdA and mass + bike with some assumptions about Crr and ... possibly wind.

They state the drag was measured at beta=10 degrees but I'm not sure what they incorporated into a model to calculate time savings per w. Was the 300W referenced for FC the model power or simply what he was turrning over at the LSWT erg?

Personally I'd rather just see bloody drag in lbf or gf @30mph and then anyone can simply translate that into conditions and power levels/speed time appropriate to themselves!

The power saved doesn't scale linearly with time saving.

Remember the energy related to velocity³ equation? It's something like going from 9 to 12m/s requires a doubling of power.

Disclose that I'm sponsored by Zipp? You mean the fact that it is listed in my signature line is not adequate?

I wasn't at the testing, so my answer is not necessarily right.

But a couple things to note:

First, something I missed last night, the 1080 is 8 seconds faster than the 808 when used in the rear configuration. The margin of difference is larger when you compare front wheels, as the frame has no interference. So 16 seconds is probably closer to that, which most closely mimics wheel-only testing (wheels are usually tested in a fork). So, perhaps Zipp should list the margin between all wheels in front and rear configuration, but that gets to be a bit confusing.

What you also don't see in that chart is the weighting metrics used for various yaw angles NOR do you see error bars. The wattage savings is obviously some sort of average over a range of yaws. They also base the data on a set of multiple runs with each wheels. There is going to be some rounding. There is going to be some margin of error. A lot of it has to do with the savings at various yaw angles. With these deeper wheels, you have a much larger savings at some of the higher yaw angles. I believe this is the case with the 1080, which actually outperforms a disc at many yaw angles, but then at the much higher yaw angles, underperforms against a disc once the spokes start to see a lot of air.

So maybe Zipp should include error bars, total number of runs done, mean variance, the weighting schema they used, and any rounding they did in their brochure. But that would make it a windtunnel whitepaper, not a marketing pamphlet. The data is presented in such a way to be comprehensible to a lot of people.

I also never said bearing data in terms of watts-secs didn't match up with aero data. I said bearings do not see any yaw. The savings of better bearings at 5deg of yaw is the same as at 15deg of yaw. THAT is what you don't see with wheels. The savings of a 1080 vs an 808 at 5deg is not the same as it is at 15deg.

And, why does Zipp underreport if rmur is correct at 4sec/watt? Because people have hard time with 3 sec/watt, so I'd underreport too. They are being more conservative in their estimates, which I actually know is a fact, because people have a hard time grasping the savings they do report. So they round down to be safer.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

What, you don't trust me? I'm hurt! ;-)

Wow, this is definitely not how I envisioned the discussion on this going down. To start with, the rounding errors in the method Mark is using to compare the data is what are hyperinflated. By comparing the delta time between runs, you are dividing relatively small numbers and getting relatively misleading delta watts. This is the type of thing that companies can (and do) do to make their products look good if they choose...but you see what we have actually done is use the rule of thumb that 1w=3s, and divided the total time savings (which itself was calculated directly from tunnel measured CdA) by 3. Using that method our chart breaks down like this:

42s/3=14w (claimed 14w)
48s/3=16w (claimed 16w)
62/3=20.66w (claimed 20w)
64s/3=21.33w (claimed 21w)
72s/3=24w (claimed 24w)
80s/3=26.66w (claimed 26w)
82s/3=27.33w (claimed 27w)
90s/3=30w (claimed 30w)
98s/3=32.66 (claimed 33)
108/3=36w (claimed 35)


So in every instance except 1, we have actually rounded down, and in the one we rounded up, it was up by 0.33 watts...and I'm not mentioning that we also rounded the time savings in second down as well. This is an excellent lesson for all of us in how easy is can be to manipulate a data set simply by the way you choose to analyse the data.

On top of that, we using a very low rule in saying that 1w=3s. Anybody can go to analytic cycling can run numbers and see that 1w is generally going to equate to 3.5=4.5 seconds for most any condition...but we choose a low number to avoid looking as if we are trying to inflate the numbers upward, and we have been asked by Fabian and CSC not to use the actual number we use in our computer models for Fabian, as that piece of data combined with this info could allow somebody to back-calculate Fabian's CdA...which as you can imagine is a bit of a secret.

As for the arguments about the rider wattage influence on the data. we use 300 watts rider output for athletes in the tunnel as that is an output that is high enough to make the rider sit on the bike and pedal in a way similar to what is realistic, but low enough that he can repeat it numerous times without fatiguing, which generally leads to position changes over the course of a test like this...if we made him pedal at his full TT output, we would definitely struggle with repeatability toward the end of the data set...remember, this sort of data set takes hours to create! So ultimately the 300w and the power meter used has no influence on the data, as the time savings is calculated directly from CdA comparisons using a formula long relied upon by pretty much everybody who does this sort of testing daing all the way back to Chet Kyle and Jim Martin. As for data quality, these CdA values are calculated from average CdA taken for a 1 minute interval at 100hz, so each data point is the average of 6000 measurements, and each point much also satisfy a std deviation criteria for those 6000 points, such that the data point is thrown out and recreated if there appears to be drift or abnormally high deviations within the set (fabian is amazingly stable and we only had to recreate 1 point)

Lastly, in correlating stand alone wheel testing to in bike testing, we have always maintained a reduction coefficient on rear wheel efficiency..and acknowledge that there is also a coefficient for the front wheel depending on fork. This coefficient currently exists in analytic cycling, and is also a rule of thumb value for drag reduction on the rear wheel caused by frame and rider. This number is different for every frame and is also different for wheel in frame only vs wheel in frame with rider as the rider adds additional shielding to the rear wheel. So the argument about the 808-1080 rear wheel being worth 8 seconds in the chart vs 16 seconds in the wheel only data is pretty much exactly as one would expect, with the 16 seconds being spot on for a front wheel and the 8 seconds being about right for a rear in this situation, which was rider on bike at 10 degrees...for this bike w/rider at that angle a 50% reduction coefficient is pretty accurate...note that in the last 2 data points the 1080 front vs 808 front is worth 14 seconds...which is pretty darn accurate to the wheel only data considering all of the added complexity in the system.

Look we certainly aren't claiming to be perfect or to have perfect methods or perfect data, but like any sort of testing, there are always tradeoffs. We will never stop wheel only testing as it is the best way to determine small variations between prototypes, as well as it allows us to look at things more than just drag, mainly side force, stability, and stall performance, all things that are lost in more complex systems. We have even been talking with the LSWT about ways to improve the balance system so we can get individual component drags from more complicated systems...this is currently done using stings at the ARC wind tunnel about 3 miles from our offices here in Indy (too small and fast for bikes)...and could be very interesting for cycling...but at this point is very cost prohibited and still won't solve the question of rider or no rider for product testing. But like anything esle, nothing will be perfect, just like the cervelo tunnel dummy gives high repeatability, but can't offer real world flow conditions on the rear half of the bike due to being static (a condition we also experienced when we used a dummy during development of the zipp 2001 in the early 1990's), our system of doing wheel only, wheel in fork, wheel in bike and wheel with rider (a system that nobody else even attempts) still has flaws as it cannot accurately replicate any fork or any bike....but what it can do is tell us the relative trends between designs and concepts, and it can help us build more accurate math models for converting wheel only data into time/wattage data for our athletes...and in the end I don't think anybody does as much to contribute to the available data and discussion on this topic as we do...and hopefully that is worth something to all of you...

---

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

Josh - 2x comments if I may:
1) Why are CdAs quite so secretive? I can see why you don't give CdAs sufficient that we can all work out numerical drag differences between positions, but can you not even give data from an undisclosed previous date so some of us have some numbers to play with?

2) Can you possibly give me an idea of CdA of a pro cyclist. I was using 0.8 as that's what bicycling science said, but most reports I've read said 0.9. Just a generic value for a good position. Please? *puppy dog eyes*

Just because some people slate your data that doesn't make it bad. I purchased your wheels (and thus didn't eat for months) because you publish data. Keep it coming please!

Kyle published data a long time ago that would put Cd (which seems to be what you're really asking about, not CdA) in the 0.65-0.75 range (depending on yaw angle) for someone in the aero position.

Sorry, you're quite right Andrew; I was after Cd.

The problem is that the data you're refering to is from 1989 I think; cycling science, 1st edition, aero bars and helmets (or some such title) and I was after something with modern kit.

Reference values and improvement of aerodynamic drag in professional cyclists (Journal of Sports Sciences, Volume 26, Issue 3 January 2008) and based on the old Kelme team, indicated a Cd of 0.9ish.

AFAIK, you can't practically separate the two (for the bike/rider ensemble) so why worry about Cd in isolation?

thinking about it: I figure Obree probably had the lowest going for the egg or Superman. Something around 0.55 in the Padilla et al Indurain Hour record paper.

Capelli et al got about 0.22 as a CdA for the Obree. Pretty similar to the CdA of a rider in the who-cares-if-I-die descent position (Kyle & Burke 84)

Regarding separation of Cd and A; Cd is very helpful as it tells you a lot about the shape of a body. Cd and A separately are far more helpful.

I haven't had a chance to read that paper yet, but what do you suppose accounts for the difference: UCI rules, the refusal of many European pro roadies to get serious about aero positioning, or the use of sub-optimal TT equipment by the Kelme riders?

hmmm .... I can see that for a 'bluff body' but a bike & rider is such a mess of different shapes, some rotating relative to the airstream, some fixed ... etc. What does overall Cd and overall A tell you that overall CdA does not? just wondering what your application is?

I'd forgotten that Padilla et al. had estimated Indurain's Cd...

see ... you clearly can't be trusted :-) Neither can I, as the paper actually suggests 0.50 for the Egg and 0.55 for the Superman and .... for comparison Merckx at 0.75.

I guess these are all actually at a track-weighted average yaw angle - around five degrees or so.

I'm investigating the praying mantis position and you'd be shocked how many people say something like:
"Well my frontal area dropped by Xm² thus my drag will drop by X newtons as Cd will remain the same"

Basically, I want to know what happens to Cd as the mantis position is adopted!

Hmm. Sounds to me as if the values are underestimated across-the-board.

I think you should bring this topic up for discussion on www.biketechreview.com.

I have!

Sorry for hijacking the thread; back to Zipp are rubbish and they lie and they use actual kitten blood to make their wheels go fast. Or something.

PS. I'm still after a Cd if possible Josh :-)

I meant exactly as you phrased it in the words I quoted (sorry, inside joke: I've been beating the "you can't assume Cd is a constant" drum for years and years).

I did wonder about that but I sort of figured that it had something to do with cults and brainwashing which , coincidentally, is why I never wear headphones when I use this site!

Please excuse me as I step away from the computer screen. I don't want the same lightning that is going to strike you Josh for being inconsistent in your rounding methods (why oh why did you have to round the ONE result up when the other 9 were rounded down?). You KNEW that wasn't going to go over well on this forum.

Oh the humanity! When is this insane attempt to be honest and forthright going to end? [sarcasm off]

:-)

---

Craig Preston - President / Preston Presentations
Saving the world with more professional, powerful, and persuasive presentations - one audience at a time.

well aside from the Obree positions, the range is from 0.60-0.75 or pretty close to what you 1st posted.

Re the Kelmet data, that sounds like a function of how they measured FA -- maybe camera focal length and where they chose to place the reference area in the frame. IIRC, some folks have an interesting POV on whether or not it should be 'virtually attached' to the rider along the focal axis. I mean when considering the impact on FA of sliding back and forth on the saddle :-) :-)

It's been a while ...

Right, but 0.75 for a standard drop bar position? That would imply that the only benefit of aero bars is a reduction in A, which really doesn't make any sense (since you can reduce Cd in the aero position, at least at 0 deg of yaw, by increasing your aspect ratio).

okay - just read a bit. BSA were estimated using the eq. of Dubois et al and FA was estimated at 18% of that for most cases. Moser and Indurain's data were measured at 0.70 and 0.65 respectively.

So many estimates and just a few measurements in that table 2 of Padilla et al ....

say 0.7 and be done with it ;-)

it's always good to have more data- and the more 'real world' it is the better and I even own a bunch of zipp (and HED) stuff. When I see your comment- above- "So the argument about the 808-1080 .....with the 16 seconds being spot on for a front wheel" On your chart- you say 808 ft/1080 rr (saves 80 seconds) vs 1080ft/1080rr (saves 90 seconds). 90 - 80 is a savings of 10 seconds, not the 16 you mention above or on the website talking about the wheel. Am I reading something wrong here? That being said- it's nice to see the trends, and even nicer to see the real world data published. Now I'm sure Zipp probably tested other wheels- b/c you stack rank so many other wheels. Where would some of your competitors stack rank on that chart? Like a HED 3? As you mention- on the wheel area describing the 1080 wheel- which must have included a test of the Trispoke, "This all new ground-breaking torodial rim shape is designed to provide maximum aerodynamic advantage and has proven to be 29 seconds faster than a trispoke over 40 k."

So am I correct to assume that the 29 seconds- is for a wheel only test? And is that one wheel or a pair of wheels? And what were the numbers (assuming you tested the H3) in the Cancellera test?

Also- there's independent testing (not funded by zipp or HED) that said the H3 is more aero than the 808 and another company- at a "brain symposium" recently said the Hed 90 was more aero than the 808 and you made a comment on that ST thread- that the Stinger 90 is sometimes more aero, sometimes less aero... The H3, according to HED's site, is even more aero than the Stinger/JET 90- so... that should make the H3 more aero than the 808- but for this discussion- let's assume they are equal (give Zipp the benefit of the doubt). I just don't get how you guys can advertise the 1080... "as 29 seconds faster than a trispoke over 40 k." When the 1080 is only 8 to 10 seconds faster than (an equal or maybe slower other wheel- the 808 vs. trispoke) in your real world tests???

Put a "~" in front of that value and I'd be on board with it. ;-)

You are right that the chart has the 1080 at 10 sec faster than the 808 for front wheel, not 14...I'm not sure where I got that number. The thing you are not looking at, however is that this piece of data is based on a single yaw angle, 10 degrees. This sort of athlete testing is not financially feasible, nor is it physically feasible for the athlete doing yaw sweeps, so we work off of a single yaw angle...which coincidentally is the same angle used by almost every frame company and bike fitting camp to test frames and athletes, so this is a very standard test.

As for the 808 vs trispoke, I have not seen any independant data showing the 3 spoke to beat the 808 at any likely wind angle, in fact, the tests we have seen show the 404 slightly beating out the trispoke at wind angles less than 18 and the 808 handily beating it at angles less than 20. Tour magazine posted it's testing on these wheels showing the 808 and the Ritchey Carbon (non-dimpled 404 rim) beat the 3 spoke requiring 18.1 and 19.3 respective watts compared to 19.7watts at 50kph...this wattage savings was based on a weighted average of likely wind angles from 0-30 with the primary weighting placed on the 0 degree condition so assuming more than 80% of wind would fall between 0 and 10 degrees..which is the protocol specified by Tour..by this method they predict the 808 to be 8 seconds faster per 40k and the Ritchey to be 2 seconds faster...but they are assuming 50% of angles will be between 0 and 5 degrees which is where most all wheels have very similar drag, and also are conditions which our models show occur with relativley low probability...were they to move their weighting to 5 or 10 degrees the predicted time savings would nearly double using the Tour data charts.

We also use a weighted average in calculating our wheel only test based time savings (we were the first to start suggesting the use of mathmatically weighted averages based on distributions of angle and not just single angle numbers...actually John Cobb has long suggested the weighting of individual data points, and we really put complex math models to it, and also started collecting extensive field data on real world wind at bike level) based around 10-15 degrees being the most likely wind angles so our assumption (based on rider speeds and more than 1000 handheld wind speed data points from real world race situations) predicts 80% of angles occuring between 5 and 15 degrees for pro road TT and 80% being between 10 and 20 degrees for triathlon racing (lower average rider speeds yield higher effective wind angles for the same given crosswind). Since the drag curves are non-linear, you can pick and choose data if you like depending on wind angles, we could have picked 12.5 for the cancellara test, which is the angle of peak minimum drag of the 808 or 14 degrees which is the peak minimum drag of the 1080 and made the numbers look even more in our favor for this test, just as we could do the same for wheel only testing, but as it stands, we run our formulas for our published wheel time savings based on a statistically weighted average of the drag curve and not a single point. Since large data sweeps weren't possible using Fabian, we stuck with the accepted standard test protocol, and we describe that completely in this test. For the wheel time savings claims we describe that protocol as well, and we have been instrumental in creating the use of the weighted probability analysis of wind angle, which is now heavily used in the pro-cycling ranks to make equipment decisions and to predict TT times....not just for our athletes but for competitors as well, which is why we keep Cd and CdA data such a secret.

As for the 808 vs stinger 90, we have talked on this very site about us beating the 90 with 21mm and narrower tires and them slightly edging us with 23mm and larger tires...we even posted this graph last year showing all of the wheels in question showing the stinger90 to be quite fast...of course is was more than a year after the 808, has ~11% higher side force in a crosswind and is ~1lb heavier, and a few hundred$ cheaper, so how you weight that is up to you. The 808 is 4-5 grams better on average with 21mm and the stinger is 4-5 grams better average with 23mm from our numbers, though of those 4 runs the 808/21mm tire has the lowest overall drag. You can also search this site and find other wheel only testing we have published, including an analysis done by Dan I believe showing our numbers for the Hed3 matching almost identically Hed's numbers for this wheel. There is also some Tour magazine graphs posted which show them getting even better numbers for the 808 than we show here. I am not sure why Hed pushes the H3 over the stinger90, when by our testing the 90 is without a doubt the faster wheel in almost every condition so I can't speak for them, but by our thinking (as well as that of the guys at the wind tunnel and most anybody else, the 90 is the faster wheel of the 2)




Since the 1080 extends the sweet spot of the curve out to 14 degrees, this makes the 1080 a good bit faster using the weighted average of yaw as the 1080 holds it's peak minimum drag over such a wider range of yaw angles. Again, had we run the cancellara test at 14 degrees, we probably could have 'proven' the 1080 was 30+ seconds faster than the 808 and 45 seconds or more faster than the 3 spoke. Actually by chossing the industry standard 10 degree yaw for the cancellara test, we were in effect further reducing our own advantage...particularly when we focus more than 80% of our design time studying the area between 10 and 20 degrees of yaw with about 65% of that time and money spent looking at 10-15 degrees...hence our strengh in those areas. So having said all that, 29sec is a conservative number for advantage of a 1080 pair over a 3 spoke pair using a weighted wind angle average centered around 15 degrees.

In the end, anybody here can say whatever they want. I feel that we go out of our way to be honest with our testing, realistic with our numbers and we generally try to be conservative with our claims. We always divulge the protocol of the test (something I never see in any other data) and we publish more data and graphs than all other companies in this industry combined when it comes to aero. We also spend more time and money doing what I would consider basic science type testing specifically for informing the public, such as our extensive wheelset comparison test at 20mph, 25, and 30mph to debunk the popular myth that 'aero only works at high speeds like 30mph' and our publication of white papers on our website being the first to really discuss designing the rim to match the tire and choosing the tire to match the rim, as well as other studies like our direct comparison of identical wheels built with various spoke counts, aero comparison of spoke shapes, the first aero studies on tires and so on. So say what you like, but nobody contributes as much to this discussion as we do, nobody divulges as much info as we do, and nobody takes as much crap for contributing as we do...in the end, my theory is that there is no reason to inflate this data now that anybody can go to the tunnel and disprove it...certainly we can be made to look bad at a certain angle or with a certain tire or whatever, but we will not lie about this...it's just too easy to be disproven...

---

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

thanks for posting that Josh. Personally I'd have been quite happy with lbf or gf drag reduction @30mph tunnel speed and stated beta but I had no issue with the data as presented.

Not meaning to go off on a total tangent but did you see this thread and linked Rolf LSWT data from ~3wks ago? Any comment on the low yaw angle performance of the low-spoke count wheels (and tire combo)?


http://forum.slowtwitch.com/...t_reply;so=ASC;mh=25;

Ditto!!!

Uhmm.. instead of worrying about 1 to 2 Watts, why not just train a little more and pedal a little harder? Seems to be the cheaper alternative to me.

-- Boris

Since when are such things mutually exclusive?

Josh: It would be really interesting to see a vector plotting of wind effect/yaw for a rider at intervals during a typical course.

Do you have much, if any, real-world data (I am sure you do) on what a typical rider actually experiences over the course of an event? Just a very simple observation, such as the vast majority of courses are closed loops, and seeing how wind and yaw change and effect would be interesting.

It would seem that 10 degrees means that wind is assumed to be a net negative factor in a ride?

Not if you're using the right equipment.

Hmmm...I may have...but I can neither confirm nor deny if it exists due to a non-disclosure agreement ;-)

However, if one were to search on "808 vs. trispoke" one may find some "independent" data appropriate to this subject. It also may cost a few ducats to find out which one tested better.

To be fair though, the testing was done with a Conti 20c tire. It's well known that the trispokes perform better with a much narrower tire. Now, what the Crr "hit" would be running that narrow of a tire is a whole 'nuther subject ;-)

---

http://bikeblather.blogspot.com/

Depends on the brand, no?

Low aero drag, low Crr, high puncture resistance: pick two of the three. :-)

Everytime I read your posts I feel like I learn something and it makes me happy that I have your wheels.

what is the Crr hit with a veloflex record 20 tire ;)

It may be a "plus" depending on whatever tire was used before...then again, a VF Record 20 clincher measures more like 21-21.5 when mounted, so it won't be as good aerodynamically on a trispoke like a true 20C or 19C tire.

You also may want to consider the negative aero effects of the "lip" on a glued-on tread type tire (like the VF) vs. the smooth surface of a "vulcanized in one piece" tire like a Conti or a Michelin. Josh may be able to add some enlightenment on that with their experiences with the Vittoria tires.

Any wonder why I try not to put many miles on my last remaining Michelin ProLight 20C tire ;-)

---

http://bikeblather.blogspot.com/

Or...go with the low aero drag and low Crr, but then fill the tube "prophylactically" with some latex sealant :-)

---

http://bikeblather.blogspot.com/

Okay- thanks for the added information- more information is always better- if it's accurate- than it's even better. Let's take a look at the above chart. I can't comment on zipp's zipp wheel data- but you can compare Zipp's HED data to HED's website. Zipps numbers re: the 60, 90 and H3 are not even remotely close to HED's numbers for their wheels (If you're paying for the tunnel time- you better get the numbers to land on the right side up!) anyway, the H3 drag on Hed's site- is 161 grams and 158 grams at 15 and 20 degrees yaw, respectively. Zipp's graph appears to be at 200 grams at 15 degrees(an increase of 24% of drag over HED's numbers for the same wheel- which makes it go from wheel number 1 to wheel number 5 at that point in the stack rank) and at 20 degrees yaw- it looks to be at 172 grams- which is the best in the stack rank- but in reality HED had it at 158 grams or 9% faster than what the chart shows... So it would be even better. And the graph is way high from 0 to 10- where HED has the wheel below 200 grams (190 grams at 0 and 192 grams at 5 and 180 grams at 10 degrees yaw)- but Zipp has the same wheel well north of 200 grams- again inflating the drag of HEDs wheels by 10-15%. Again- independent data (Cervelo) said the Stinger 90 (which is actually slower than the JET 90) is faster than the 808 (p.s. Tour didn't test the 90 or 1080- that's a shame)- but of course the data above- has the 808 faster at every single point- or at least equal. Sounds like someone (who's huge in the industry- Cervelo) called you out on the carpet on this one " but we will not lie about this...it's just too easy to be disproven..."

Also- Zipp talks about the virtues of their Tangente tire being 1-3 watts faster- which is 9 to 27 grams of drag better- than the next best comparable tire... So- why wouldn't they want 9 to 27 grams of less resistance by using their superior aerodynamic product on their own product- to give them even better numbers when they are tested? You didn't use that tire on the above charts or the recently posted Cancellara data... Why not??? Isn't it all about "The True Aero Edge"??? Ironically- their 2 ~60 mm rims (404 is actually 58 mm)- vary greatly- and the one that is much slower- in fact the slowest wheel of all the Zipp's listed above- is the one with the far 'superior tire'....

... as a personal fyi- I have owned/purchased all of the following wheels in my past- Zipp- 808, dimpled disc, non-dimpled disc, 404, 440, 303, cages, skewers, Vuka swift shift. And HED- disc, freewheel disc, JET 60, 90, clip-on bar, full aero-bar, H3... so both of the above companies have at one point or another received a lot of coin...

I think this may be some of the data to which you are referring:



When you plot it out, it appears to me that the primary difference is simply the point at which the 808 effectively "stalls". Specifically, the CSC (? I always assumed it was some other team) -generated data says that this happens around 10 deg of yaw, whereas the Zipp data indicate that it doesn't happen until around 15 deg of yaw. It seems to me that said difference could easily be explained by small differences in, e.g., the test protocol, the type of tire used (width wouldn't seem to explain it, at least based on the CSC data), etc. I suppose you could argue that Zipp has manipulated such things in their favor, but doesn't it really make more sense to think that it is the other way around, i.e., their design may have been driven in part by the test protocol that they use? After all, even the CSC data shows that both the 404 and 808 "sail" to some degree; it's just a matter of how far out such an effect remains.

(BTW, a similar difference exists in the 404 data, whereas the the Zipp-generated Specialized Ultralight vs. CSC-generated HED3 datasets are practically superimposable, as are the corresponding disk datasets.)

surely that would kill the Crr.

Not according to AFM's roller testing. No detectable difference in Crr.

---

http://bikeblather.blogspot.com/

Why so angry Mark? Josh and others effectively shot down your first hyperventilating post. And yet you persist with the sputtering and the moaning. And the jumping to conclusions. And the thinly veiled accusations of data cooking.

I'm amazed that the other posters in this thread have the patience to respond to you at all, much less in the balanced, detailed, and thoughtful way that they have.

Still, lots of interesting data presented here. So carry on I guess...

Rik

regarding the difference between the FP60 drag and the 404 tubular drag, i suspect most of it is due to the fact that the FP60 is a 20H crossed lacing (1x?) wheel while the 404 is 18H radially laced. That has a much bigger impact on drag than tire profile.

As for why they did not use a tangente tub on the other zipp wheels for the cancellara data, i speculate that it is because that testing was first and foremost for the benefit of Cancellara and not the general public. Cancellara has to use vittoria evo cx because that's what the team uses so it does not make sense to test with anything else.

not angry at all- just fact finding.... so here's some more interesting data.... of the below chart that Josh posted- notice that the FP 60 wheel- performs much better than the H3- until 10 degrees of yaw... and then the H3 out performs the FP60 from 10 degrees onward of yaw- very easy to see- at least with Zipp's data. On the VERY next chart that is posted (also at 30mph)- which is found on Zipp's flashpoint site (so, again Zipp's own data)- they have the same FP 60 wheel- not only out performing H3 at 0 yaw, 5, yaw, but much better at 10 yaw, 15 yaw, 20 yaw, AND then finally the H3 is more aerodynamic at 23/24 degrees of yaw.... (basically the chart is saying FP 60 is the better wheel for 95% of all riding conditions... hmmm) Same company- same wheels- being wind tunnel tested... but wow- whatever wheel they are selling- it seems to magically get better... not angry at all- just fact finding! As Josh says- "but we will not lie about this...it's just too easy to be disproven..." I guess their own charts question or answer the preceding statement.



The below chart is hard to read- but the direct link is here and easier to read: http://www.flash-pointracing.com/technology/aerodynamics All you have to do is compare the blue triangle to the vibrant green on the above chart. On the chart below-track the lowest line- light blue to the tannish line with the orange square.... (more or less the bottom (best) two lines)
Aerodynamics - The Shape of Speed
Flash-Point wheels are born from the lessons learned while winning grand tours, world time trial championships and Ironman World Championships. And that speed is all yours to enjoy on each and every ride.

OK, not angry. It came across that way to me.

The chart from the Flashpoint chart indeed does not seem to align with what we "know" about the HED3 - decreasing drag at large yaw angles. It does seem to match the data shown in this chart: http://www.zipp.com/.../Images/diagram3.jpg which appears to have data mostly from 2004. Different testing protocol perhaps?

If Josh is still watching this thread, I'd be interested also in any data for the Flashpoint 80 wheel (front). It would be interesting to see that against the data for the 808 and see the difference that the dimples (and lower spoke count?) make.

Rik

Keep in mind there are a couple of iterations of the FP60 though. I wouldn't be surprised if the newest one performs better--and better than the 404...

In a certain sense, I agree with your general point. Zipp (and all companies) are selective in what they publish. I don't believe they're making stuff up, but I do think they're going to publish things in a way that makes them look the best. As a consumer, it kinda makes sense to take that into account when looking at the data.

I also think they have to balance publishing yaw sweep charts at grams of drag--that only a few people will really understand or care about--versus a quick '30 seconds over 40K' sorta thing, which is what most people really want to know.

When pressed on details, they've always been pretty forthcoming about the test protocol, so I think you have to give them credit in that regard.

And how do we know that they don't act as tripwires? Has anybody compared the exact same tire casing with a glued-on or vulcanized tread, and demonstrated that the former produces more aero drag? Failing that, has anyone done any CFD of the problem?

All very good questions...and I guess I left out the word "possibly" before "negative" above. I based my speculation on some info told me by various Zipp folks trying to explain why some of their wheel plots don't match earlier plots as well as they should (especially in the "magic" 5-15 deg. yaw range). Apparently, they claim they were able to detect differences in a tread mold used by Vittoria....

---

http://bikeblather.blogspot.com/

Okay...what podium are you gunning for that is going to make your time on the computer doing research going to be better spent than time training?

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

Why is that an "either/or" proposition? Can't he spend time on the computer researching when he's recovering from his training?

To quote John Forrest Tomlinson on rec.bikes "Can I do both? Is it allowed?" :-)

---

http://bikeblather.blogspot.com/

One way to interpret that data is that the lip on the tread of the Vittoria isn't big enough, such that further disrupting the flow via strategically placed dimples provides a benefit.

I don't really think you can compare the actual drag numbers from HED's site with Zipp's. Results are really only valid for a given round of runs in terms of comparison. Air density, for example, would have an impact. And if the tests weren't conducted in the same tunnel, that could also impact the numbers. HED also doesn't state the speed the tests were run at. Given the enormous difference, my actual guess is that those numbers are for 25mph, not 30mph. I actually think that all of the data on HED's site is for 25mph. I seem to recall (though I could be mistaken) that they report for 25mph.

In any case, the large difference between Zipp's values for HED's wheels and HED's values is not suspicious at all. Unless you can confirm that the tunnel conditions (air density, etc.) were the same, speeds were the same, and tunnel were the same, any (or all) of those things could be reasons.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

And this coming from someone who has posted 14,159 times on Slowtwitch or 7.3 per day for the last 5-6 years?! ;)

Rik

I guess ultimately we are all going to see what we want to see here, and we have released so much data over the years that you can always go back and nitpick it however you would like. In the end, I welcome any of you to go and create your own data sets and post them for free on this website. You could easily replicate the cancellara test for about $10k plus the cost of the product, travel, lost time, etc...and most of the other data sets for $3-4k each...but remember, that every time you want to try a different tire, or change air pressure, look at additional yaw angles, etc... you are effectively doubling and then tripling the cost and time involved to test

As for the FP data vs. teh other data set, you are talking about two totally different wheels, tested at 2 totally different tunnels (Texas A&M and one at SanDiego), plus different tires, and ultimately the A&M set (the one of hte fp site) uses the A&M tunnel protocol of yawing from 0 to 30, which we do in reverse as a 30 to 0 sweep as yawing the wheel in both directions yields a rather large hysteresis. The 30-0 gives you the worse of the 2 graphs (but the more repeatable one) and more importantly shows the ability of the wheel to perform after stall has been acheived, rather than starting with perfect flow conditions and seeing how long you can get the air to hold on...we feel this is more representative of real performance as real air is actually rather turbulent. However, the biggest issue here is that the FP data set on the FP site is was the prototype wheel for the NEW FP60 which uses 8 fewer spokes and an updated rim shape, while the other data set was taken using what was then the current production FP60...so other than it being a different product at a different tunnel using a different protocol, we are most certainly a bunch of manipulative and lying bastards.

As for our data matching or not matching the Hed data, I can say that their data for the H3 does not match any we have ever created for that wheel with a 22mm tire, and looks more like that wheel with a true 19 or 20mm tire (tires measuring out larger than 20 really start to degrade the performance of that wheel). Our data for the H3 and the 808 matches within a few % of the Tour magazine data which was conducted with 22mm Continental tires. They even replicated exactly our claimed stall angle of the 808 at 12.5 degrees and discuss this in the 2005 wind tunnel test. They retested the 808 in 2007 using smaller yaw increments and matched it again...and again actually posted even lower numbers for the 808 than we have ever published. In reality, it is the Hed data that cannot be replicated for the tire in question, as that data much more resembles the pay per view data which was using a 20mm tire (which truly measures 20mm or less) and at an unrealistically low pressure, and seeing as tire pressure increases tire width and alters tire shape, this is very, very important.

As for the cervelo test, they were using a wider tire in that test and the results were almost exactly as we had discussed in our dicussion on ST about the stinger90 over a year ago, so I'm failing to see what is new here. The fact that the wheels are within a watt or two of each other with that tire says alot for the relavance of the 808 seeing as the 808 concept predates the stinger by almost 2 years, and was designed for 21-22mm tire and not 23 as tested. Not to mention that the 808 has 11% less side force in a cross wind for more controllable handling, and is lighter...but thinking of those things may lead us to have a more nuanced discussion on wheel choice...which is clearly NOT what this discussion is about.

---

http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

Out of curiousity, (how) do the dimples on the Zipp tire impact this? I ask because I was just reading about how a properly sized/positioned tripwire not only reduces overall drag (of, of all things, a bob on a pendulum clock!), it also minimizes such hysteresis.

Hey, I am not trying to slice aero hairs and try to make a Tri company look like they are up to no good. I admit I have nothing better to do with my time....but in my spare time I am not trying to find a conspiracy.

---

----------------------------------------------------------

What if the Hokey Pokey is what it is all about?

Yes.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

I see that I have taught you well, grasshopper. Now that you have snatched the pebble from my hand, it is time for you to be the master and I the student.

Hey Damon,
How about combining the Bontrager Aero tire design (in particular the "wings" at the bead interface) with the Race X-Lite Pro casing? ;-)

If there's one thing I always shake my head at is the fact that the Bonty Aero tire uses such a low TPI casing...

---

http://bikeblather.blogspot.com/

LOL! Thanks for playing the straight man. ;-)

Have you seen the Bontrager TT tire? Rolling resistance isn't stellar, but even taking that into account, with the aero advantage it's still faster overall than 6 other tires we tested recently at LSWT.com, among them one with dimples.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Hmmm...so, are you saying that the aero advantage is enough to counteract it having worse Crr than a Tufo Race Lite? Or, are you just talking about it being faster aerodynamically?

Let's see, if we compare it to a 23C Vittoria Open Corsa CX, it's drag is lower by at least 5-7W per tire??

Numbers, please ;-)

---

http://bikeblather.blogspot.com/

One way to compare wheels and tires is to compare total (wheel+tire) drag, where
Total drag = Rolling drag + aero drag.
This is just for the wheel and tire combos, and assumes all the other drag is unaffected (frame, rider, clothing, etc.), so I'm just comparing wheel and tire choice here.

1. Rolling drag can be calculated from AFM's data, and I threw in a 1.5 fudge factor to bump up the rolling drag so it's probably closer to what it might be on real roads (compared to smooth rollers):
Rolling drag = Crr * weight * 1.5.
I used 100 pounds for the weight since that's about how much weight I put on my front wheel. I know, I could stand to lose a few pounds. ;-)

2. Aero drag is an output from the tunnel. I averaged 5, 10 and 15 degree yaw readings to get a rough estimate of where I race.

Adding rolling and aero drag gives me a number to compare wheels and tires with.

Tire (size) / Tube (size) Total drag, grams
Zipp Dimpled Clincher (21) / Michelin latex tube (18 / 20) 415
Bontrager Race X Lite Pro (21) / Michelin latex tube (18 / 20) 411
Zipp Dimpled Clincher (21) / Michelin latex tube (18 / 20) 407
Bontrager Race X Lite Pro (23) / Michelin latex tube (18 / 20) 388
Bontrager Race X Lite Aero TT (19) / Michelin latex tube (18 / 20) 380

Notes:
1. This list is sorted from slowest at the top down to the fastest at the bottom.
2. It's also interesting that the first three tires listed appear to be identical except for the tread pattern.
3. AFM's Rev 6 doesn't include some of these tires, I sent Al some and he kindly ran the testing. They should appear in Rev 7 when that's ready.
4. All tires were run in the tunnel on the same wheel: Bontrager ACC.

There are probably other ways to slice this data, too: different weight, different fudge factor, etc.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

"4. All tires were run in the tunnel on the same wheel: Bontrager ACC."

How wide is that wheel?

Thanks Damon! Interesting stuff. What's the difference between the first and third entries? They look to be the same description.

Yes, I'm aware that Al's got some newer data...in fact, I sent him some tires too lately ;-) BTW, did you guys ever figure out why that 23C Race X-lite Pro seemed to roll so special? I seem to recall that the casing thickness on that particular tire seemed a bit thinner than expected...

---

http://bikeblather.blogspot.com/

21.5 mm at the rim, and that's it's widest point. Interestingly, we also included a Zipp 404, which measures a little over 18 mm at the brake track and a little over 23 at the bulge, but the tunnel numbers were about the same.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

The first and third entries as far as I know are just representative of the normal variation in Crr from one sample to the next.

About the super fast Bontrager Race X Lite Pro 23 mm tire, Al and I thought it was a fluke, too, but I sent him three more that tested the same, so maybe it's true (fingers crossed)! We did measure thickness, weight, etc. and the first one was exceptionally light but it didn't seem to make a significant difference in Crr.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Interesting. Did you mean variations in CdA, not Crr? I thought you wrote that you took Al's number x 1.5.

BTW, at what speed did you calculate your "total drag" numbers above?

Also, is the pic for the Aero TT tire on the Bontrager website correct? I'm not seeing any "wings" on that thing...

---

http://bikeblather.blogspot.com/

I think Damon is referring to the two entries in Al's (AFM's) Rev. 6 list for "Zipp Dimpled Clincher"? One was for a new tire and the other for a used tire (~ 60 miles).

Rik

Josh: I for one appreciate all of the time you spend here to explain your testing results and data, and walk us through the testing methodology and specifics. You refer to one thing that has bothered me about HED's data on their website regarding the HED3. The drag data for the H3 (aluminum) is listed as with a 22mm tire, but the data for the H3C (carbon) is listed as with a 19mm tire. But the drag numbers are listed as worse for the H3C at 10 degrees and above on HED's website!

Do you have any testing data on the Flashpoint 80? Or barring that, what would your estimate be of how it would stack up against your published data of the 808?

Rik

I agree, the pic isn't the best, but I also think you may be looking in the wrong place...based on the description (and Damon's comment above), the Bontrager tire apparently has a small wing/lip/flare to help ease the transition from the tire casing to the rim (just like some Michelin tires had back in the 1990s). You could therefore take the data he's posted as an endorsement of the idea of using silicone caulk to fill that gap.

Nope...that's where I was looking, i.e. along the bead/rim interface.



I'm still not seeing it...

---

http://bikeblather.blogspot.com/

FWIW, the little 'wing' on the old Michelin tires was pretty small (2-3 mm wide?), such that the tire still curved in before flaring out again to cover the horiztonal portion of the rim/brake track. I *think* I see the same thing in that pic...but it could be that I'm just imagining it because of what I expect it to look like.

I'm not seeing it in that photo either, but here it is on my bike:



Bontrager Aero TT 19 mm tire

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Modolo Kronos front brake?

Close! Weinmann Delta.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

does it brake better than a modolo kronos?

---

=====================================
S�rgio Marques
When it hurts is when it feels good ;-)
Sergio-Marques.com

Much better. I definitely see it there. Thanks.

OK, so what does this "19C" tire really measure? On Al's chart, it looks like he measured it to be actually more like 22mm wide.

Also, in case you missed it above, what speed did you use in your "total drag" calcs you posted?

Thanks again!

---

http://bikeblather.blogspot.com/

"tripwires"

Bad Crr notwithstanding, my old Conti Supersonic 20c's had 3 little "wires" on each shoulder. Tripwire effect would be the only reason I can see to put them there...they also measured a true 20mm (matched up well with my Trispoke), and I had some very fast TTs on them back in 2004 and 2005, before I started looking closer at Crr data and switched to Michelins & Vittorias.

While I don't ride Zipp wheels on my tri rig (although I did just add old 340s to my cross rig!) and am a self admitted skeptical and completely cynical bastard, emphasis on the bastard for sure, I have to say I hope you're able to slough off crap like this from people who know very, very little to nothing about truly testing. It's clear to most (I think) people that you guys test the bejeebers out of your stuff and while I have to say that you clearly don't go out of your way to pick test results that make your product look bad, you do seem to go out of your way to not overly inflate your numbers and to go through some pretty darned extensive testing.

Anyway, all I'm trying to get across is what others have said, while we'll all still be watching your figures, don't worry too much about aberrant misfires who are convinced against all evidence that you are making up numbers and make an inferior product. As the old saying goes, you can please some of the people all of the time or all of the people some of the time, but most of the time some people are jerks. That might not be a direct quote but I'm pretty sure I have it about right.

-Andrew Saar

---

-Andrew Saar
It is better to do the right thing and be paid poorly,
than to do the wrong thing and be rewarded richly.

Ah, I dreamed of owning a Kronos when I was a kid and they were new. But alas I've never ridden a bike equipped with them, so I can't compare , sorry!

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

I meant variations in Crr. Pretty sure Al has two entries for that tire. Though CdA varies too of course. ;-)

Drag data is at 30 mph (no, I'm not that fast over long distances - I race pursuit :-) )[/reply]

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

aaah, i have one as front brake in my trek :P

they...well, slow you down, especially when the replaced brake was a bontrager speed limit witch is amazing

---

=====================================
S�rgio Marques
When it hurts is when it feels good ;-)
Sergio-Marques.com

I measured mine at 20.2 mm mounted on my old Dupont 3-spoke and inflated to 120 psi.

I also just saw Al measured Crr for a new tire; I think he's found Crr drops after a few training rides. Might have to send him a couple of my used ones.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

If I understood our tire guys correctly, this ridge(s) is sometimes designed into tires to "catch" the edge of the tread rubber during molding to prevent a cosmetically wavy edge between tread and sidewall.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Yeah, I was amazed too when I put those on my bike for the first time! Very confidence inspiring for me.

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

I misread the Vernier when I measured the first time adding a bonus 0.100 " to the width. I remounted and remeasured the new tire inflated to 120 psig at 19.4 mm on a Velocity Aerohead Rim. I see tire Crr typically drop ~ 0.00015 after ~ 50 miles or so. The width also goes up possibly due to assuming a more circular cross section due to "road softening" or stretching of the tire or both ??

Al

The 2 entries are for the same tire new and used. I've seen the Crr drop typically ~ 0.00015 after ~ 50 miles possibly due to softening or stretching of the tire ?? The width also typically increases a bit.

Al

Thanks for the info Al!

---

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

[/reply]

Thanks Damon. I think there may be a danger in just giving a "total drag" number at just one speed. This is because the "drag" force related to Crr is constant (or nearly so) and the aero drag force varies with the square of the apparent wind speed. That means that a tire such as the Aero TT, even though it's great aerodynamically, may not perform as well at lower speeds due to the higher constant "offset" due to it's high Crr.

Here, I "reverse engineered" your tire data over a range of speeds from 1 to 35 mph and plotted the results. I was curious as to what the "crossover point" would be for the various tires where the better rolling resistance would win out over the better aerodynamics of the Aero TT tire.



As you can see, on this wheel, both the Zipp dimpled 21C clincher and the Race X lite 21C actually have less total drag below 20-21 mph, while the 23C Race X Lite Pro is faster overall at speeds all the way up to 28 mph.

It's also interesting how the 23C RXL Pro is better than either of the two 21C tires listed all the way up to 35mph, even despite it's somewhat worse aerodynamics. That really says a lot about how valuable a low Crr tire can be.

NOW do you see why I was asking about having the wings put on a casing like the RXL Pro?? ;-)

I'm also thinking I may have to apply a bead of RTV to my VF Record front tire on my TT wheel....:-)

---

http://bikeblather.blogspot.com/

Thanks Damon. I think there may be a danger in just giving a "total drag" number at just one speed. This is because the "drag" force related to Crr is constant (or nearly so) and the aero drag force varies with the square of the apparent wind speed. That means that a tire such as the Aero TT, even though it's great aerodynamically, may not perform as well at lower speeds due to the higher constant "offset" due to it's high Crr.

Here, I "reverse engineered" your tire data over a range of speeds from 1 to 35 mph and plotted the results. I was curious as to what the "crossover point" would be for the various tires where the better rolling resistance would win out over the better aerodynamics of the Aero TT tire.



As you can see, on this wheel, the both the Zipp dimpled 21C clincher and the Race X lite 21C actually have less total drag below 20-21 mph, while the 23C Race X Lite Pro is faster overall at speeds all the way up to 28 mph.

It's also interesting how the 23C RXL Pro is better than either of the two 21C tires listed all the way up to 35mph, even despite it's somewhat worse aerodynamics. That really says a lot about how valuable a low Crr tire can be.

NOW do you see why I was asking about having the wings put on a casing like the RXL Pro?? ;-)

I'm also thinking I may have to apply a bead of RTV to my VF Record front tire on my TT wheel....:-)[/reply]
hi tom,
what mass, rho and percentage of raw roller Crr did you use for the plot? Definitely the very best way to look at it for one's personal case!

just to confuse this even more....

I think it's important for anyone else looking at your (excellent, btw) chart is that the break point will be different based on rider weight and position. For instance, someone like me (a 62kg rider with a very rearward position) is in a different boat than a 200 lb guy riding a 90 degree seat angle.

I used Damon's 100 lb load and 1.5x "road roughness" factor to back out the aero drag at 30 mph. Rather than assuming a rho and solving for CxA, I just scaled the aero drag as the ratio of the apparent wind velocity squared over 30 mph squared (i.e. (Vw^2)/(30^2) )

But, once the "aero drag" is solved for, you can then modify the Crr drag for your particular wheel loading and "road roughness" assumptions and see how that affect things.

---

http://bikeblather.blogspot.com/

okay. For me that'd be ~250 lbs load ;-) which would change the intersection points or possibly remove some.

the 1/2*rho*CdA bit makes sense ...

Just for "giggles", I added 2 more "speculative" entries. The first is for a used VF record and the assumption is that it's aerodynamic performance will be the same as, or very close to, the Zipp and Bonty 21C tires. The second is for the same tire, but if it could somehow have the "wings" of the Aero TT added (with, perhaps, a bead of RTV?) and thus the same aerodynamic performance of the Aero TT tire. Again, this is for the 100 lb tire load case that Damon originally assumed.

It appears that the VF would perform nearly identically to the RXL Pro 23C tire, which isn't surprising since they have nearly identical Crrs and the aero drags appear to be similar as well. The performance of the VF, if it could get the aero drag of the Aero TT tire, is potentially outstanding. At 27mph, you're talking about a potential difference of ~70g of total drag force. That's equivalent to a time gain of ~.75s/km...or, ~30s over a 40K.

Enjoy.

---

http://bikeblather.blogspot.com/

Damon...I keep forgetting to ask, but when is the ACC wheel going to be available? The Bonty site says that they aren't available yet.

Also, is it possible to just buy a front wheel?

---

http://bikeblather.blogspot.com/

no quote this time to cut down on the trailing bits .. can you tell me where the 'wings' would be applied? are we talking the right down at the tire/rim interface gap? or further back up the sidewall?

interesting ideas! I have some old school green Axial Pro's home somewhere in a bag!

thanks! You're a fountain of useful info lately...

This is exactly what I was looking for in an earlier thread re: clincher v. tubie.

Yeah...that's the idea...filling the "gap" at the tire/rim interface right at the bead. Just look at Damon's photo above to see that.

Now...don't forget that the BIG ASSUMPTION is that filling the gap this way will be as effective aerodynamically as the "wings" on the Aero TT tire...AND it won't adversely affect the Crr either. There's some old data here on doing this, but by my figuring the advantage only comes out to be ~5 grams of drag at 30 mph from the value listed in the table under "fill the front tire gap at the rim".

Damon's data implies that it would be more like ~60g at 30 mph. Perhaps the advantage is greater with the deeper, more aerodynamic rim (since the flow is attached further along) than with (what I assume to be) a shallow profile rim with lots of spokes?

---

http://bikeblather.blogspot.com/

Yeah...I should probably "shut up" now...I'm just potentially helping my competitors get faster ;-)

---

http://bikeblather.blogspot.com/

You mention the wheel- was the Bontrager ACC. Is that the 5.0 model or just a regular box carbon rim or?

thanks!

hey Josh, this may have been asked, but........
say i have both the 808 and 1080 front wheels and the option to use either in an upcoming race. since your study is at 10deg yaw, and comparing to Hed's data on their own wheels, wouldn't the 1080 possibly be slower than the 808 at high yaw angles, but faster in low wind? looks like Hed's wheels are admittedly slower at high angles the deeper they are, so wondered if yours were the same trend?

[/quote]

---

i find this a bit strange that you not measure the CRR in the field and as you might know every surface has its own roll coeff and its not allways linear as you calc linear

---

http://www.ada.prorider.org
skype ceesbeers191053

Its funny to see ,that you never see a riders tested with back wind or any equipment testing ,i guess they never do or know anything from this.

And its good to see they they gone use tufts in windtunnel testing as we started that in using that begin of the 90th .
Well they need a dummy first meaby they finaly gone used it also with real riders.
And will take sometime they gone use realtime CFD in the windtunnel i guess will take them 15 years to catch up too.

---

http://www.ada.prorider.org
skype ceesbeers191053

I find it funny to see that the only times you post are to tell people about how they're obviously doing something wrong and that everything you do is years ahead of that...and yet, you never add anything constructive to the dialog.

---

http://bikeblather.blogspot.com/

hmm, the way i recall it they went from non-existant to top of the heap in less than 10 years......eh?

do you need any help patting yourself on the back? Geez ...

http://picasaweb.google.nl/...#5188847982716858626

---

http://www.ada.prorider.org
skype ceesbeers191053

Yep...that's constructive <rolleyes>

---

http://bikeblather.blogspot.com/

http://en.wikipedia.org/...le_image_velocimetry

---

http://www.ada.prorider.org
skype ceesbeers191053

[/reply] hey Josh, this may have been asked, but........
say i have both the 808 and 1080 front wheels and the option to use either in an upcoming race. since your study is at 10deg yaw, and comparing to Hed's data on their own wheels, wouldn't the 1080 possibly be slower than the 808 at high yaw angles, but faster in low wind? looks like Hed's wheels are admittedly slower at high angles the deeper they are, so wondered if yours were the same trend?[/reply]
anyone comment???

I think you should be able to find data that has the data for both at various yaw angles. IIRC, the 1080 continues to do better than the 808 as yaw angles increase. The 1080 actually bests the 900 disc below 12.5deg of yaw.

NORMALLY, deeper wheels are faster as you get into higher yaw angles.

---

"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

thanks Jordan.......i think it was the Hed 3 that threw me, since it does better than their deeper wheels at more yaw. now that i compare their 60 and 90 though the 90 still does better all angles