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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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.
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Re: Zipp Aero Data- finally- comparing data with rider [rik] [ In reply to ]
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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

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.

Last edited by: mlinenb: Apr 5, 08 7:23
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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not angry at all- just fact finding.... so here's some more interesting data....

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
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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.
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Re: Zipp Aero Data- finally- comparing data with rider [Tom A.] [ In reply to ]
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You also may want to consider the negative aero effects of the "lip" on a glued-on tread type tire (like the VF)

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?
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Re: Zipp Aero Data- finally- comparing data with rider [Andrew Coggan] [ In reply to ]
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In Reply To:
You also may want to consider the negative aero effects of the "lip" on a glued-on tread type tire (like the VF)

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/
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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?
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Re: Zipp Aero Data- finally- comparing data with rider [Record10Carbon] [ In reply to ]
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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?

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/
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Re: Zipp Aero Data- finally- comparing data with rider [Tom A.] [ In reply to ]
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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....

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.
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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 | Facebook - Rappstar Racing | @rappstar | I work @ Zwift

Ask me about: DiamondBack Bikes | Zipp | 1st Endurance | Normatec - $100 off RAPP2017 | Quarq | SRAM | MatchRider | Kiwami | ROKA
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Re: Zipp Aero Data- finally- comparing data with rider [Record10Carbon] [ In reply to ]
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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?

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
Last edited by: rik: Apr 7, 08 10:02
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Re: Zipp Aero Data- finally- comparing data with rider [mlinenb] [ In reply to ]
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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.

Josh
http://www.SILCA.cc
The 3 Keys to Super Easy, Super Fast Tire/Tube Installation (even with latex):
https://www.youtube.com/watch?v=9W85RCHoukI
How much speed and comfort is your tire pressure costing you? More than you think! https://silca.cc/blogs/journal
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Re: Zipp Aero Data- finally- comparing data with rider [joshatzipp] [ In reply to ]
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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.

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.
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Re: Zipp Aero Data- finally- comparing data with rider [rik] [ In reply to ]
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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?
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Re: Zipp Aero Data- finally- comparing data with rider [Andrew Coggan] [ In reply to ]
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In Reply To:
You also may want to consider the negative aero effects of the "lip" on a glued-on tread type tire (like the VF)

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?
Yes.

Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)
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Re: Zipp Aero Data- finally- comparing data with rider [damon_rinard] [ In reply to ]
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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?
Yes.
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.
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Re: Zipp Aero Data- finally- comparing data with rider [damon_rinard] [ In reply to ]
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In Reply To:
In Reply To:
You also may want to consider the negative aero effects of the "lip" on a glued-on tread type tire (like the VF)

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?
Yes.

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/
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Re: Zipp Aero Data- finally- comparing data with rider [Andrew Coggan] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
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?
Yes.
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.

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)
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Re: Zipp Aero Data- finally- comparing data with rider [damon_rinard] [ In reply to ]
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In Reply To:
In Reply To:
In Reply To:
In Reply To:
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?
Yes.
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.

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.

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/
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Re: Zipp Aero Data- finally- comparing data with rider [Tom A.] [ In reply to ]
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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)
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Re: Zipp Aero Data- finally- comparing data with rider [damon_rinard] [ In reply to ]
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"4. All tires were run in the tunnel on the same wheel: Bontrager ACC."

How wide is that wheel?
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Re: Zipp Aero Data- finally- comparing data with rider [damon_rinard] [ In reply to ]
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In Reply To:
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.

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/
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Re: Zipp Aero Data- finally- comparing data with rider [vjohn] [ In reply to ]
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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)
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Re: Zipp Aero Data- finally- comparing data with rider [Tom A.] [ In reply to ]
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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)
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