I have been interested in the Conti Podium, cheaper than most TUFOs but I don’t know anything else about the tire. It seems to be the tire that is left out of all of the tests.
jaretj
I’m wondering about the bulge theory. Rick: do your 404s have the ‘bulge’?
Yes, my 2001 404 is the first-generation bulge rim. Zipp has changed the shape of that bulge on the newest 404s. To the casual glance, they look the same, but the bulge is moved a little back toward the spokes.
BTW – the tire on the 404 is slightly narrower than the fattest part of the rim (1-2 mm). The tire on the 808 is exactly the width of the widest part of the rim.
I remain inconclusive over the CdA issue. Not that there isn’t a difference – I just find it impossible to believe that it is as large as the Lim regressions indicate. Further, a CdA difference as high as 0.04 has some truly outrageous implications for rolling resistance differences. It would mean that a single Tufo tire makes the bike more than 30-40 watts harder to push along. I find that impossible to believe, too. And, my race experiences with that single 404/Tufo wheel on the bike don’t support that contention. Again, I think the Tufos are slow, but not that slow.
Despite all my efforts to get clean data, this data set has its drawbacks. I think it is clearly robust enough to make my main conclusion. Even if we add in quite a bit of uncertainty to account for wind, temperature, hubs, tire widths, etc, the gap is too large to ignore, and it was large under the whole range of conditions. If the vagaries of testing conditions were prone to throw the results, why did they throw it to the 808 on every single trial?
People are always asking for “real-world” tests, and like to pooh-pooh controlled indoor tests. Well, what do you want? 20 (18) laps around an actual TT course under as controlled conditions as one can get. The gap between these setups is just huge.
I’m tempted to go with the podiums but I’m a 650 guy.
jaretj
At this point what tire would you go with to match '04 404’s? I have races coming up and need to decide soon. The roads around here aren’t the best so I’m not sure about going with 19mm’s.
I was going to glue Tufo S3’s on today but now I think I’ll change.
The Vittoria EVO CX’s that I tested worked well. Josh at Zipp as mentioned that they wind tunnel tested well also. If you can find them Zipp makes a great tire to consider.
Anyone else? I need to order some today.
Excellent work there Rick. Anyone viewing the body of evidence at this point would be foolish to ‘stick’ with their Tufos. If I remember correctly, doesn’t power required to overcome Crr go up with both speed and weight? Seems like you are actually being kind to them by testing just the front wheel (less weight on the front wheel) at low speeds and at your weight (160ish?).
I’m not sure what to make of the CdA difference you found between the 808s and 404s but I do feel good about buying the H3 front clincher now…you called the tri-spoke “dead tech” right? 
Now I want all my 2004 races back…I’m thinking 15-20min better IM bike split, 2min for Olys and 10min for the 1/2 IMs…hmmmm.
ot
I don’t know anyone who rides TUFO’s that only inflate them to 115 psi.
Non-scientific and don’t know how much difference it would make, but they do seem to be sluggish at lower psi. Don’t know why - maybe it’s the tubeless design, but they seem to need at least 140 psi to “feel” the same as a clincher setup at 115 psi.
In my tests, the Tufos did even worse at higher pressures. I think the tests smwrdrm did showed the same thing.
–jens
I tested them at 115psi and 150psi they did worse at 150psi. I only published the 115psi data.
I concur on the CXs, though I would slightly prefer the KS, which is the same tire with a slick tread. No one has ever demonstrated an advantage to having tread on a bike tire – in wet or dry conditions. The rec.bicycles.tech FAQ has a long discourse on this…
–jens
You could also do some testing at an indoor track (i.e.: Burnaby Velodrome). removes a fair amount of variability (but not all as most of it is from the rider).
AP
As promised, I am posting the results of some field testing I did comparing two different front wheel and tire setups. The results were both as expected and not as expected.
The two wheel setups were:
Zipp 404 (2001 model) shod with tubular Tufo S3, size 21. Glued with Continental glue about one year ago. The gluing job at that time involved a full cleaning of the rim, multiple coats, etc. That wheel+tire has been trained and raced on 4-5 times in the past year for a total of about 150 miles. It has been stored inflated. It does not have sealant in it. To the casual observer (me) the tire looks virtually new.
Zipp 808 (2005 model) sporting a clincher Michelin Pro Race, size 23, with standard weight inner tube (Specialized). That tire has about 1,500 miles on it.
Bike setup was my Yaqui DE, size 55 TT bike. Rear wheel was PowerTap hub on OpenPro rim and Michelin Pro Race size 23 clincher. No water bottles; two frame cages. Both tires at 115 psi. No adjustments made to any bike fit parameters during testing window.
I wore the exact same clothing for each trial – snug sleeveless tri-top, basic bike shorts, Bell X-Ray helmet, TriVent shoes. No arm warmers or leg warmers.
Trials took place in three batches in a six-day window. Course was Fiesta Island “short loop,” which is 2.5 miles, give or take 50 meters depending on exactly where I hit the interval button on the PT computer. I measured single laps, stringing together 1-3 in a row on each wheel before changing wheels. Each lap began with a flying start at about 20 mph, holding a given power output target for that lap. Each lap was completed at a constant power. For example, I would do a whole lap at ~175 watts, then start over for the next one at, say, 215 watts. A total of ten laps were completed for each wheel+tire.
Conditions ranged from a barely perceptible breeze to dead calm. I did each set at 5:30 to 6:30 am, and quit before the sun got up in the sky and kicked up the wind. Road surface there is fairly good – about what you’d expect on most N. American Ironman courses. Slight rise and fall of ~20 feet per lap.
I recorded the average watts and average speed off of the PT computer display. I was not able to complete downloads into CyclingPeaks on all of the runs, so I used the PT computer data. More on that point later.
The data:
404+Tufo
Power Speed (mph)
162 19.5
205 21.6
173 20.6
165 19.6
183 20.3
210 21.9
164 19.7
214 22
235 23
808+Michelin
Power Speed (mph)
173 21
211 22.7
222 23
215 22.9
190 21.8
188 21.6
160 20.5
242 23.9
245 23.9
A casual examination of these figures should convince anyone that the 808 setup is much faster (at the 99+% confidence level). It’s not even close.
The big question is, “Why?” Is it the tires or the wheels? Let’s first talk about the wheels. Zipp has published figures that indicate that the 2001 404 is about a half second per kilometer slower than the 2005 808. In terms of my data accuracy (tenths of a mile per hour) that is barely measurable. While I had intended to make an exacting adjustment to the data for the drag differences between the wheels, I think it is a waste of time to do so. The differences overwhelm an adjustment that small.
So, I start by assuming that the entire system of bike and rider had the same CdA for all trials. (If Josh at Zipp thinks this is a bad assumption, please feel free to say so…).
With full credit to technical assistance from my mate from the Great White North, rmur, assuming a CdA of 0.27 and some other constants, we would estimate the Crr’s to be:
404+Tufo: 0.0073
808+Michelin: 0.0050
This is equivalent to a 15-20 watt differential to travel the same speed. Note that these Crr estimates are for *both tires being the same. *In the case of the 404+Tufo setup, all of the difference is attributed to only one tire. In other words, these figures understate the Crr for the Tufo tire. Under our assumptions here about CdA, the Tufo is actually somewhat worse than 0.0073, and the wattage penalty for the Tufos is somewhat worse than 15-20 watts. Throw in a small speed adjustment for the 404, and maybe we get some of those watts back. But just a little. The difference here is 10-12 minutes in an Ironman, my friends. And that’s just one of two tires.
I could leave it at that and claim to have proved a point, but there is a puzzling anomaly that bears reporting.
In the method above, we made a (perfectly valid, IMO) assumption that the CdA was near-constant for both setups. It turns out that we can test that assumption. Via a method published by Allen Lim, one can analyze these types of trials at varying speeds and power levels and extract CdA and Crr separately. Kraig Willet was kind enough to crunch the numbers for me and show me an odd result.
According to the Lim method, the 404+Tufo trials exhibited a materially lower CdA than did the 808 setup trials. While we assumed above that they were the same, or that, at most, the 404 was a little slower, the data tells us the “slower” wheel was faster in terms of CdA. How much faster? A CdA of 0.24 versus 0.28. If you didn’t realize it, this is a shocking gap.
This has two serious implications. First, if it is true (and I don’t think it is), Zipp better go back to the wind tunnel! If it is true, it means that the Tufo tires performed far, far worse than rmur estimated. The Crr had to have been so bad as to overcome a profound aerodynamic advantage held by the 404 wheel. While I am convinced the Tufos performed badly versus the Michelins, they cannot be that much worse! Knobby mountain bike tires maybe, but not the Tufos.
The second implication is that the data has some flaw in either the way it was gathered or the way it was computed and recorded. The only “gathering” flaw would be if I had held the aero position while on the 404s and sat up while on the 808s. I assure you that was not the case, so we must look elsewhere.
Two possibilities: First, I discovered that the PT head unit reports average power and speed figures that are slightly different from the averages one gets if one downloads the data and analyzes the raw file. Average power and average speed are sometimes under-reported on the head unit, versus the data actually recorded on-the-fly. The differences are in the 0.4% to 1.1% range, and I cannot discern a pattern. So, it is possible that, by reading the results off the PT head unit instead of from a download, I have flawed data. It is unlikely to affect the basic conclusion from the first half of my discussion because the possibility of mis-calculated average figures would seem to apply equally to both wheel setups. While these changes might be enough to throw off the regression results from the Lim technique, they are quite unlikely to throw off the basic conclusions.
Second, Lim’s method argues for lots of data points. In particular, it begs for additional data points from low-power, low-speed trials. My slowest trial was 19.5 mph at 162 watts. Lim did trials starting at 100 watts in his paper. Kraig has suggested I go do a few more low-speed trials. I think I’ll do that and see if the Lim formula spits out results that are a bit closer to what we might expect. It is an open issue that needs resolution. It is, quite frankly, impossible that the 404 setup reduces the CdA of the entire bike + rider system by a whopping 0.04.
So, what do I conclude?
This and only this: A 2005-era Zipp 808 clincher front wheel mounted with a Michelin Pro Race 23 mm tire requires 15-20 less watts to push along at a given race-level speed than a 2001-era Zipp 404 tubular front wheel mounted with a Tufo S3 21 mm tire, on a bike set up as described, and piloted by me.
Of that much, I am quite certain. The data is overwhelming, and there is no room for the null hypothesis.
What I am less certain about is how much of that difference is strictly due to tires. I have an overwhelmingly strong hunch that it is all in the tires. But until I run some more trials, the Lim calculation leaves me scratching my head.
Questions?
Also, you state that a total of 10 laps per tire & wheel combo were done. However, you only show data for 9 data points each.
Thanks to the highly refined observation skills of Uncle Phil, I have added the mysteriously missing 10th trials of each wheel:
404+Tufo:
170 watts; 20.3 mph
808+Michelin
165 watts; 20.3 mph.
Somehow, I just knew I had done a few more low-power runs. When I did my copy-paste on biketechreview I left off the bottom row from my spreadsheet.
This doesn’t really change anything other than the regressions. Instead of slopes (CdA) of 0.241 (404+Tufo) and 0.281 (808+Michelin), we get 0.247 and 0.263. A closer relationship that does much to alleviate my panic over the CdA differences!
The intercepts also move closer together at 6.983 and 4.403 (the intercepts are directly proportional to rolling resistance). If we assume the Michelin pair at 0.005, the Tufo + Michelin pair would be at 0.0079. That seems on the high side (for only one changed tire), but is not inconsistent with what rmur calculated.
Further data points at lower powers (100, 125, 150) would give us higher confidence in the resulting CdA measurements. Whether I go out there and do more laps is another question though.
If I do more trials, it will probably be to test the 808 with the size 20 Michelin and maybe the Pro Race Lites with latex tubes or something. This takes a lot of time, so my efforts need to be spent trying make me faster, not all of *you. *
Thanks for all the input.
… doesn’t power required to overcome Crr go up with both speed and weight? Seems like you are actually being kind to them by testing just the front wheel (less weight on the front wheel) at low speeds and at your weight (160ish?).
Crr should be constant across modest changes in speed. In theory, a tire will get hotter (altering Crr) at high speeds, but the difference is likely quite small at these small speed variations.
I did a front-rear weight distribution test. In the aerobars, I have 53% of my weight (162 lbs) on the front wheel. This is in contrast to a normal roadie position which might only have 40% on the front.
Ok…Crr is unit-less but power required to overcome Crr appears to be directly proportional to speed (and weight). From Rmur’s equation posted in another thread:
Actually Power to overcome rr, Prr = Mass (kg)* G (m/s^2)* Crr (unitless) * Ground speed (m/s)
ot
Interesting study and I’m curious of course, but I don’t know about all this. When I first got my 404 tubulars I put Tufo Jet Pros on and rode them for about a year and a half. Got two flats in two IM qualifiers and that was it for the Tufos. Judging from what I pulled out of the tires, I would have flatted with anything but mojo is mojo and they now have bad mojo with me. I then switched to Vittorias and found I like the feel of them on the road a lot better than the Tufos. But are they faster? Here are my real world IM bike splits for 3 years over the same course (Blue Devil):
2002: 5:22 P2K, 404s with Tufos (warm with periods of rain, rode .5mile+ extra…missed a turn)
2003: 5:18 P2K, 404s with Vittorias (chilly with some drizzle)
2004: 5:17 P3, Disk rear with 404 front both with Vittorias (very cold and windy)
I don’t use a powermeter or HRM so I don’t have any watts/HR comparisons to go with these times. It could be that I saved a few watts with Vittoria’s but I know I felt equally crappy at the start of the marathon…as one should in an IM ; )
So in my rather unscientific experience, even though I love the Vittorias, I can’t really say that the Tufos were exactly costing me any time either.
Keith