Why hasn't anybody done this test?

Triathlon Forum
1

I find myself quite intrigued by the whole clinchers vs tubular debate (please don’t turn this thread into an argument for or against either). There is great evidence in favor of each. I don’t know that I buy the rolling resistance data in favor of clinchers on a steel drum (roads interact differently with a tire than smooth steel does), but it’s interesting data. What I’d like to see is the following test:

Many people ride a weekly TT put on by a club. I do one most weeks that is 11.75 miles and ride at 100% effort (drooling).

Ride the course weekly for a couple months alternating similar wheels clincher/tubie.

For example, week 1, Zipp 404 clincher. Week 2, Zipp 404 tubie and so forth.

After a couple months, which wheelset produces the fastest time? Are the times comparable, or does one set consistently outperform the other?

The above test would provide strong anecdotal evidence that one type of wheelset is either faster or the difference is nil. It would also help to negate weather effects and training effects since it is repeated several times over a long period of time.

Other combinations that could be tested: Hed3’s clincher vs tubie. Hed Jet vs Stinger.

I own a Renn disc and Stinger 60 front, both tubie. If anyone wants to lend me a Renn clincher and Jet 60, I’d be happy to do the test and announce the results : )

2

(…) The above test would provide strong anecdotal evidence (…)
And a new oxymoron is born. Congrats.

3

Probably someone has done that test. Lots of tests have been reported here in the past. If you want real world tests of clinchers vs. tubular, a better test might be an uphill test (slow speed so aero effect is minimized) using a powermeter. That’s been done. Search for posts by Jens and Tom A. I believe those two guys are expert in aero/power/rr testing.

I too posted here a long time ago that a steel drum is different than road. Tom A. patiently explained to me, and to others many times since then, how the drum is a good test. A good thought experiment is to ask yourself why a tubular, which takes more energy (vs. clincher) to deform and return to shape on a drum, would take less energy (vs. clincher) to do so on a road? Both should perform better on road than drum since it is a flat surface. Yes, roads are also irregular and bumpy. But wouldn’t the tire that deforms with least loss of energy be the best in dealing with the bumps in the road?

4

The reason no one has done that test is because there are so many uncontrollable variables (weather, diet, rest, health, traffic, increasing or decreasing fitness, plus many others I’m sure I didn’t mention). You wouldn’t learn anything from that test.

5

LOL! Nice!

To the OP - yes, too many variables to control to draw any meaningful conclusions from. Actually, if you did said test, carefully, recorded the times, etc. you would not likely see a significant P value.

Also, again, if one tire has a smaller Crr on the “steel drum” I’m not sure why you think it will magically “switch” on the road. You seem to be confusing the coefficient of friction test vs. bike speed - NOT the same thing!

6

Yes, I know there are many variables, but with repetition, variables tend to cancel each other out. I find it hard to believe that the fastest combination (if one is measurably faster than the other) wouldn’t make itself apparent. I’ve seen it happen in my own experiences. For example, I typically ride the same TT time give or take 15 seconds (same course). If I Add an aero wheel vs a box rim, I’m consistently a few seconds faster than the box rim time, no matter what the weather, effort, rest, etc. The same is true if I wear a tight fitting shirt vs one that is a little baggy, I’m a CONSISTENTLY a few seconds faster with the tight shirt. If clinchers WERE faster, I would think that over time, my fastest times would be put down with the clincher wheels. My opinion is that you would see little to no major time difference between the two and thus could put the rolling resistance argument to rest. Ok, I’m at a bachelor party now and and gonna go have fun, so no more arguments till tomorrow…

7

Yes, I know there are many variables, but with repetition, variables tend to cancel each other out. …

A common misconception. Too many uncontrolled variables make the results entirely unreliable – the bad variables don’t just cancel each other out, they also drown out any useful information. Even more importantly, they cause the experiment itself to be *misspecified. *A badly designed experiment with good data collection is still a bad experiment.

The most important variable that has to be controlled is the cyclists’ effort. Over the course of a season, on identical bikes and tires, our times can easily be in a 2-3 minute window over even a short race like a 20k. That is due to the weekly rise and fall in fitness. There is no way you can make reliable aero or tire decisions with that much movement in power output. HR monitoring is pointless, since power output will rise and fall, at the same HR levels, all season long.

What *has *been done that involves a well-specified experiment is to ride identical courses under the same conditions, with a powermeter. By “same” conditions, we mean without hills and without wind. Tires have been tested on the track by numerous publications and hobbyists. Tires have been tested on road circuit under carefully controlled conditions by various investigators (myself included). They all come up with the same results as the guys testing on drums. (As an aside, know how Michelin tests F1 race tires for Crr? On a drum. Why? Because it works.)

What puzzles me is that, no matter how the test is designed, the retro-crank tubular folks will always chortle and dismiss the test. Test on a drum, they say “not real roads”. Test on a track, they say “not on asphalt.” Test on an asphalt road, and they just say “I don’t believe the test.” Hmm.

Every test and every set of conditions leads to the same data result. Still, there are those who will never believe that a clincher can be as fast as a tubular, for the sole reason that, “If clinchers are so fast, why do pro cyclists ride tubulars?” I can’t answer that question, but I can wonder why anyone would put the decisions of a pro cyclist on a pedestal. Isn’t it sort of obvious by now that pro cyclists, as a group, aren’t the wisest and most thoughtful athletes around?

*All that given – *The reason some of us started doing these tests is that we DID see differences in our race times between the two tire types – differences that couldn’t be readily explained. With the same power output under similar circumstances, we couldn’t figure why our times didn’t make sense. A few summers ago, I was scratching my head when my race times with 404s and tubulars were worse than my practice times using training wheels and clinchers. I rode the same course a few times a week, training with a powermeter. Then I’d do the race on the same bike, with the same powermeter, using my expensive wheels and tires, and end up with slightly worse speeds at given power levels! On other forums, I met people finding the same thing going on. We started running tests and every person came up with the same facts.

Those facts lead to a simple conclusion.

8

Forgive me, I omitted Ashburn from my post above. Rather than debate testing, tubulars/clinchers, etc, why not learn first. Search this forum and you’ll find a bunch of good stuff. Here’s one to start with: http://forum.slowtwitch.com/gforum.cgi?post=390031;search_string=latex;#390031
.

9

Hello Triocd and All,

Here are some thoughts:

http://forum.slowtwitch.com/gforum.cgi?post=1058545#1058545

Also someone in Colorado Springs has a moving belt (like a tilted treadmill) that you can put your bike on for controlled coasting testing. ( and you could add different surfaces)

Cheers,

Neal

10

I was going to mention the moving belt test, I also love to point out Olano’s rainbow jersey as one reason pros still glue 'em on.

http://youtube.com/watch?v=HOtqNQJQcuU

This is an incredible video if you’ve never watched the “hammer throw” from the '95 worlds.

Personally I’ve got an 8th i/o a DNF and both collarbones intact from tubulars, so I’ll take the Crr increase.

-SD

11

Hello SuperDave and All,

Great video from 1995. Great ride finish on a flat. As you say, you probably could not do that on today’s clinchers.

To each his own. Having just changed over from tubulars a year ago I will still stick with clinchers for now.

I hope you know Tufo tubulars have a butyl lining and do not need to be pumped as frequently - also with Tufo sealant they are fairly flat proof. :slight_smile:

Just kidding… I have wondered about my low Crr and smooth rolling clincher coming off on a steep descent and rolling me up in a ball.

I have had a clincher blowout - front tire - on the flats and straight ahead - no problem, but only doing about 20mph.

It would be interesting to test a clincher blowout on a high speed turning descent - but where would we get test pilots?

We could use a small remote charge to blow off the valve stem and high speed photography to record the effects.

Until then we will have to rely on clincher rider reports … and I have only heard a few … none with major loss of control.

Cheers,

Neal

12

Until then we will have to rely on clincher rider reports … and I have only heard a few … none with major loss of control.

Cheers,

Neal

Last summer I blew a rear tire coming down South Park Drive in Tilden Park (Berkeley Hills) going over 40mph, on a barely-holding-on curve near the bottom. It was sketchy for a few seconds, but I made it to the side of the road with the shiny side up.

I had to sit down for a few minutes – I was shaking so bad I couldn’t fix the flat. :-p

13

Hello Ashburn and All,

Makes me nervous reading about your narrow escape. Glad you made it. Combination of skill and good luck.

There must be some more stories out there of riders losing a clincher front tire on a curving descent.

**Maybe we haven’t heard many of those stories because the riders are not here to tell them. Or because tires do not fail at inopportune times? ******

Have you heard any other descent tire failure stories or narrow escapes?

Cheers,

Neal

14

I was decending Parawan Canyon from Brianhead Ski resort once (Southern Utah) and hit a groove in the road gouged by some large construction vehicle. Double pinch flat at about 35 mph. That was white knuckle for a bit. Still, I slowed down to a stop without crashing and hitched a ride home with the park rangers.
Just my suspicion, but I doubt many triathletes glue their tires on hard enough to prevent them from slipping given a catastrophic loss of air.
Chad

15

Hello Cdw and All,

Again, skill and good luck win out!

Clincher or well glued tubular?

Cheers,

Neal
.

16

I have seen a number of people get blowouts on the track. I have NEVER seen anyone stay up riding clinchers, but I’d say the tubular users saved it about 70% of the time.

At one of the practice sessions from last year’s world cup, one of the Aussie riders using Vittoria Ulra Speed tires and Mavic’s Ellipse wheels got a flat at the top of the 43 degree banking and got some pretty nasty floor burn. I don’t recall who it was, but it couldn’t have helped his chances for a World Cup win.

-SD

17

Hello SuperDave and All,

Your observation of saves with tubulars vs crashes with clinchers is worrisome news for the clincher users like me when we are ripping down a hill on a clincher.

I think you are right on tubulars being best for track riding.

First of all you can use very hard glue (shellac) that will help Crr.

(And if the flat tire is glued on so tight you cannot remove it on the track that is not the same difficulty of problem as fixing that tire in a triathlon race.)

Also you get the best Crr on a very smooth surface with high tire pressures which calls for tubulars.

Cheers,

Neal
.

18

That was exactly my thinking switching to tubs. I was a somewhat fearful decender anyway, had a good accident, and nearly died with a double flat on clinchers coming on the backside of the Presidio on the Alcatraz course (I have NO idea how I managed to stay up on that one). Wanted good racing wheels and just had to go with tubs.

19

Hello Tildenm and All,

Glad you could save it and even though you switched to tubs it puts another save for skill, cunning, and good luck to clinchers.

Cheers,

Neal
.

20

Clincher tires have been improved over the past several years resulting in the lower crr. But the tubie tires are now getting better. Tubies usually allow more air pressure lowering resistance. I ‘suspect’ that the best tires these days will be comparable to each other whether they are clincher or tubie. But the tubie safety argument is important. Also, you may be able to finish your race on a flat tubie but not on a clincher.