Comparing CRR Numbers

[jslopez93]

So say I do a coast down on 2 similar set ups. Difference being the Wheels (Am Classic Clincher 420s vs Am Classic 38 Carbon Tubulars). Doing the 10 coast down 4 mile rides for both in the same area (granted different days), my CDA is the same but CRR is Higher for the tubulars (.0091 tubulars .0015 clinchers). Is this telling me that the clinchers are actually the faster wheelset/set up?

Only thing that would explain that for is the fact that the tubular tires currently have the anti flat slime (put in by the previous owner) and the tires are older.

Thoughts?

[coachboyd]

.0091 for tubulars seems kind of a high crr number *UNLESS* these are Tufo HICC tubulars (very well could be since you say you have the sealant in them). Another thing that will give you a higher crr number is the Tufo tape. I know it's easier, but it's not making you any faster. So, if you have older worn Tufos with tape and sealant, I could see this number being right.

For the clinchers, that crr seems really low and unless you did the ride at 180 PSI on a wooden velodrome, I think you are a bit off there. My Michelin clinchers give me a .0048

Scroll to the bottom of this list for a good idea of crr ranges
http://www.velonews.com/article/12493

And get a good set of handmade Italian tubulars!!

[jslopez93]

interesting.

I was really thrown off by yesterday's TT performance. 10 seconds slower last week but higher watts (244 vs 254). No noticeable headwind this week so I was almost going to say ibike error.

Last week I had the clinchers and this week the tubular with the carbon tubulars (with old tufo tires/sealant). Would it be safe to say that this is telling me to either get better tubular tires or go clinchers from now on?

[Site_Admin]

Clincher technology has come a long, long way. Travis and I spoke about doing maybe 2 days' worth of CD's on different wheels, tires, and on different surfaces, and then writing it up. I DID do this a looooong time ago in the late summer of '06, with different tire pressures, and I sort of found out that my 'sweet spot' on tire pressure was something like 102-105psi. Still, this took a long time, it took a ton of CD's, and it was on a PC that I don't even own any longer.

We will try this again, but let us get the other stuff out first, then we can worry about esoteric stuff.

[Isaias]

Some links of interest:

http://www.rouesartisanales.com/article-1503651.html (skip to the bottom for thumbnails linked to tests for tubulars and clinchers, respectively)

http://www.biketechreview.com/tires/ima ... g_rev4.pdf

EDIT: Sorry coachboyd, missed following Zinn's referenced link about rouseartisanales.

[coachboyd]

A lot of people are on the clincher high right now, and while they are easier and have a lower rolling resistance. . .there is nothing like that sweet ride on a good set of tubulars. There's also a good weight savings and without the risk of a pinch flat you can run them at much lower pressures. I'm not sure how many crits you guys are doing in the pouring rain, but I would never want to do one on ANY set of clincher tires.
Time trials - clinchers would be ok
Road races and crits - There is more important things than a couple watts.

[Isaias]

A lot of people are on the clincher high right now, and while they are easier and have a lower rolling resistance. . .there is nothing like that sweet ride on a good set of tubulars. There's also a good weight savings and without the risk of a pinch flat you can run them at much lower pressures. I'm not sure how many crits you guys are doing in the pouring rain, but I would never want to do one on ANY set of clincher tires.
Time trials - clinchers would be ok
Road races and crits - There is more important things than a couple watts.

I know you stated "good set of tubulars", but what's your feelings about Tufo tubular clinchers?

I know that with tubular clinchers you won't experience the weight savings factor, since one still needs clincher wheels (w/a clinch bead that makes the wheels heavier) and the clinch block on the Tufo tires adds more weight--it works out to be a break even situation in comparison to 100% clincher set-up regarding weight.

Personally, I like that there's no pinch flats, one can run them at lower pressures due to their construction, the tire tends to stay on the wheel after a bad puncture, and in a pinch you can ride them flat (I had to ride a flatted one for 10 miles once.)

[jslopez93]

A lot of people are on the clincher high right now, and while they are easier and have a lower rolling resistance. . .there is nothing like that sweet ride on a good set of tubulars. There's also a good weight savings and without the risk of a pinch flat you can run them at much lower pressures. I'm not sure how many crits you guys are doing in the pouring rain, but I would never want to do one on ANY set of clincher tires.
Time trials - clinchers would be ok
Road races and crits - There is more important things than a couple watts.

Made a discovery on Sunday that may prove the above point. I was riding (on the tubulars still) doing a recovery ride and halfway thru the ride I realized that my front tire had a slow leak eminating from the valve stem which, if it was happening all weekend, would explain the strange/low numbers. Sucks in terms of performance but the fact that I was able to do the TT and an road race next day on was a semi flat tire, kudos to tubulars.

I'm putting on a new set for next weekend and will see if the CRR numbers change a bit.