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20s vs. 23s -- Where's the data?(13 posts)

20s vs. 23s -- Where's the data?jtolleson
Sep 10, 2002 12:31 PM
A debate raging on another site of the oft-visited debate over rolling resistance between these two tire sizes.

I've often heard folks talk about studies comparing the contact patch of the two and the counterintuitive conclusion that the 23 has less rolling resistance, but does someone have a citation or link for that info?
here's a startDougSloan
Sep 10, 2002 3:04 PM
http://yarchive.net/bike/rolling_resistance.html

I'll check some more
moreDougSloan
Sep 10, 2002 3:22 PM
http://draco.acs.uci.edu/rbfaq/FAQ/8b.14.html
and moreDougSloan
Sep 10, 2002 3:24 PM
http://www.terrymorse.com/bike/rolres.html
So what are YOU running? ;-)Humma Hah
Sep 10, 2002 4:19 PM
I'm rigging the Paramount with 32mm initially, figuring I need a little meat until I get used to roadbikes. Pinch flats will probably slow me down more than rolling resistance.

I'd tend to agree with the opinion that tire width has almost nothing to do with tire rolling resistance, but that flexing thick sidewalls, stiff rubber, and squirming tread are the worst culprits. That agrees with my own perceptions in trying numerous types of tire. MTB knobbies are way draggy on the road.

On the other hand, the cruiser will outrun most roadbikes on a brisk coasting downhill. Whatever rolling resistance the 1 3/4" balloon tires produce is overcome by my ability to get in a really tight tuck on the bike. Aerodynamics are the big theif in cycling, and the human body is the culprit.
23's mostlyDougSloan
Sep 10, 2002 7:02 PM
I use almost exclusively 23's, but run 25's on the track bike and 28's on my old Bianchi for rough roads; I'll throw on 35's for the worst parts of the 508, where the roads can swallow up 23's.

I'll never, ever use 20's again. I got too many pinch flats. Rolling resistance is pretty irrelevant when the tires flat too often or ride like hell from over inflation to avoid it.

Doug
23's mm tires at 110-115 psi are a sweet rideMaartin
Sep 11, 2002 11:17 AM
Based on advice from people on this board I am using this setup and it is great. No need to be at 125 psi. very smooth
uh...the tires listed here are over a decade oldspookyload
Sep 10, 2002 4:29 PM
don't you think the changes in sidewall composition and rubbder composition could slightly skew this data. Secondly, what difference on acceleration does the extra weight(most times around 20grams per tire)have in relation to the lower rolling resistance. By this I mean does the reduced weight make up for the additional rolling resistance. And lastly, does the higher pressures the 20mm tires will let you run make up in any way for the rolling resistance gained by the 20mm tire.
uh...the tires listed here are over a decade oldChainstay
Sep 10, 2002 7:40 PM
Not to mention the higher aerodynamic drag of the 23mm tire vs the 20mm. I read somewhere that this can become significant to triathletes or time trialists but not likely to a club rider or road racer.

Still, I ride 23mm for the ride comfort and the fatter rounder profile feels a lot more stable and secure while cornering. The Conti 3000 23mm clincher on my Ksyriums compares to the Clement Criterium tubulars I have on my Cinelli for ride feel.
Intuitive, not counter intuitiveKerry
Sep 10, 2002 4:50 PM
At the same inflation pressure, any tire size will have the same contact patch on the road. This ignores the stiffness of the casing, which is reasonable since the tire casing has minimal strength compared to the 8 or so bar pressure in the tire. Since the contact patch is the same size, a skinnier tire will have to flex more than a wider tire. More flex = more energy dissipated in the casing and rubber = more rolling friction. However, skinny tires are almost always inflated to higher pressures, so this effect is largely canceled. Narrower tires are very slightly more aero, and otherwise (when inflated to higher pressures) about the same as wider tires. With wider tires you get better traction, a more comfortable ride, and better pinch flat resistance. Hence the argument for wider tires. However, very wide tires typically have much stiffer casings (not built the same as their 20, 23 or 25 mm brothers) and so they are not a good choice either. Optimum performance for most people is 23, with 20 OK for very light riders and 25+ for heavy riders. After that, it's personal preference.
re: 20s vs. 23s -- Where's the data?koolaid
Sep 10, 2002 7:44 PM
What's the name of the other site? Is it a board that actually welcomes women? It seems every time I check this board now women are being either patronized, made fun of because of the way they look, called dykes, or at the other end of the spectrum photos of models are being drooled over.
www.bicycling.comjtolleson
Sep 10, 2002 8:16 PM
I would say that women are definitely welcome, maybe even nearly 50 percent of the mix. But there's a trade off there. I think it is a younger and perhaps slightly less experienced mix. There are a few excellent resources who are regulars there, but I also think you have to sort through more bad info there (and even more repeat questions than here).

I visit both. Balance and harmony in my life!

Oooommm Mani pad me Ommmmm
Thankskoolaid
Sep 10, 2002 9:16 PM
I'm always trying to find that Jewel in the Lotus too! : )