niccolo wrote:
Canadian wrote:
niccolo wrote:
FatandSlow wrote:
niccolo wrote:
On their rims, optimized for the 23mm GP4Ks, Flo now recommends the 25s if they fit the bike because at the same PSI, their rolling resistance advantage should trump their aero disadvantage. But it's not clear to me that at both tires' optimal PSI, that's still true (though the Flo guys are savvy, so you'd think they'd have considered this). And I suppose road surface should factor in, too. Presumably Flo will update their recs based on the analysis they've been doing recently.The key words here are, "at the same pressure." Most folks seems to be running their 25s at lower pressure than their 23s for comfort. My personal ass-o-meter tells me that 25s pumped to the same pressure that I run 23s on rim from old narrow Reynolds Assaults, to Flo 60s and ENVE3.4s loose all their "comfort advantage." I've done this with Continental GP4000sii and Michelin Pro3 and 4 tires. I run the Reynolds at 105 front, 110 rear, the FLOs at 95/100 and the ENVEs at 90/90.
Of course, this is just my ass-o-meter and it probably isn't calibrated to be of assistance to anyone else.
I do run 25 on Hed Belgium C+ rims and am planning on running them on the Hed Jet 6+ wheels I just purchased.
Personally, I think the key words here are "at both tires' optimal PSI." I don't much care that if you arbitrarily set the PSI the same, the rolling resistance of the bigger tire is lower. It's more impressive if the rolling resistance is lower when casing tension is matched. But what I really want to know is, at the PSI that yields the lowest rolling resistance, for each tire individually, how do those rolling resistance values compare?
Of course, road surface factors into this.
And once we can actually compare rolling resistance in an appropriate way, then others factors, particularly aerodynamics, need to be factored in also.
It's kind of odd to me that we still seem to be in the dark ages of understanding tire performance. How do savvy folks like the Flo brothers, and lots of others, still compare tires "at the same PSI" when the same PSI in a larger tire yields a higher casing tension? It almost makes me feel like I must be missing something...am I?
You're definitely going to want to run larger tires at lower pressures. As you said, it's more about casing tension than it is tire pressure. We are still putting a ton of data together but we hope to have a much better pressure guide for our customers in time.
FatandSlow, your ass-o-meter is right on the money ;)
Looking forward to hearing the results of the fascinating work you guys are doing, Chris. In the interim, I don't suppose you want to tell us whether you're still recommending 25mm GP4Ks for your existing rims? :)
We do if they fit on your bike. Bike brands are starting to give us more room—3T being an excellent example—but many people still own bikes that limit the size of the tires they can use. So if they fit, then yes by all means use the 25mm version.
Take care,
Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling