I'm certainly not saying that all clinchers have lower crr than all tubulars period. In my case I usually run Veloflex Carbons (crr around 0.0049), which I have accepted as being worse than many top end clincher tires out there (e.g. GP4000s II). My point was that it's not actually all that much worse, and I can live with the drawbacks given the benefits.sungod wrote:why?
simply because it's become fashionable for people to parrot that clinchers have lower crr than tubs does not mean any given clincher has better (or worse) crr than any given tub
if you use the bicycle rolling resistance website data as a reference, the two lowest crr results are clinchers running tubeless, then it's a tub, if the clinchers were run with a normal inner tube i believe the tub would have lowest crr
data (for running tubeless) from brr site...
Vittoria Corsa Speed (open TLR) 7.7 W
Continental Grand Prix 5000 TL 8.3 W
Vittoria Corsa Speed (tubular) 9.1 W
note: these 'wattages' need understanding in the context of brr's methodology as explained on their site, safest is to regard them as relative values, not real world figures
looking deeper, the conti is 27mm wide and quoted loss is at 120psi, the tub is 23mm wise, same pressure
you might run a 23mm tub at 120psi, will you really run a 27mm clincher at that pressure? at 100psi the clincher loses 8.9w, at 80psi it's 9.9w, oh dear, and that's still without an inner tube, so which is 'faster' in the real world?
the brr methodology may or may not translate to equivalent results on the road, but taking the headline numbers to say x is 'better' than y clearly is unsafe
reality is that there are many variables and trying to test them all would be uneconomic - for instance do the results stand irrespective of rim width? road surface? temperature? pressure? rider weight? what about non-linear effects?
at road speeds, i'd think the crr losses have the potential to be dwarfed by aerodynamic impact of tyre/rim matching, especially on the front
The bigger question is whether I'm being penalized significantly more on the aerodynamics of the tire tread and tire/rim interface compared to running clinchers, which I think is the same question you're raising.