Quote:
Originally Posted by marciero
As I've said, I've found your experience compelling. But I am dubious of claims like this because the difference of 2mm is likely to be small. You say "measured", so is this based on times over a given course with both tires rather than a math model for power using rolling resistance and aero coeff?
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Chung method. Multiple measurements. Same kit, same power meter, on the same days.
If a rim is say 24 mm wide and you put a 25 mm that balloons to 26 mm, this is not going to be trivial at speed. At 15-20 mph, 2 mm is trivial.
You can search for wind tunnel results if you don't believe me. I do not know if the Pros carefully match tires to front rims, but I suspect they do and I would not be surprised to see 22 or 23 mm tires on the front wheel for time trials. My fastest front tire is a 22 mm Supersonic, it is much faster than a 25 mm GP5000 at 45-50 km/h
Edit:
Here is some testing done by Tom A. from at the Specialized wind tunnel. A 22 mm tire vs 26mm vs 28 mm on the same rim changed the Cda by 0.0015 and 0.0025 m^2, respectively. At 45 km/h, the 28 mm tire would take an additional 30 watts approx. vs the 22 mm front tired wheel. I did not see that big of an effect on my wheels....more in line with the following. Two other places to look would be Hambini and his friends at Flo. Both claim to have done wind tunnel tests and both have published comparisons of different width of tires. At 20 mph, an
improper fit costs 2-4 watts per both Hambini and flo and 10-15 watts at 30 mph per Hambini (Flo only shows results at lower speeds).
http://bikeblather.blogspot.com/2016/