Originally Posted by
guadzilla
On a different note, since we are talking CRR, here is an interesting article:
https://blog.silca.cc/part-4b-rollin...-and-impedance
It shows the difference between the theory of drum tests vs actual riding on the road (where what they call "impedance" also starts to play a role). There are a couple of interesting take-aways that I see here:
1) It is better to err on the side of tire pressure being a bit too low vs a bit too high
2) Tires with more supple casings tend to have lower CRR and also more forgiving of over/under pressure
Does that level the playing field in the rear world, for tires like Turbo Cottons, which test 2-3W slower than GP5ks in the drum test but have a much more supple casing?
Wouldn't this be dependent on the road surface and sprung weight? As shown in the article linked, rolling resistance/friction increases with surface roughness. If friction is a function of the area of the contact patch, as well as the per-watt flex of the sidewalls, then on a perfectly flat surface, the best tire would be completely stiff. As surface roughness increases, the tire would be spending less and less time in contact with the ground, due to bouncing, leading to a pedaling inefficiency.
For a straight line path then, the ideal (efficiency-wise) tire would then be a combination of the minimum surface area for "good" traction with the minimum amount of deformation necessary to maintain that surface area.
It's conceivable then to me, that the Turbo Cotton tires would outperform the GP5k in certain surface roughness conditions.