Originally Posted by
Fat Boy
I have a bad wing, so Ive been on my rollers with a fork stand. It's Fredilicious, but better than no riding. Anyway....
With the fork held solid the frame flexes under you as you pedal, as we all know. The deflection appears to be primarily in the front triangle. As the frame flexes, it tilts the rear wheel slightly side to side. As this happens, the rear steers about an inch or 2 side to side. So when riding normally down the road this must be happening to some extent, which would contribute to tire scrub.
I've always said that frame stiffness doesn't affect efficiency. I'll still say that the frame itself is not 'absorbing' (I don't know what that means, honestly) power. I will say that this deflection may very well effect tire scrub which would affect overall efficiency.
Any thoughts?
What you're talking about, then, is the tire sliding side to side on the trainer's roller as you pedal.
On the road, theoretically, the rear tire would not only be propelling the bike forward, but it's also getting pushed side to side, which is the scrubbing you're describing. Then, the idea is that the sideways scrubbing contributes to the rear tire wearing down faster.
Am I reading you right so far?
The complication here is that the stationary trainer creates a pivot point at the rear axle that may not exist in regular riding. I'd suspect that, on the road, the whole bike pivots about the bottom of the wheels, at least as long as it's not getting flung around by heavy pedaling.
I also don't think that frame stiffness would affect sideways tire scrub enough to matter, either. Any frame should be stiff enough already.
We haven't started talking about
wheel stiffness yet, either.