Originally Posted by
Reynolds
I thought the number was precisely what mattered, if it's the same regardless of deformation.
No, the whole point if this thread was to establish that this isn't what matter. You didn't
add anything with this "drive by posting" because people already argued that point. You just reiterated what people were arguing was wrong.
Originally Posted by
mvnsnd
Thanks njkayaker.
This what I was trying to conclude earlier. The 'deformed' radius is what must be used for the radius calculation. Agreed that in a properly inflated tire, it may not be different from the unloaded tire radius.
No, it
will be different. The difference might be tiny (maybe, even hard to measure) but it
will be there! The other thing is that "properly inflated" doesn't mean much. There are a range of pressures that are "proper".
Originally Posted by
mvnsnd
It will most likely also be slightly different from tire manufacturer to tire manufacturer for the same size tire.
Doing the actual "rolling circumference" measurement accounts for all sorts of things that are otherwise hard to deal with. Note that manufacturers could supply the actual circumference of their tires (but doing the actual measurement still is going to be better).
Originally Posted by
Tulex
Do we all agree now that weight on a bike changes the roll out distance?
Yes, plus these important facts:
The "rolling circumference" (the standard term for this) is equal to pi*2*r, where r is the height of the center of the hub to the ground.
The "rolling circumference" is exactly the horizontal distance the center of the hub moves in a complete rotation of the wheel.
Originally Posted by
Reynolds
I just measured 2 rollouts, with and w/o load, there's about 2cm (1%) difference.
This is what the "theory" predicts.