Braking Fundamentals Question

[Tony_SS]

Would the same front disc brake setup have the same stopping ability on a 15" wheel vs a 17" wheel of the same weight and tire diameter? If so, why?

[Roadbuster]

Would the same front disc brake setup have the same stopping ability on a 15" wheel vs a 17" wheel of the same weight and tire diameter? If so, why?

I'll take a shot at this.

Theoretically all things being equal the only difference is the diameter of the wheel, I will make the assumption that the weight of the wheel moves outward. So where the weight is on the wheel changes, the total weight remains the same. That being the case and everything else equal, this will have a negative effect on braking. Concentrating the mass at the outer edge increases its rotational inertia making it harder to stop.

Jon

[Tony_SS]

Jon, that sounds right to me. I wasn't sure.

[silver69camaro]

I agree with Jon's theory, but I'll add more to it.

A given tire size for a larger diameter wheel, maintaining identical tire ODs, will have a larger contact patch and higher sidewall stiffness. The larger contact patch obviously will provide better braking, and the stiffer sidewalls will reduce the time between brake lockup and tire slip. This is splitting hairs, of course.

Another thing to look at is cooling. A 17" wheel will allow better cooling, which can be significant if you run hot pads.