I've had to do this math several times, but for the life of me I can't remember the equation. I have two bridge saws that run 13-16" blades and I have to calculate blade speed vs. arbor speed for certain materials/types of blades. I usually call my cousin, a physics major.
the same reason you should stick with manufacturer recommended tire and wheel sizes, unless you can reprogram for different sizes. Wheel speed is read at the hub, and it can throw your speedometer off quite a bit.