Gearing ratio spur to pinion
 

Guys if dropping a tooth or two on the spur how many teeth do you go up on the pinion .

Say i go from 74t spur / 24t pinion and drop to a 72t spur .There must be a baseline tooth count ratio for every tooth changed on a spur to pinion?

spur# / pinion# = your reduction at that gear set
74/24=3.083
72/23.354=3.083
23t pinion would result in a little less top speed and a 24t would give you a little more than your original set up. BrianG's calculator is a very useful tool for figuring out all your gearing and speed requirements