Alright heres a question for you guys. Say I find a gear ration I'm really happy with, and I go to replace the spur, if it's the same number of teeth but a different diameter, am I going to notice a difference and if so which would be better, the smaller or bigger diameter? Thanks.

if the diameter is different, the tooth count has to change.. thats why some are bigger and some smaller. more or less teeth..

if you want to get the same ratio. take your old spur tothe count , and divied it by the pinion toth count.. write down that number.. then if you get a larger or smaller one do the same thing.. the number will change.. just keep dividing different pinion sizes until it gets close enough to wear it was..

If you are going from 64 pitch spur to 48 pitch spur the number of teeth could be the same but the diameter will change, and so will the ratio.
A 96 tooth 64 pitch spur will be smaller than a 96 tooth 48 pitch spur.
You will have to do the math to get back to your desired gear ratio.

Spur/pinion=ratio
96tooth spur/30tooth pinion=3.2 ratio
If you want the same 3.2 ratio with a different pitch use the above math to find the proper pinion to run.

If this helps cool.
If it is in no way related to your question, sorry to waste your time.