I was thinking of going with a smaller tire diameter from stock to 215/50/15. I read the stickies and it said not to go up or down more the 3% but Im not to worried about that. How much of a benefit would I see in acceleration?

 

Not much at all. You would need to really come down in size for it to be really effective.

 

This size has a tire diameter of 600mm vs 650mm standard. So about 8-9% increase in torque at the tire patch.