I just had the original 31 tooth (green) speedo pinion changed out for a 30 tooth (yellow) speedo pinion since I've gone to 235/75-15 tires, but the speedometer reading is still off a little (I asked a motorcycle cop to pace me when I was waiting for a light, and when he called out 30mph my speedo read 37-ish).

I the shop that installed it for me that the retainer indexing be set with the middle mark line up with the mark on the housing, and I wonder if changing it will help with that or not.

Am I going to have to find a 29 tooth speedo pinion gear?