speedo pinion gear selection

speedo is off about 5mph........... @35 it reads 40, @ 55mph it reads 61.

currently I have a 38 tooth pinion which is what Brewers chart shows for a 27" tall tire (275 / 60 / 15) with a 3:91. I verified it has 3.91's and installed the (blue) 38 tooth speedo pinion myself.

I'm thinking a 39 or 40 tooth speedo pinion. Can anyone take the guess work out of it for me?

Thanks,
Denny
Author: admin