[**grumpy**]

If I remember correctly, gear ratios are based off a 27" tall tire, so at 27" a 3.08 is a 3.08
at 29-30" tall tire, the gear equates to a 290-ish
Just as with a 25" tall tire, the gear jumps to a 320-ish gear.

My tires were 255-70s or 265-70s, cant remember, but big.