Speedometer correction for larger tires
 

Stock tire size on my HF is 165/70R13 (22.09")
Current tire size on my HF is 175/70R13 (22.65")
I'm planning to move up to a 15" rim with one of these tire sizes:
195/60R15 (24.21")
205/60R15 (24.69")

I need to know the stock HF transmission gear ratios, and the differential gear ratio to figure out the percentage of difference the larger tire will make. Then, I need to know if there is a way of correcting for this at the Speedometer.

Formula for determining speed difference caused by tire size change:

MPH = (Engine RPM x Tire Diameter (in inches) x 0.003 ) divided by
(Transmission Gear Ratio x Final Drive Ratio)

Example: RPM x tire x constant) / (5th gear x stock diffs)
(3000RPM x 29.75 x 0.003) / (0.85 x 4.11) = 76.6 MPH

The tire diameter must be measure carefully, as it will impact the
formula greatly. What you can see is that everything is directly
proportional. That is, a change in tire diameter from 28 inches
to 31 inches, (31-28) / 28 = 10.7% will impact speed by 10.7%.
And likewise, a diff gear change from 4.11 to 4.88,
(4.88-4.11) / 4.11 = 18.7% will affect speed by the same amount.