Speedometer calibration

[bullard1255]

Can someone help me with the revs/mile for a 265/70/17? I am using the ford performance tuner and I entered 638 and it’s off by about 3 mph. According to hankook the exact tire I have is 657revs/mile

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[Dgc333]

If the manufacturer says the revs/mile is 657 that is what you should use.

Tire manufacturer to manufacturer will not be consistent for the dimensions for the same size tire so using their number is the best starting point.