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I put 245/75/R16 tires on a 2002 Sport Trac. I have a programmer, the software for it has a selection of sizes and a calculator where anything (I assume whole numbers only) can be entered for width, sidewall height and wheel diameter.

The rev/mile it has for 245/75/R16 is not right. I measured a 94.75" circumference on the tires, which is 668.7 revs/mile. The lowest default setting available is 679.

The speedometer reads about 2 to 3 MPH too fast, compared to DigiHUD on my phone.

What nonexistent tire dimensions can I enter to make it come up with 669 revs/mile?

I've tried at various sites with size calculators but they all only allow inputs for sizes that are actually made and none of them allow inputting a circumference to get tire sizes that match. In all cases I can only come up with real nominal sizes that would be 10 or more revs/mile over or under what the tires I have really roll.

So I want to fake it to force the @#@#% computer module to run the speedometer correctly.
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