HOW TO RECALIBRATE THE SPEEDOMETER ON 92-96 FORD F-SERIES AND BRONCO .: Articles
OK, before I go through a lot of trial and error. Why would it matter if have 15" or 16" wheels when resetting the speedo calibration? I have the revs per mile figure from the tire manf.Thanks for any info.

 

There are several misleading PSOM calibration articles that reference the 15 vs. 16 inch rim/tire size. All of these articles never explain why.....If you have a 8.8" rear axle (f150/Bronco) then use the .0135 conversion factor. If you have a Sterling 10.25" rear axle (F250/F350...implies 16 inch tire/rim) then use the .15 conversion factor. The tire/rim size (15 vs. 16 in.) has not real bearing on using either conversion factor per se, it's the difference in tone ring teeth between the 8.8" and 10.25" rear axles. The 8.8" uses a 108 tooth tone ring, the Sterling 10.25 uses a 120 tooth tone ring. Thus the difference in conversion factors.

If you have a F150/Bronco with 16 inch tires/rims use the .0135 conversion factor.

 

It's an F250 w/ the sterling 10.25. This is good info.