Doc
Full Access Member
Forgot to ask about this in the previos thread.
My truck came with 235/85/R16 tires and a 4.10 rear differential. I changed the tire to 285/75/R16s and the differential to a 3.55. When I checked my speedo calibration after the changes it was right on the money. I tested it by driving 5 miles at 70mhp, 5 miles at 65mph, and 5 miles at 60mph. I timed the distance with a stop watch and came up with these results:
5 miles @ 70 was actually 69.98mph; 65 was actually 64.90mph, and 60 was actually 60.11mph.
I thought I would need to have the speedo machine calibrated. Does the computer do it automatically. It just seems weird to me that I didn't need to make any changes after adding over 1 inch to the tire height and changed the rotation in the rearend.
My truck came with 235/85/R16 tires and a 4.10 rear differential. I changed the tire to 285/75/R16s and the differential to a 3.55. When I checked my speedo calibration after the changes it was right on the money. I tested it by driving 5 miles at 70mhp, 5 miles at 65mph, and 5 miles at 60mph. I timed the distance with a stop watch and came up with these results:
5 miles @ 70 was actually 69.98mph; 65 was actually 64.90mph, and 60 was actually 60.11mph.
I thought I would need to have the speedo machine calibrated. Does the computer do it automatically. It just seems weird to me that I didn't need to make any changes after adding over 1 inch to the tire height and changed the rotation in the rearend.