Your speedometer will read about 7% slower than what you're actually going.
Total height of 245-75 tires = 245 * 75%=183.75
Total height of 235-85 tires = 235 * 85%=199.75
Taller tires have a larger circumference. Larger circumference means more distance traveled per revolution.
If you take it to a speedometer or driveline shop, they can recalibrate the speedo.
Thursday, January 5th, 2012 AT 4:41 AM