Speedometer Difference

[HarrySanders]

I just re-tired! I went from the Steeltex 245/75R16's to Michelin LTX M/S in 285/75/16. I'm curious how far off my speedo now is at highway speed. I would think roughly 5mph?

Am I in the ball park?

[AlanL]

Use an on-line tire size calculator (use your favorite search engine to find one) to get the percentage difference.

The amount the speedo is off will vary with teh speed itself. I think that I remember someone saying that going from 245 to 285 tires will be about 8%. (65 on the speedo, will register at 59.8 for instance).

[norskeman]

I went to 265's

see this link for info:

http://www.miata.net/garage/tirecalc.html

2004 GMC 2500HD Ext. Cab, Long Box ,Duramax (LB7)/Allison; GMC bed liner;Air Lift Super Duty air bags; Michelin LT265/75-R16 LTX M/S ; Luverne Running boards; Bilstein shocks; Delvac 1300; Isspro gauges; Racor frame mount fuel pre-filter; Transynd transmission fluid.

[More Power]

The folks at http://www.superlift.com/speedo.htm offer a Tru-Speed vehicle speed calibrator that can be used to get the speedo/odo re-calibrated.

MP