what does it take to recalibrate the speedometer to be able to use 20"wheels?

Gilligan · #1 (**permalink**) 11-05-2009, 10:08 PM

the vehicle is an 08 dodge with 17" wheels on it already. Wondering what kind of trouble it will be to get the speedometer to work correctly .

Dave · #2 (**permalink**) 11-05-2009, 10:08 PM

The wheel size doesn't matter. It's the overall tire diameter that does. As said above with larger wheels you will run low profile tires so the overall diameter should be close. You can check it with a tape measure and if the new tire/wheel combo is noticeably larger your dealer can adjust the pinion factor with a scan tool to correct the speedometer and transmission shift points.
Be sure to have this done if there is any significant difference in diameter as it will affect the shifting on an automatic if you don't and can actually damage your transmission over time.
Hope this helps.