Hey hey everyone,
So I put some 31x10.5x31 on the D and now the speedo is off about 6-7 miles per hour. Any one know how to calibrate it for the new tire size???
Thanks Gents

 

You can get a tuner like a www.superchips.com or www.hypertech.com

 

Okay, which do you like better..Superchips or the Hypertech? I see Facory has a hypertech for sale...HMMMMM

 

FIRST, I will assume you have a type in your post with 31x10.5x31 as your tire size. That is impossible.

So... assuming something like 31x10.5x15... that was/is my stock size.

If you are off 6-7MPH, it is not just your tire size. What did you have on there before, training wheels?

IndyD

 

Hey Indy, I have 275/75R/16's on my wife's 2003 Durango with the 4.7 in it. Stock is 245/75R/16's. Do I have to reprogram my PCM because it is off by 3-4mph? Or is there an easier way without buying expensive tuners besides going back to stock.

 

If I may interject. I think the 275 is the tire width. I don't think it has anything to do with the speedo being off.

 

Width is the 75R, tire height is the metric numbers in front like the 245 versus 275. A 65R will be wider and also a 55R is wider.

 

You can have the dealer reprogram for the tire change I think. Also, some higher end tire shops can do it. In the end however, most don't like to mess with the computer programming and will leave it to you. Thus, IIRC... the only method is your own tuner to tweek it. I don't think I have ever heard of a method you can do to the D to make it understand it has different sized tires. You most certainly will need a programmer.

Or live with it.

IndyD

 

I beg to differ, my friend. The 275 is the width of the tire from sidewall to sidewall. BUT it DOES affect the circumference of the tire. You had 245/75s as OEM. That meant you had 75% of 245 milimeters as the height of the tire from rim to tread. So if you installed 275/75 then you increased the height from stock.

 

So the height is taller and that is why the speedo is off 3-4mph right?