I just put on a new set of Wrangler DuraTracs. They are 285/70/17 which is about 33" tire by the numbers but in reality are actually dead on 32"

My Jeep stock SRAs were 255/75/17 which is 32" by the numbers but in reality is only 31" or so.

When I asked the dealership to flash the computer to set them correctly I was told they couldn't because 285/70/17 is not a Jeep size and the computer wouldn't do it so they reflashed it to stock (and tried to charge me $50)

Now I can use my ProCalc to set the tires size to 32" (measured tires, not by the numbers) but shouldn't it already be correct since 255/70/17 is supposed to be 32"?

I hope that makes sense..

 

If your tires are exactly 32, then you shouldn't have to change anything. If you have a procal already however, there is nothing wrong with "doubling up". Plain and simple, I don't trust Stealerships.

 

You still need to do the procal to adjust if you want speedo to be accurate. tire size when off the vehicle are much different than mounted on the vehicle. measeure the size of the tire with the vehicles weight on it and then program it into the procal. the factory jk is set to around 31" because that is what the factory tires are with a load on them.