i have 33 nitto terra grapplers,i measured they seem to be exactly 33,so i punched it into the pro cal,but im worried if its a tiny bit off either smaller or bigger,it may put more miles on my jeep,i dont want to run up the miles on it,will this be an issue,the transmission is running way better since i recalibrated with procal,alot faster and more power,any suggestions would be great, thanks

 

You'll be fine. If you want to be anal you can check your tire height every six months and adjust accordingly. You would have to be way off to really cause an issue.

 

If you have a GPS you can check your speedometer against the MPH on the GPS. This will give you an idea if you have adjusted correctly with the Procal. I tweaked mine after checking against the GPS. I did discover that you have reset to stock before you readjust the tire size. You cannot just "add another quarter inch". Reset to stock and then start over with the tire settings. It worked great. I agree-- the calibration really improved the performance of the JK by getting the shift points right.

 

It says in the manual to round to the closest 1/4". I programmed mine at 34" with my setup and checked it with an iphone app and it is within 1 mile per hour. Figured it is close enough.

 

I have never reset my procal to stock before changing size-I changed size until it matched GPS.

 

I have just put 35's on my JK and dont know how to adjust my speedometer. it seems to be about 10 km out when i compare it to the GPS.


Can someone tell me how to adjust it??

 

You need a programmer such as a procal and a tape measure.

 

A 33 that measures 33"? Riigghhttt.......

My 33.27" Terra's (mfg's listed height) measured out at 32" even (16x8.5" rim, 32psi, normal load on my JK). Curious how you measured them.

If you don't have access to a GPS, (which may be a few mph's off anyway) drive around and find one of those radar signs they put out from time to time to tell you to slow down. From my experience, the ProCal was pretty much right on with both my 295/75/16's and my 315/75/16's. (the flashpaq, on the other hand, doesn't seem to be nearly as precise.)