Installed an AEV Procal. Running 35" Trail grapplers. My speedo is still 5 mph off according to my gps. WTH?

 

Tires measure 34" with 35 psi. According to Procal, 34-24 = 10, and that is the number to put in. It's not working

 

An easy and accurate way to measure tire diameter:
Stick a piece of chalk in the tread.
Move the Jeep until there are two chalk marks on the pavement.
Measure between the chalk marks.
Divide the measurement by 3.1416.
That's your tire diameter.
It removes the variables encountered with other methods.

Assuming your tire was 34", did you enter 10.00, or just 10?

 

I put in 10.00

 

Did your horn honk twice after you connected the ProCal? Also remember to round up, if it's not an even 1/4 inch.

Is your Jeep a 2 door? If so can you post some pictures? I really wanted a True Blue Freedom Edition, but couldn't find one equipped the way I wanted around here.

 

Yes. Horn honked twice

 

Why don't you try going .25 lower and set the Procal to 9.75 and compare that to your GPS and if it's still off, start adjusting the size in 1/4 increments...

 

exactly how I got mine running accurate.

 

Thanks. I'll try that tonight

 

i had to play with min a little too until i got it perfect. i used both my gps with speed display and those "SLOW DOWN" signs that tell you how fast you're driving to get my speedo on point.