Pats fan

I just ordered a procal for my jku and was wondering what you guys set the procal at for speedometer correction with the Goodyear Wrangler DuraTrac 315/70/17?

BRinSCupstate

I put a piece of tape on side of tire and a piece on driveway, made a mark on tapes to line up, rolled the jeep back 1 full tire revolution, measured distance, and divided that by 3.14.

jadmt

Aev says to park on flat level surface and measure front tire from bottom to center of hub and times that by 2. This is directly from the inventor of the procal.

12mile

Aev says to park on flat level surface and measure front tire from bottom to center of hub and times that by 2. This is directly from the inventor of the procal.

This is exactly what I did.
Procal instructions exactly

jedg

So there's a thread on this where I used all three methods...

1. Measure from center of hub to ground X 2

2. Roll tire one revolution and measure distance / 3.14

3. Measure tire from top to ground (using a level)

All three came out to within 1/4" of each other, that was conducting each measurement 3 times.

SO... pick your poison, they all work sufficiently.

Old Syko

No matter how I measured mine the speedo and odometer weren't exactly right when compared to my hand held gps that has proven to be accurate in other applications. My DuraTracs when mounted on 17x9s show a stand height when measured with a level from top to the ground of 34 1/4". When measured as AEV suggests there is less than 1/4" difference. In order to get proper readings that are dead on with my gps I had to set the Procal to 33 1/4. I've learned since that a number of folks have found the same thing. Good luck with yours.

Pats fan

My tool box is in my storage locker so I couldn't get to my tape measure or level (I live in a small apartment) so i took a flyer and set it at 33.5 and according to the GPS at 70 mph the speedometer is at 69mph. So I think that should be good enough?

BFGMallTerrains

I have the exact same setup of tires and wheels, 33.5 setting gets me within 1mph of my GPS

Jeepstin12

Do the method the guys mention above. I did the AEV recommendation and it was off. I did the measurement, and got me within 1mph. I'm spot on under 60 mph. Above 60, I'm over by 1mph.