Tails

I guess you're lucky. I swapped the stock 225/75/16 tires for 255/85/16 Coopers. These are said to be 33", I don't know how big they are in reality. It sure is a much bigger step getting in!

Now, when I am going 60 MPH on the speedo it's 68 in reality (according to my Garmin Nuvi GPS). That's a little too much for me. The police are really looking for people speeding where I live, so I just ordered an AEV Procal from Northridge to correct the situation.

By the way, tire noise has increased quite a bit even though these are A/T tires, and mileage has gone down a lot (from 18 to 14 MPG). We'll see what the MPG indicator in the dash says after correction.

TCORUM

central texas but i'm also in the hill country and still its not that bad for me. last truck i had was a nissan frontier 4.0L nismo and it was balls to the wall with 33's. going into the JK i knew it had a lot less power but i also dont expect nor drive them to drive the same. i really think it comes down to driving style. if someone is heavy on the gas all the time they are going to think its a dog but if your not then you may think the power is fair. just a thought.

mpro26

I just put 305/65/17's on the jeep this weekend, so I need to get my GPS out and see how far off my speedo is now. I plan on going with different gears very soon, so I will be ordering the ProCal soon. Just from driving the jeep last night on I-95, the speedo doesnt seem to be off too much. Guess I will find out soon enough.

Hawnted

Do you change the shift points manually? Or is it calculated based on gear height?

If my speedo is correct does the ProCal do anything for me?

Adam3612

For what its worth when I put the 33" Duratracs on (275/70/18) then recalibrated something felt off, I measured them then tried again and it still feels off. I've used both a superchips and a procal to do this, even tried a different measurement. When I use my girlfriends Garmin Nuvi it shows im out 3 - 6 km/h, I trust the GPS because its been dead on in her car, my other car and every other vehicle its ever been used in.

Tails

Just an update for those interested.
I received my AEV Procal yesterday and programmed it to make my TPMS warning light and chime go away, and to calibrate the speedometer.
So I went from stock 225/75/16 tires to 255/85/16 Coopers. Without measuring them, I just assumed they woud be around 32.5", so I entered that on the Procal.

Tested today with my Garmin Nuvi GPS and the actual speed is one mile below what is indicated on the speedo. So when I see 60 MPH I'm going 59 and when I see 70 MPH I'm going 69. That's perfect for me.
Note that the Jeep doesn't feel any different. The AEV Procal isn't a tuning device.