Is it really necessary to recalibrate for a 295 70 17 tire, or would this be a waste of money? I have already reset the threshold on the tpm to run a lower pressure on the street. Will the calibration do anything other than make the speedo correct?

 

I would not waste the money. Head to the dealership and have them change the tire size to the max on their star scan. Your speedo will be real close (2mph) off and it is enough to accomplish what u need. If you go with a bigger tire I would get a Procal or superchips, etc. Spend the money on other mods!

 

Its a Rubicon, so the tire size is already maxed out. I kinda figured that it wouldnt make a difference.

 

I would, and I did. I have the exact same size. You'll get improved mpg's, shifts correctly and if you ever decide to go larger you'll already have it. Spending $150 for the procal was a great investment compared to paying the dealership to still have the speedo be incorrect then like I said if you ever change tire size you can adjust again for free.

 

Yes get the Procal. Never know if/when your gonna regear, get bigger tires, want a lower TPMS setting and so on.

 

Procal def worth it for me. I had the dinky 235's stock sport tires/wheels so it was a must for me to buy the procal. I get 22mpg+ on highway running 285/70/17's Nitto Terra Grapplers and 2.5" lift (actual mpg's calculated, not just the dash mpg indicator). It adjusts speed and shift points, not to mention you can program one-touch lane turning signal and turn TPMS to 0 psi.
Since I bought aftermarket wheels and didn't want to pay for stupid TPMS to babysit my tire pressure (which cost more than a procal) it was a no-brainer for me. Look in the 'for sale' forum on here- you can pick one up for $80-$100. Just make sure they reset it to factory before sending it to you.

 

Can you really buy a used one?
I read somewhere that it locks up with
Your VIN number and can only be used with one vehicle.

 

You can get a used one but the previous owner needs to program the restore to factory setting iot get the procal unlocked from that vehicles vin. I think that's what I read in my manual. I got 295/70-17s and got the procal just so I could have peace of mind that everything I paid for in my new jeep worked correctly. Ie speedo, mpg gauge, odometer. Yeah, it's still new and still has the new car smell, why wouldn't you invest 150 so your tires that cost a grand or more will work properly with your 34+ thousand dollar jeep?

I checked my adjustments with a gps and found 32.25 got me accurate on the speedo. Mpg went from 11-12 mpg before adjustment up to 15-17 after. The odometer/ trip reads properly for miles remaining in the tank and actual distance traveled. Turned on the fog light daytime running lamps and saved a couple bucks on car insurance.

 

Side note on tpms, I set mine at 26 for daily use and adjust to 19 for offroad. The procal is fast and easy enough to just make the change taking seriously about a minute or less. I know a lot of people find the Tpm system annoying but I think it's a great safety feature that helps keep me informed and my kids a little safer on and off road. You don't always hear a tire getting punctured.

 

FWIW I have a 2012 JKUR and just went to 285/75R16" Duratrac tires my speedo was right on when compared to the 430N Garmin nav. I also checked the odometer against mile markers and it was right on. So although I bought a Procal I only used it to set the TPMS to zero since I am not running sensors. It worked great for that