Just came back from the dealer and was told, they can't load a new tire size because they didn't have a option on their computer". He said that he's loaded other tire sizes on a 2007, but the 2008 is different.

My Jeep came with 245/75/R16's and i want the 255/75/R17 size loaded because it's close to my current size 285/70/R17.

Anyone had this same problem?

They did however change my TPMS pressure for free.
Free doesn't happen that often at a dealership.

BTW the tech also thought the speedo would cal itself after a few miles. I told him that was BS. I guess he thought it was magic or something.

 

I've read lots of different answers from different folks here on JK-Forum. Some say their dealer calibrated only to 32" tires (max JK size stock), others say they're dealer couldn't go larger than 32. My dealer told me he wouldn't know until he connected up the computer how large he could go--and even though he was going to have to connect up that computer for the safety recall, he wanted $90 to recal the tires, even if he couldn't go to 33 (which is what I'm running).

I decided to skip the dealer and buy a Hypertech, which allows recalibration up into the 40s. It does other things as well. Price was $380, though I hear Northridge4x4 is having a sale for $360. There is also the Accupro, which does little more than recal the tires, but it costs only about $180.

 

Its not possible.
Gears have no effect on the speedo in the JK, because it uses wheel sensors to figure out how fast the Jeep is going. Only tires will effect the speedo, or recalibrating the speedo itself via programmer.

 

Thanks for all the responses. I think i might eventually go with the Hypertech whenever the money is availible.

I think $360 is quite a bit and it makes me worried about the warranty issues from reflashing the computer. I have heard the dealer can check for the last reflash if you have a problem. That's one of those buddy knew a guy who had a brother in law that had this problem before kind of thoughts.

 

Can someone give me, or PM the name of a dealership who's done the tire size change on thier Jeep? I am trying to get the 255/75/r17 size loaded instead of the 245/75/r16 mine came with. I just wanted to call your dealer and ask them how they did it so i can help my local dealer figure it out.

 

Sorry I can't be of more help with your speedometer question, but I am curious about your TPMS change the dealer made for you. How did they change it and what did they change it to? Did they lower the pressure on the sensors? If so what did they lower it to?

Thanks

 

the biggiest mine could go up is 245/75/16 and i run 285/75/16


I am thinking about getting the accupro

 

They lowered the sensor range from 35psi to 28psi. The tech just hooked it up to their plug-in computer and punched buttons. All i told them was i wanted to run 28-30 psi instead of 35. He said i was good to about 26psi after the cal. With the thick sidewalls on the KM2's i could probably run 26 psi without a problem, but i'm going to stick with 30 psi for now.

Yeah, i might just get the accupro, but i think i can handle the 32" stock size for the price difference. Someone has to be able to reset it. What do they do when they add the XS option at the factory. I guarantee all the computers are the same, they just update for the package ie. XB, XS, Sahara, Rubicon.

 

I have not confirmed this, but I'm pretty sure that the JK has the Hall Effect Speed Sensor where the gears, rather than the tire's tone ring sensor for ABS, etc. would impact the speedo accuracy.

So changing the tire speed would impact the speedometer accuracy, but so would changing the gearing.