Wheels Off Road

GMC question. 2007 Sierra Crewcab 4x4 What changes if you change the original wheels with larger wheels.?

GMC 20 inch wheels with 275/55SR20 Goodyear Eagle LS-2 tires transfered from 2007 Sierra 1500 Crewcab 4x4 with SLT trailering package with 3.73 rear end, to a 2007 GMC Sierra 1500 crewcab 4x4 with Max trailering package that had 17 inch wheels with Bridgestone Dueler A/T on off road P265/70SR17 tires on it. These tires are original factory installed equipment on respective trucks. Are there suspension differiences which would not allow the swap ? Will it change the towing capacity ? Can the on board computer be programed for the wheel swap ? The GMC answer is generic and noncommital.

Public Comments

1. The only major change is that the speedometer will have to be re-calibrated to account for the new tire size.. this is important because all of your scheduled maintenance depends on accurate odometer readings.. (3" in diameter is a big difference) it would suck to accidentally nullify a warranty by altering the true reading. I don't think anything else will change dramatically with suspension and towing.. might want to consider a breaking system with a little more stopping power.. probably just pads and rotors .. if you put $800 into new tires.. another $150 for brakes is a minor sacrifice. I put larger tires (same type - larger size) on my Dakota a few years ago.. I didn't notice anything special or different after the switch worth mentioning.. seems a little less stable in heavy snow and a little more road noise.. that is about it.
2. Yes, you will have to get your computer recalibrated for this change. See your dealer & ask for anything else that may need changing.
3. yes the computer can be reprogrammed to take into account the larger tire diameter.also the shift points in the transmission will have to be altered,since the tires are 3" taller than "factory" it changes what was once constant in the computers program.once the new constants are entered the computer will be fine. it mostly affects speedometer/odometer, and rpm which is used in determining what gear the transmission should be in.
4. Hmmm... 275/55-20 vs. 265/70-17 - is there a difference in outside tire diameter? If not, you might be able to get away without recalibrating the computer. But you will have to relearn the tire pressure sensor posittions. I think any towing capacity change would be minimal.
5. If putting larger tires on your vehicle you will thow off your speedometer, you won't have as much of a space between the wheel wells and tires which can cause some rubbing on the wheel wells if you hit a bump excessivly. As far as towing capacity its not going to affect that, just need a drop hitch to level out your trailer. The computer can be programmed for power, and depending on the system the electronics for the speedometer might be able to be reprogrammed also.