Wheel and Tire Change: Recal Needed?

Firemandiver · November 18, 2017

Hi,

I am new to the forum. Already finding little bits of helpful info. I'm sure I'm just not looking in the right place, but I can't find what I'm looking for, so I figured I'd post:

I just swapped my stock 17s for stock 20s. No other changes, just stock for stock. The new tires are a little taller overall than the old ones. Am I gonna need to do a speed sensor recalibration, or will it just change my speedometer reading a bit?

Anyone been through this already?

Thanks, FD

Armo325 · November 18, 2017

I doubt the size difference will make much of a difference and I don't even know how accurate GM is when they calibrate their speedometers. They might use an "average" speed for their various tire sizes. Someone smarter than me on the software in the truck could probably answer that.

If you want to know how your speedometer will change, you can take the old and new tire sizes and put them in to a calculator online. There are several to choose from. Here's one I just grabbed from Google:

https://tiresize.com/speedometer-calibration/

Firemandiver · November 18, 2017

Thanks for the info and quick reply. Like you, I was thinking it wouldn't be a big deal, but with all the new technology that's in these trucks.....you never know for sure. I haven't even driven it yet. Just put the new wheels on this morning. Will update when I drive it later today.

Thanks, FD

Firemandiver · November 19, 2017

Well, all okay but.....

The tire/wheel change didn't seem to be a problem. I could feel a difference in the way the truck drove, though. Seemed to be a little firmer with a little more resistance when turning. Nothing bad, but noticibly different. Stands to reason...the new tires and wheels are wider.

Big surprise was the TPMS. I got almost brand new wheels, complete with sensors so it was a quick change without having to swap out sensors. I've ordered a TPMS tool, but it won't be here til next week. Thinking I'd be slick, and not have to ride around with the TPMS light on until my trigger tool arrives, I threw the original wheels and tires in the bed. I figured it would keep the system happy until I can pair the new sensors. It didn't. About twenty minutes into my drive today, the light came on. Apparently, there must be an inertia sensor built into the TPMS sensor. I guess the sensor not only has to be near enough to transmit, but also in motion to work.

Does anyone know for sure?

Thanks, FD

BTW The tire size calculator said 1.62 mph difference in 17's vs 20's

Armo325 · November 19, 2017

8 hours ago, Firemandiver said:

BTW The tire size calculator said 1.62 mph difference in 17's vs 20's

This is speculation but I'd bet that within the margin of error for the speedometer.

I'm not smart enough on TPMS to know what is causing your current issue but it's interesting, for sure. I suspect you'll be good to go once the tool arrives and you can reprogram everything.

swathdiver · November 19, 2017

10 hours ago, Firemandiver said:

Apparently, there must be an inertia sensor built into the TPMS sensor. I guess the sensor not only has to be near enough to transmit, but also in motion to work.

Does anyone know for sure?

That's the way it works on the older trucks. The dealer should be able to reprogram your computer for your new tire size, type and pressure.

Of course you're going to lose ride quality when going to a taller wheel with a shorter sidewall.