Changing Wheel/Tire Size

[bigman32hockey]

I own a 2020 Silverado 2500 LTZ.  I have the optional chrome wheels on the truck and 275/65R20 tires.  A friend of mine recently purchased new wheels and tires for his 2020 Sierra 2500 AT4.  I've been wanting to put some black wheels on my truck for a while now.  He gave me the wheels and tires for my truck.  Can't beat THAT price!  I do have a couple of questions though.  First, will going from 275/65R20 tires to 275/70R18 cause me any major issues?  I've calculated the total diameter difference to be 0.9 inches.  Anyone know if the speedometer and/or odometer will be totally off because of this?  Secondly, does Chevrolet sells replacement plastic center caps that would fit a GMC wheel?  It's pretty blacked out, but I'd rather not have a GMC logo on a Chevy truck.  Just looks kinda weird in my opinion.  Any help is greatly appreciated.  Thanks. 

[kylant]

you are going to an inch smaller tire. the speedometer will read faster. 

on my truck, and others I have heard of, the speedometer calibration for the 275/65-20s is fast already. 

I put a 295/65-20 (1" taller) tire on my truck and now my speedometer is dead accurate with GPS and roadside radar.

 

as far as the cap, depends on the wheel. but i know gm makes black caps in both the GMC and Chevy flavors for certain wheels. I have seen guys swap caps and do exactly what you want to do

Edited April 30, 2021 by kylant

[Westy5]

I swapped my stock 275/75r17 tires for new wheels and 295/70r18 tires,which are quite a bit bigger, on my new 2022 2500 hd . And at 75mph on the Speedo gps says I’m going 78 mph. I’d assume that the faster your going a little more it would be off

[Another JR]

Using the mile markers of a marked 5 mile highway speedometer test section, my 2021 3500hd with stock Michelin 18s seems to be almost dead on accurate. At 5 miles the number flipped about 100 feet after the marker. That’s just under 1/2% error. 
 

I have not been able to find out if there is a different calibration on trucks delivered with 20 inch wheels. 

[redwngr]

https://tiresize.com/comparison/

 

above that 60 indicated will be 58.4 actual  

 

58.4/60 = 97.3% of current speedo reading.

 

[goforit]

Sorry to revive an old thread but I didn't find anything more recent and on topic.

 

I recently swapped my stock 17" LT wheels for a takeoff set of 20" LTZ wheels.  I purchased them from a place that deals in takeoff stock wheels for a variety of makes.  I had the TPMS programmed at the time, and I assumed I could have a dealer change/correct the tire size to another stock size, 2 dealers I called said they can't do this on the current generation trucks.

 

Since I installed the 20" set I have been using a gps speed app on my phone part of the time I am driving and some of the time the speed is correct and some of the time it is off nearly 10% which is what I expected, as in one day it might match the app dead on and the next day I am going 10% faster than it reads.  What is everyone doing to correct this or at least have it be consistent?

[Another JR]

I recall in another thread someone mentioned that there is a different software setting for the different optional tire sizes to make the speedometer accurate. You are going from one factory size to another factory size. I’d suggest asking the dealer if it is something they can reset for you for not too much money. 

[goforit]

I contacted 2 dealers today and both said that they can’t change the tire size even though I am trying to go from one stock size to another, so I was wondering if anyone had the same experience.   I can buy an aftermarket module to perform the calibration/adjustment, but I thought I had read that the dealer can change it to another stock size so I wanted to prevent adding hardware if possible.  

[Poopster]

I just changed my wheels and tires on my 2022 GMC AT4. I went from the OEM 20” wheels with Goodyear Territory MT LT265/60R20 to Toyo Open Country A/T III 35x12.5R17LT. The dealer said no can do for relearning the TPMS on a aftermarket tire. I purchased the tires & wheels from Custom Offsets, and they said the TPMS should relearn themselves after around 250 miles which hasn’t happened yet.

[DuckBoi]

On 5/25/2023 at 2:36 PM, Poopster said:

I just changed my wheels and tires on my 2022 GMC AT4. I went from the OEM 20” wheels with Goodyear Territory MT LT265/60R20 to Toyo Open Country A/T III 35x12.5R17LT. The dealer said no can do for relearning the TPMS on a aftermarket tire. I purchased the tires & wheels from Custom Offsets, and they said the TPMS should relearn themselves after around 250 miles which hasn’t happened yet.

How do you like the toyo at3's?

[Dr1ft3r]

Changing tire sizes is a common thing to do. I seen it in racing a lot. There are plenty of aftermarket shops that have the ability to correct your speedometer. It doesn't have to be done at the dealer. In fact, I think it's illegal for the factory to lock out the ability to have the speedometer calibrated since it's a Federal law that a speedometer must be accurate within 5 mph at a speed of 50 mph and there's no law preventing someone from changing their tire size.

If the dealers don't want to make some money for a simple adjustment, spend your money somewhere else.

[Poopster]

On 5/26/2023 at 9:08 PM, DuckBoi said:

How do you like the toyo at3's?

Best tires I've ever owned. I've had BFG, Goodyear, just to name a few.