New tire size speedometer calibration issue

RushTheBus_ · October 13, 2022

I have a 2019 silverado 1500 RST with 265/65/18 tires that I just upgraded to 275/65/18 (stock trail boss size). I want to get the speedometer adjusted to this tire size for piece of mind with odometer/speed/fuel econ. I spoke to someone at my local dealership a while back and they said they have to order a GM part that is ~$150 for that specific tire size to reflash the ECM. I called back today to get this done and they acted like they have no idea what I'm talking about. I am not interested in getting a chip to possibly void my warranty. Does anyone have any knowledge on what exactly I need?

Edited October 13, 2022 by RushTheBus_

Transient · October 13, 2022

First, a chip won't void warranty unless the chip is the cause of a failure or problem. A warranty can't be voided for aftermarket products installed, just not honored due to breach of warranty. This is federal law titled Magnuson-Moss Warranty Act.

Secondly, dealerships can recalibrate speedometer and computer for other size tires offered on other trims of the same vehicle for the same model year. In your case, yes they can do it. After all, the lift and suspension on the Trail Boss can be installed on all other Silverados 2019+ as a GM Accessory item. It is therefore safe to assume the customer would want to upgrade the wheels and tires to the one on the Trail Boss, too. If the dealership wants to act stupid, go find another dealership. Your cash is just as green at their competition. Their loss is their competition's gain. The best part about stupid people is there's always somebody else smarter than them. Allow them to suffer from their own stupidity instead of trying to fix them. Hopefully at some point Darwin will come along and fix the problem.

newdude · October 13, 2022

47 minutes ago, RushTheBus_ said:

I have a 2019 silverado 1500 RST with 265/65/18 tires that I just upgraded to 275/65/18 (stock trail boss size). I want to get the speedometer adjusted to this tire size for piece of mind with odometer/speed/fuel econ. I spoke to someone at my local dealership a while back and they said they have to order a GM part that is ~$150 for that specific tire size to reflash the ECM. I called back today to get this done and they acted like they have no idea what I'm talking about. I am not interested in getting a chip to possibly void my warranty. Does anyone have any knowledge on what exactly I need?

GM will only calibrate to a tire size that would have came on the truck from the factory, or if doing an accessory tire size.

Being that 275/65R18 is an accessory size for one of the wheels they offer, GM would have a calibration file available to flash the truck.

However...is it worth spending all that money for a 0.9mph difference?? I sure don't think so. 265/65R18 is 31.6", 275/65R18 is 32.1". At 60mph its 0.9mph off. The two sizes are within 1.6% of each other.

Amcguy1970 · October 13, 2022

1 hour ago, Transient said:

First, a chip won't void warranty unless the chip is the cause of a failure or problem. A warranty can't be voided for aftermarket products installed, just not honored due to breach of warranty. This is federal law titled Magnuson-Moss Warranty Act.

Got some problems with the above statement cancelling out points you try to make.

1) So it won't void, unless?

2) Can't be voided, just not honored?

See where the confusion lies?

That is the thing, people love to say it won't void your warranty, then quote the magnuson act. Then right after say it can void if directly related, which means it can and does void part of your warranty...

Tyler

Edited October 13, 2022 by Amcguy1970

Transient · October 13, 2022

3 hours ago, Amcguy1970 said:

Got some problems with the above statement cancelling out points you try to make.

1) So it won't void, unless?

2) Can't be voided, just not honored?

See where the confusion lies?

That is the thing, people love to say it won't void your warranty, then quote the magnuson act. Then right after say it can void if directly related, which means it can and does void part of your warranty...

Tyler

I understand legalese is difficult for some people to comprehend. That doesn't mean the statements are canceling each other out.

Transient · October 13, 2022

3 hours ago, newdude said:

GM will only calibrate to a tire size that would have came on the truck from the factory, or if doing an accessory tire size.

Being that 275/65R18 is an accessory size for one of the wheels they offer, GM would have a calibration file available to flash the truck.

However...is it worth spending all that money for a 0.9mph difference?? I sure don't think so. 265/65R18 is 31.6", 275/65R18 is 32.1". At 60mph its 0.9mph off. The two sizes are within 1.6% of each other.

Your post is 100% on point. There is something I believe that should be added. Per GM in a document provided through GM Fleet (because that's where police departments purchase their vehicles), the speedometer has a variance of +/-2 mph at 60mph at 72°F. 0.9 mph may not seem like much, but added to the variable it could be the difference between a ticket or no ticket. And, the majority of highway speed limits are north of 60mph. In some states it's as high as 85mph. Buyer beware, and I agree with your point that the benefit may not justify the cost, but that's just opinion and may not be relevant to the purpose of the OP.

KARNUT · October 13, 2022

You could always download WAZE to your phone. Program a destination it will show your speed. See how far off it is.

Edited October 13, 2022 by KARNUT

GETGONE · October 14, 2022

Rough Country sells a module that plugs in between the stock wiring and BCM. You hook it to your computer before installing and input stock size and new tire size and it adjusts for the difference. It can be unplugged and removed in a couple minutes if you need to take it in for service and are worried about it causing warranty issues.

Z45 · October 15, 2022

Quote

GM offers tire calibrations for tires that have been sized, tested and designed for the vehicle in question and its applications. Other tires that do not meet these qualifications will not be supported and tire calibrations will not be available.

To determine if a tire calibration is available for a vehicle where a different tire and wheel size is desired, check the sales order guide in the dealership’s sales department. If a vehicle can be built in the sales order guide using the same make, model year, and trim as well as meet any restrictions in the tire section, GM will have a corresponding calibration available.

For example, a customer with a 2018 Colorado 2LT Crew Cab built with 255/65/R17 size tires would not be able to install a set of wheels and tires from a 2019 Chevrolet Colorado Z71 with 265/65/R17 size tires. Based on the sales order guide, the 2LT trim is only available with either 255/65/R17 or 265/60/R18 size tires. For this reason, a calibration will not be offered for this application.

TIP: When changing the tire size for new vehicles prior to the first sale and/or to a tire and wheel size that may require a different pressure or alter the cargo carrying capacity of the vehicle, refer to the latest version of Bulletin #12-00-89-007.

Once the tire application has been confirmed per the sales order guide, contact the Techline Customer Support Center (TCSC) to determine calibration availability. Tire and wheel changes are not covered by the manufacturer’s warranty.