Speedometer calibration with 22 in rims

ShamrockShooter · March 25, 2017

My 16 silverado came from the factory with 22 inch GM rims. The sticker on the door sill says 22 inch rims 285/45/22. Does anyone know if GM calibrates the speedometer especially for the 22 inch rims? The 22s are about 1.6% bigger circumference then the standard 265/70/17 or 265/65/18s that come on most trucks. Over 100,000 miles that is a 1,600 mile difference on the odometer?

I will be switching to 265/65/18s and selling my 22s. So either it will be back to normal if GM doesn't calibrate for the 22's or my speedometer will be off by 1.6% if it was calibrated to the 22s. I know it's not that big a difference but perhaps the dealer can reprogram to the correct size as long as I am using a standard gm rim and tire size?

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Luster · March 25, 2017

I see you've done your homework! With a only 1 mph difference at 70, I seriously doubt that GM took the time or expense to change calibration for different tire diameters. Just my opinion.

(Any luck trading your 22's for 18's? )

Sierra706 · March 25, 2017

The dealer can calibrate between the two

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tmo · March 25, 2017

The dealer can calibrate between the two

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I was told that they can't calibrate them when I replaced my 17s. I just went to 20s so it wasn't a big deal, but seems strange.

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Sierra706 · March 25, 2017

I was told that they can't calibrate them when I replaced my 17s. I just went to 20s so it wasn't a big deal, but seems strange.

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They can calibrate them to factory sizes. So the 17, 18, 20 and 22 sizes that come from GM. Confirmed by my service manager

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ShamrockShooter · March 25, 2017

They can calibrate them to factory sizes. So the 17, 18, 20 and 22 sizes that come from GM. Confirmed by my service manager

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Thanks. When I go in for my next oil change I will ask them to do it

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ShamrockShooter · March 25, 2017

I see you've done your homework! With a only 1 mph difference at 70, I seriously doubt that GM took the time or expense to change calibration for different tire diameters. Just my opinion.

(Any luck trading your 22's for 18's? )

No luck trading so I bought a set of midnight edition on ebay. Now I will sell the 22s and hopefully use the difference for an exhaust once I decide which one.

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ShamrockShooter · March 25, 2017

How do our trucks measure speed and distance? Is it based on drives shaft revolution?

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Rolling Thunder · March 25, 2017

How do our trucks measure speed and distance? Is it based on drives shaft revolution?

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Revolutions per mile:

http://www.gm-trucks.com/forums/topic/168005-gm-can-our-computers-be-update-by-dealer-for-larger-tires/?p=1960072

https://tiresize.com/comparison/

ShamrockShooter · March 25, 2017

So my 18s would go 11 more revolutions each mile compared to the 22s. Making the truck think it went further then it really did. After 100,000 miles that's an extra 1,600 miles.

Unless what I'm reading in that other thread is gm calibrates for an average of the two sizes?

This isn't really a big deal I'm just more curious how it works than anything.

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