Dealer recalibrate speedometer for bigger tires?

[Hunter79]

I recently just added a 6 in lift kit and 35 in tires. I was wondering if the dealer could recalibrate the spedometer so I don't have to use an after market tuner and ruin the warranty I payed extra for on the computers. I know how to calculate what speed i'm going just not how off the odometer is going to be. Those are the two questions I am concerned with and as always all replies are greatly appreciated.

Edited October 5, 2015 by txab

[jstev4610]

Mine will not. The only option they offered was re flash with an optional tire size that gm already has a program with it hard coded. I asked about making the singular change using my hp tuners software and got the you don't want to invalidate your warranty comment.

[Hunter79]

A nearby dealer sells some lifted 2014/2015 sierras I didn't lift the truck through them but I would assume they wouldn't sell a truck with the spedometer and odometer being off due to the lift

[Z45]

Oversize tires require a special calibration that is not available to the GM dealer. I am sure those trucks they are selling have been altered by the upfitter and not GM.

[Robert.jean1]

Mine told me they would if GM supplied the calibration codes. They said that they can only calibrate using their programmers to a tire supported as standard or optional equipment. Dealer also stated that when they lift trucks they buy a speedo calibration tool specific to the truck that was lifted.

[newdude]

What others have said. GM can only calibrate tire sizes that are supported as OEM sizes for that specific vehicle.

[WilliamBos]

So if one went from 20" down to 17", a dealer could do it?

 

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[robvas]

Mine told me they would if GM supplied the calibration codes. They said that they can only calibrate using their programmers to a tire supported as standard or optional equipment. Dealer also stated that when they lift trucks they buy a speedo calibration tool specific to the truck that was lifted.

Yea, any handheld tuner can do it

[Robert.jean1]

Correct except for the programmers provided to the service department at GM. They have to purchase an aftermarket one and if doing that a person should just buy their own and avoid the service cost of having a GM mechanic do it.

[Hunter79]

Thank you for all the replies! Now my main concern is how off is the odometer going to be. Would the bigger tires be adding mileage to the computer or hiding some mileage? Is there a formula I can go by to know how many miles are truly are being added to the truck?

[Robert.jean1]

http://tire-size-conversion.com

Use that it is not perfect due to there being a difference between manufacturers actual sizes but you can compare tires and it will give you a pretty dang good understanding of the effect your new tires will cause.

[JCJ]

I recently just added a 6 in lift kit and 35 in tires. I was wondering if the dealer could recalibrate the spedometer so I don't have to use an after market tuner and ruin the warranty I payed extra for on the computers. I know how to calculate what speed i'm going just not how off the odometer is going to be. Those are the two questions I am concerned with and as always all replies are greatly appreciated.

How is it what off set did you use on rims any major rubbing ? I lifted mine and still waiting for my rims and tires to come in. 35x12.50r20 is what I went with Pvd vision warrior wheels and toyo open country mts

 

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[Jerry's Denali]

Dealer can do it.

I've had mine changed twice.

Edited August 2, 2015 by jericbarg

[Badass69]

So if one went from 20" down to 17", a dealer could do it?

 

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Realistically in the oem world the overall tire diameter on the trucks is pretty well identical regardless. Rim size doesn't matter at all. What matters is overall tire diameter. If you go bigger than any oem size gm does they won't be able to set the speedo and odometer with the factory tool. They will have to use an aftermarket programmer of some kind.

 

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[TJay74]

There is no optional tire size from GM, GM uses the same calibration for all of the tire sizes they offer across the line. They go off of circumference and revs per mile and that measurement is the same for all of the tires sizes GM offers. The loop hole of them changing tire sizes was eliminated on the 2014+ trucks.