Is my Speedometer Correct? (wheel/tire change)

[AlDAngle]

3 hours ago, newdude said:

 

If you want to keep the 18"s then yes the dealer can go back to a calibration for those wheels/tires.  If you want the 22"s that were supposed to be there, leave it alone. 

 

They will have to program the ECM, the BCM, the Electronic Power Steering Module and the front camera module if it has one.  They will have to call GM Techline and get a programming authorized on it. 

Thanks a million newdude!

 

I'll post an update when the matter is resolved.

[TJay74]

On 10/14/2019 at 10:42 AM, MaverickZ71 said:

It will require a PCM programming change.  You can either pay a GM dealer to do it, or you can buy a Hypertech or Diablo or other aftermarket tuning device that has the capability to adjust between tire diameters.  A few hundred $ either way.  The dealer you purchased from should have had the intregrity to reprogram the truck for the new tires before you bought it, so the speedometer/odometer would have been correct.  All they did was do a swap for somebody else who wanted bigger wheels and it left you in the lurch.  

 

The dealer does not have the ability to change the tire size in the ECM, they havent since the K2xx platform came out in 2014. GM uses tire sizes that are close enough in overall height and rolling circumference to where they can use the same calibration data across all of the factory tunes.

[TJay74]

OP I will say this, by law the dealer is required to make you whole again on the wheels and tires. If they took the upgraded wheels/tires off of your vehicle for another vehicle and the vehicle window sticker/invoice shows the vehicle should of have came with them then the dealer is required to discount your truck the amount those 22" wheels cost or else put the 22" wheels back on the truck.

Buddy bought a 15 Camaro. Drive it home and drove it for about a month. It had the basic steel wheels on it even though it was a RS V-6 model. After several weeks he got to looking at the invoice and it showed the car was supposed to have 20" wheels and tires on it, it had the basic steel wheel 18" setup on it. When he showed it to the dealer they had to make him whole again, so they ended up putting a brand new set of 20" wheels and tires on the car at no charge.

[AlDAngle]

10 hours ago, newdude said:

They will have to program the ECM, the BCM, the Electronic Power Steering Module and the front camera module if it has one.  They will have to call GM Techline and get a programming authorized on it. 

 

1 hour ago, TJay74 said:

The dealer does not have the ability to change the tire size in the ECM, they havent since the K2xx platform came out in 2014. GM uses tire sizes that are close enough in overall height and rolling circumference to where they can use the same calibration data across all of the factory tunes.

 

Well, now I'm really confused. 

[becker87]

Just put 275/70/18 duratracs on my RST instead of the factory 265s that came on it. Looks like my speedo is off by about 2 MPH. How much will that throw off my calculated mileage on my truck? I understand of losing a few MPGs from the bigger/ heavier tire but it seems that my mileage has really tanked. Havnt driven enough for a hand calculated test yet.

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[MaverickZ71]

17 hours ago, TJay74 said:

 

The dealer does not have the ability to change the tire size in the ECM, they havent since the K2xx platform came out in 2014. GM uses tire sizes that are close enough in overall height and rolling circumference to where they can use the same calibration data across all of the factory tunes.

I know that was true for the 265/17, 18 and 20 inch factory sizes--they were all the same diameter tires.  But not for the optional 22 inch?  Certainly not for the 22 inch tire size the OP listed, when you calculate it out.  

[newdude]

17 hours ago, asci computer said:

 

 

Well, now I'm really confused. 

 

Lets see if I can clarify.  Your truck was ordered with 22" wheels as a dealer installed accessory correct?  You seemed to indicate that in your original post. 

 

If that is indeed the case, your truck's ECM, BCM and Electronic Power Steering module are all calibrated out of the gate for the 22" wheels, which use a 275/50R22 tire equating to a 33" tire.

 

You now have 18" wheels that the dealer popped on there.  I assume the tire on them is a 265/65R18, which is 31.5". 

 

GM has two factory calibrations based on their tire sizes.  The 17" and 18" wheels use one calibration, and the 20" and 22" wheels use the other.  

 

IF you want to keep those 18" wheels, and assuming they are 265/65R18 tires, your dealer will have to call GM Techline and get authorization to calibrate your truck's modules to the calibrations for those smaller tires. 

IF you want the 22" wheels that were supposed to be on the truck, leave the truck alone as far as calibration.  If you don't want to mess with recalibrating, you can always swap to a different tire size on the 18" wheels, so you could switch to a 265/70R18 or 275/70R18.   

[AlDAngle]

9 minutes ago, newdude said:

 

Lets see if I can clarify.  Your truck was ordered with 22" wheels as a dealer installed accessory correct?  You seemed to indicate that in your original post. 

 

If that is indeed the case, your truck's ECM, BCM and Electronic Power Steering module are all calibrated out of the gate for the 22" wheels, which use a 275/50R22 tire equating to a 33" tire.

 

You now have 18" wheels that the dealer popped on there.  I assume the tire on them is a 265/65R18, which is 31.5". 

 

GM has two factory calibrations based on their tire sizes.  The 17" and 18" wheels use one calibration, and the 20" and 22" wheels use the other.  

 

IF you want to keep those 18" wheels, and assuming they are 265/65R18 tires, your dealer will have to call GM Techline and get authorization to calibrate your truck's modules to the calibrations for those smaller tires. 

IF you want the 22" wheels that were supposed to be on the truck, leave the truck alone as far as calibration.  If you don't want to mess with recalibrating, you can always swap to a different tire size on the 18" wheels, so you could switch to a 265/70R18 or 275/70R18.   

You have everything 100% correct with regard to my Silverado's wheels and tires. Thanks for the clarification, I really appreciate the information you provided.

 

Years back, one of my Brothers in Arms decided to go at it (verbally) with a Captain. The Captain said to him "Richard, in a battle of wits, you're an unarmed man". Now that I have the info to go forward, I won't be Richard II. 

[Russ Currier]

I literally asked my dealer today if I swapped the DuraTracs off my truck for 295/70R18s if they could calibrate/reprogram to compensate for larger tires and he told me no. So what’s the answer, can they or can’t they. I realize there is a programmer out there, but now I’m concerned with my dealer knowing what the hell they can/can’t do with the truck ....


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