What's the lowdown on re-calibrating ECM for larger tires (I searc

[BillaVista]

I read 20 or so pages but couldn't find any definitive info.

 

What's the low down on recalibrating or reprogramming the ECM/computer for larger tires? My 07 2500HD Classic came with pretty small 245/75R16. When it's time, I'd like to go 265 or 285.

 

What systems will be affected? Can the ECM be reprogrammed to compensate? Will the dealership do it? If not, what will be the consequences other than speedo and odometer error?

 

Will there be warranty issues?

 

What does everyone do?

 

Thanks,

 

Bill

[Hammer2785]

The largest a dealership can reprogram is to a 265/75 tire. I went to 285/75 from 265/75 and the dealership could not redo the calibration.

[schmuly]

Hi my 99 Z71 came with the 245's (factory) and I used my GPS to see if the speedo was correct. It was out so I swapped the tires to 265's and the speedo was almost 100% correct. But errored in the other way . This was two years ago and no problems at all. no re-calibrating just tire swap. I have 257,000kms and no major problems .

schmuly

[ShakinLM7]

Changing the width of your tires usually doesn't affect the height, & if it does it's usually only a quarter of an inch added to the total tire height max! A major difference in tires size from your stock tires is what will cause your speedo to be off. Here is a website you can play with to help you get a better idea of how tire sizes work and how they affect your speed, I suggest everybody check it out, it will show you side by side comparisons of your stock wheel to any size tire you choose. It also give's you a list of tires avalible in the selected size.

[eyeball03]

I'm running 275/55/20 on my 03, of course, came with 16". I changed the tire height with my HPP3 to correct the speedometer. Made a hugh difference, wish I'd done it sooner!

[ShakinLM7]

Changing the width of your tires usually doesn't affect the height, & if it does it's usually only a quarter of an inch added to the total tire height max! A major difference in tires size from your stock tires is what will cause your speedo to be off. Here is a website you can play with to help you get a better idea of how tire sizes work and how they affect your speed, I suggest everybody check it out, it will show you side by side comparisons of your stock wheel to any size tire you choose. It also give's you a list of tires avalible in the selected size.

 

 

Scratch that! I dont have much experience when it comes to sizing tires on smaller wheels with large aspect ratio's just 20's and 22's

[KB06YUKONXL]

I put 17" Z71 wheels on my 02 Suburban with bigger tires...BUT I called the Dealer first before I bought the tires to make sure they could re-calibrate the ECM to the size. There were only 2 or 3 possible sizes on mine so make sure you ask first. The re-program effects the entire drivetrain/abs braking system so it is a necessary update to have done.

[TBLAZER]

Many if not all late model GM vehicles tire size can no longer be recalibrated with out getting a special code from GM to recalibrate the vehicles computer,GM will charge the dealership for the new calibration code and the tire size has to be on GM's approve list.

The other alternative is to go aftermarket and get a power programer that has tire size calibration capabilities.