Speedometer Cailbration

[ztsmith86]

What is the cheapest way to have my speedometer recalibrated for the over sized tires I have put on my truck? I'm clueless on the easiest way to have this corrected.

[LSR Mike]

It should corrected via the computer, The dealer or an aftermarket software such as Super Tuners or superchips etc...can do it

[TJay74]

The dealer cant correct the speedo calibration. GM uses the same over all tire height for all tires offered on the trucks so the calibration info is the same in all of the ECM's.

 

Hypertech makes a speedo calibration and customer tuning can fix it as well, but say bye to your powertrain warranty if you ever have any issues and GM sees that the ECM has been tuned.

[ztsmith86]

Dealerships sells these trucks with ovesized tires all the time. Wouldn;t they have to have the speedo corrected before they sell it to the customer? The dealers must use tuning software or some method to calibrate these before they leave the lots if they have outfitted them with oversized tires ... right?

[LSR Mike]

tire size and gear ratios can all be changed... do a search on google... Hypertech is in the duramax forums...guys are putting 35 inch tires on their trucks.

[TJay74]

Yes tire size and gear ratio can be changed, but not via the dealer. The dealer can only flash what the OEM off of the manufacturing line calibration was for the vehicle. They have no way to change the tire size or gear ratio.

 

My guess is the dealers selling trucks with lifts are either using the Hypertech module or not doing anything at all. Either way, if you use the Hypertech module it will change the stock calibration and will trip the flash counter. If you ever have a powertrain issue and GM request the calibration data and see the flash counter tripped you take a chance at denial of coverage.

 

The info is there for you to read, now you have to decide if putting over sized tires and correcting via a hypertech module or custom tuning is worth the chance of losing your powertrain warranty.

[colton_m]

I called the service manager at my dealer regarding this. He told me it wasn't a problem, and that they just "buy the software from GM" told me it would cost $150

[TJay74]

He is full of it, I have already went down this road with my dealer who I have used for 20 years. I would challenge you to ask him if he is using the GM global website to change your programming with a factory GM calibration. I can promise you he will say no.

[david722]

Buy the Abbot Electronic Ratio adapter (ERA). Mainly used for gear ratio changes and abs light and warning light fixes.

I just installed one today because I went from 3.23 to 3.73 and had my abs light on, warning chime dinging 34 times, and service brake system warning light on.

[MikeNH]

There is a way to do it out there but it may not be readily accessible- all the licensed gm upfitter who sell lifted trucks to dealerships have a recall rated speedo and that's done with GM software.

[Jerry's Denali]

There is a way to do it out there but it may not be readily accessible- all the licensed gm upfitter who sell lifted trucks to dealerships have a recall rated speedo and that's done with GM software.

 

Any dealer can do it. I had both of mine done.

[2014MallCrawler]

Tune it! :-)

 

The dealerships here use the Hypertech speedo calibrator and include it in their price of a lift etc.

[EaZ8]

The dealer cant correct the speedo calibration. GM uses the same over all tire height for all tires offered on the trucks so the calibration info is the same in all of the ECM's.

 

Hypertech makes a speedo calibration and customer tuning can fix it as well, but say bye to your powertrain warranty if you ever have any issues and GM sees that the ECM has been tuned.

no they dont.

the 17s that came on mine are 255/70/17 which is 31.1" tall and 10.04 wide

the 20s that come on some stock i believe are 275/55/20 which is 31.9" tall and 10.83 wide

you are looking at almost a inch taller and wider, then there is the stock 22" upgrade, 285/45/22 which is 32.1 tall and 11.22 wide

personally, ive never calibrated any of the vehicles ive had over the years, and none were stock tires or sizes.. usually about 5% off.

when using km/hr its easier to do quick math to know how fast you are going, if you have tires that make you go 7% faster you would show 100 when doing 107km/hr, city roads are usually 50 or 60 km so call it plus 3 or 4 km/hr.

[TJay74]

no they dont.

the 17s that came on mine are 255/70/17 which is 31.1" tall and 10.04 wide

the 20s that come on some stock i believe are 275/55/20 which is 31.9" tall and 10.83 wide

you are looking at almost a inch taller and wider, then there is the stock 22" upgrade, 285/45/22 which is 32.1 tall and 11.22 wide

personally, ive never calibrated any of the vehicles ive had over the years, and none were stock tires or sizes.. usually about 5% off.

when using km/hr its easier to do quick math to know how fast you are going, if you have tires that make you go 7% faster you would show 100 when doing 107km/hr, city roads are usually 50 or 60 km so call it plus 3 or 4 km/hr.

 

 

I have looked at several stock tunes on the HP Tuners site, all of the trucks are using the same info as the difference is minor. GM has done it this way for years.

[EaZ8]

 

 

I have looked at several stock tunes on the HP Tuners site, all of the trucks are using the same info as the difference is minor. GM has done it this way for years.

same software i believe, however they do not use the same overall tire sizes.

i would guess and say they set the speed somewhere between the smallest OEM tire size and the largest OEM tire size.

the 255/70/17 vs 285/45/22 is 3.36% difference in speed, if GM sets the speed to be accurate at 1.68% over the smallest tire size that is a very small % that it would be off for all the tire sizes (which is most likely what they do)