Speedo recalibrate

[cford716]

Has anyone had a dealership recalibrate their speedometer? Mine is telling me they can't do it.

[tbarn]

Cannot be done via normal GM methods. Requires aftermarket solution.

[redwngr]

All the factory tire sizes have the same rev/mile so GM didn't need to give them he ability to change.

[Brian Long]

What ^they^ said. Neither the GM or SnapOn scan tools show the ability to change the tire size. I do not recall what the actual name of it is - think it is "VCI" or something like that - but the dealer can petition GM for a new file for your truck. If GM is willing to do it, it costs $50. I was told by one tech that he thinks they will only make a program for tire sizes that were available as an option for that particular year truck. My request for a new file was denied, even despite the fact that my truck is out of warranty.

 

You can buy aftermarket programmers that will do it. My personal experience is anything over a 34.5" tire programming freaks out the ECM causing the parking brake and anti-lock brake warnings to come on after a few miles. They are not actually failed, computer just thinks they are. YMMV.

[cford716]

I currently have 275/65/20 so I'm at 34". I'm only off between 3 to 5 mph so it's not too bad.

[TJay74]

No factory/OEM/Dealer option at all. As said GM uses the same rolling tire circumference for all of the tires available for that series truck. All of the tire sizes are with in a 1/4" or so of each other.

 

Tire size will usually will not trip off the ABS computers unless you are running a staggered tire size. Then if there is more than a 1" difference in the two tire sizes it will trip the ABS computer.

[cford716]

Had the same issue with my Fords, but they had some other tire options they could pick from so I was able to get very close. I said it before, these are trucks, not a Prius. People are going to change tires. No reason the manufactures couldn't set it up to just plug in a tire diameter.

 

I can see where they might not want to get into possible issues with very large tires on a lifted truck, but I'm on a stock truck.....come on!

[Cowpie]

The stock 265/70R18's on my 2500, the speedometer was about 1-2 mph faster than actual speed. When I put 275/70R18's on, it matches perfect now.

[Sierra Jon]

So what is the best programmer to do this? I've seen the countless threads on programmers but I really just want to recalibrate the speedo...

 

Sent from my Nexus 6 using Tapatalk

[cford716]

So what is the best programmer to do this? I've seen the countless threads on programmers but I really just want to recalibrate the speedo...

 

Sent from my Nexus 6 using Tapatalk

X2

[Cowpie]

I have heard of many folks changing tire revs per mile with the DiabloSport tuners. No experience with it myself.

 

https://www.diablosport.com

[geektoad]

Hypertech sells a "tuner" that just does speedo recalibration, but it's over $200. That's crazy unless you're going significantly out of spec.

[Kent2500]

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[Chebbyfan]

The stock 265/70R18's on my 2500, the speedometer was about 1-2 mph faster than actual speed. When I put 275/70R18's on, it matches perfect now.

Mine had the 18s too. When I switched to the 295/55/20s my speedometer is almost dead nuts right on too.

[Marc Russ]

The stock 265/70R18's on my 2500, the speedometer was about 1-2 mph faster than actual speed. When I put 275/70R18's on, it matches perfect now.

 

What made you check it to see if it was accurate in the first place and how did you check it?