What do i need to recalibrate my speedometer after my tire/rim swap?

[kbuskill]

Tech 2 can't change tire size on the GMT900 platform but I think maybe it can on the GMT800... not 100% positive on that though.

Tech 2 can change the tire pressure the TPMS looks for on the GMT900 however.

I know my Diablo I2 can change tire size/speedo calibration.

If you check CL you can find a used Diablo for a reasonable price, just make sure that it has been unmarried from the original VIN or you will have to pay $150 for another license.

 

[petethepug]

Interesting stuff. Found this on GMT800...

https://www.gm-trucks.com/forums/to...re-calibration/?do=findComment&comment=199725


If you dont change the "PCM calibrations for speed your ABS,engine power,cruise,speedo will all be wrong. You will not get the best mileage & power,antilock brakes wont work right and incase of a accident and your airbags going off it will set off bags at wrong force.
Dealer can calibrate your truck but if your making changes you might want to get a programer and tweek shift points on A4 fuel & timing.
I use the Predator http://www.runninwiththedevil.com/index.html on my Corvette and it works great. Cant wait for it to come out with one for 2004 trucks soon.

Interesting read if your going to convert your truck of 2500 Burb to hyrail (railroad use).

https://www.gmupfitter.com/files/media/photo/917/Bulletin_83c.pdf


Sent from my iPhone using Tapatalk Pro

 

[bigdog9191999]

the 100 is probably to unlock the vin for hptuners. if your close enough I have a copy and can do it for whatever it cost to unlock the vin (100 seems right.) can mod the trans tables a little also for that. I am not familiar enough with it to do a full tune yet however.

 

[Bill 1960]

~
If you dont change the "PCM calibrations for speed your ABS,engine power,cruise,speedo will all be wrong. You will not get the best mileage & power,antilock brakes wont work right and incase of a accident and your airbags going off it will set off bags at wrong force.~

Just my .02 that’s a sales pitch the tune gadget sellers pass around. While some of it is technically true, because the speed sensors do input to those systems, it’s mostly irrelevant. Take the scary part about airbags for instance. We’re talking deviations in the single digits percentage wise; human bodies vary a whole lot more than that.

My thinking on this is based on lifting many vehicles and fitting larger tires. I’ve got three in the yard right now, none with speedometer correction. 2004, 2008, 2019. No issues, other than the gauge error. I’ve also used HPTuners as well as other canned tune devices to make corrections. I won’t spend the money on a tuning device myself just for that particular reason. But if I’ve gotten a tuner for other reasons, I’ll fix the Speedo while I’m in there.

I’m sure others will have different thoughts, I just want to put my experience out there so people won’t have to rely on what the tuners will tell them without hearing a different perspective.