Put bigger tires...know what

Big Joe · November 12, 2002

Ok, I have a 2001 GMC 2500 HD Ext Cab with the 6.0 Motor and Automatic Trans.... I put new tires and wheels on it... Weld Stone Crusher Wheels 16X8 and I went with the BFG AT KO's 285-75-16's... Yesterday I went by a police car that had one of those Speed Checkers on the back and it was about 7 MPH off of what my spedo said.... Is this something that can be fixed with the 285-75-16 tires on there??? Any help would be greatly apprectiated......Thanks Joe

Shaners · November 13, 2002

You will have to get your computer recalibrated. Unfortunatly GM won't/can't do it for you. You can purchase a Hypertech and do it yourself (along with alot of other performance mods), but it'll set you back $250-$300 for the handheld computer.

I don't know if anybody else makes something for your application, but I bet they do. So for the time being please slow down a little.

Remember when you calculate your fuel milage you are going to look BAD unless you add in all those miles that you traveled and were never recorded on your odometer.

Firetiger(MN) · November 13, 2002

JET Performance Products makes a module to correct for bigger/smaller tires. SCU2000

I have the same size tires on my truck, and also aware of the speedo differences.....off more at higher speeds than lower....and TRY to remember that as I'm driving.

This module is much cheaper than the Hypertech if calibrating your tranny is all you are looking for. I have this on my list of things to get as well. Let us know if you try it and how it works.

Good Luck :thumb:

hogger999 · November 13, 2002

Unfortunatly GM won't/can't do it for you.

I think it depends on which service center you take it to. The first place I went said it was impossible. The second place I went said they would only allow 265'sand that it could only be done once. After that, I would have to stay with that tire size. Then the last place said no problem and that they would charge $60.

DamianSolomon · November 13, 2002

Most of today's modern auto computer reprogrammers have the option to recalibrate for larger tires and transmission shift points. Hypertech, Superchip, Jet to name a few. I am beginning to lean towards the Superchip handheld due to more programming capabilities and even a cheaper price over the Hypertech. There is an online dealer selling them for $295.00. Anyways good luck. PS. would be nice to see your truck, Weld Stonecrushers are nice wheels!

1BADHD · November 13, 2002

As stated above. Yo can buy some sort of computer tuner to get your speedo correct. But you also get the benefits of other performance tuning. There is one not mentioned yet, if you want to adjust your speedometer only, I think Superlift makes a unit to calibrate it. I thinks its called "TruSpeed". Here is a link. It is towards the bottom of the page. Super Lift TruSpeed

HendyPhoto · November 13, 2002

I took mine to the dealer and they calibrated it for 31x10.50's, that was the biggest tire that was on his little option screen on the computer. But it made it ALOT closer, now I am only 5 miles off at 40 MPH, so I just calculate in my head from there. I used to be like 8 or 9 MPH off. I have 35x12.50's right now, is there a module for that size?

1BADHD · November 13, 2002

I took mine to the dealer and they calibrated it for 31x10.50's, that was the biggest tire that was on his little option screen on the computer. But it made it ALOT closer, now I am only 5 miles off at 40 MPH, so I just calculate in my head from there. I used to be like 8 or 9 MPH off. I have 35x12.50's right now, is there a module for that size?

I believe the Superlift unit can do that size.

BDBWTE · November 13, 2002

Ok, I have a 2001 GMC 2500 HD Ext Cab with the 6.0 Motor and Automatic Trans.... I put new tires and wheels on it... Weld Stone Crusher Wheels 16X8 and I went with the BFG AT KO's 285-75-16's... Yesterday I went by a police car that had one of those Speed Checkers on the back and it was about 7 MPH off of what my spedo said.... Is this something that can be fixed with the 285-75-16 tires on there??? Any help would be greatly apprectiated......Thanks Joe

phww I'd disconnect the #### thing...go by the feel of the road to get your speed....you laughing but half of the trucks I drive don't have speedo's but some have two tachs....lol I don't even look at my speed I just go.. :thumb: