I put 265s on, and am off 5% according to my gps. Anyone else told this?


Thanks in advance

The dealer cannot reprogram the speedo to correct for tires. You will need to get it done in the aftermarket or live with it that way.

On the bright side you get 5% extra warranty for free. http://www.dieselplace.com/forum/smileys/Big Smile.gif

I'm in the same boat as you, GPS & 265s. And as Max Power said, your warranty will last longer since your odometer won't rack up the miles as fast as it should. http://www.dieselplace.com/forum/smileys/Wink.gif Trust me, you get used to your speedometer not being accurate, but with your GPS, you know your true speed.

Just don't forget to add those miles when you calculate your fuel mileage. (Your DIC won't be accurate.)

Actually they can with the tech 2. I was just in and talked with my tech he said he just did one for a new truck that the customer bought tires from them at delivery.

Actually they can with the tech 2. I was just in and talked with my tech he said he just did one for a new truck that the customer bought tires from them at delivery.


There seems to be a lot of dealers that say they can't adjust for 265's. This sounds a little strange since some of the new 3500 trucks come with 265's.


It would be great if one of our resident GM Techs could give us detailed instructions on how to setup/use the Tech II to adjust for 265's. We could then take those instructions to our dealerships and put an end to their excuses. This could be a Tech II training issue http://www.dieselplace.com/forum/smileys/Confused.gif.

The Tech II will allow the dealer to reset the ABS for the new tires but it doesnot correct the speedo on the Duramax. GM does allow for tire correction on some versions of gas powered trucks but not all of them. It's kind of hit and miss at this time.http://www.dieselplace.com/forum/smileys/Confused.gif

Is it something they are gonna have down the road, or is there anyone here in upstate ny that can reprogram my ecm with aftermarket?