need clearance

Shawn T · August 10, 2004

I recently mounted 285/75's to my 03 GMC 2500HD and I need more fender clearance up front. I have owned a number of GM trucks with the IFS and I know what happens when you tighten up the bars on the front. I heard a rumor that on the HD's that the ride quality is not as badly affected as the 1500's and 2500's. If this is true I would like to crank them up an inch or two. If I do, should I have the camber and caster adjustments made to the front end. Also, with the DMax/Allison combo I've been told there is no reprogram for the DIC to compensate for the larger tires. Is this true, do I just have to "live with it", as I've been told by the dealer.

chadlyt · August 10, 2004

i can answer a few things for you.

I wouldn't crank the t-bars on a HD. I would go get the keys off of a 1500 and install them, then possibly get rear blocks if the front ends up higher.

You would need to get new shocks as moving up over an inch tops them out. Alot of guys go and get bilstiens or rancho 9000series after doing this.

I cranked my t-bars and it rode reallt rough. i had to go back down. I haven't had the time or $$ to even think about new shocks or keys.

I'm not sure about the tire question. I do know that with the allison, they dont reccomend the anything over 265's due to shift points and if you are under warranty. You would need an after market chip for that.

TXD · August 10, 2004

go ahead and crank them bars up. the ride doesnt change much, and if you change out the shocks with something better than factory that will almost make the change disappear. ive got pro comp Xterrain 285/75 on mine, swapped the tbar keys to get 2.5" lift out of the front and ive flexed the suspension pretty hard off road with 1 small rub that can be fixed by tying the fender well lining back.

Roofer · August 11, 2004

If you crank the T-bars make sure you get an alignment done. It does throw it off a bit and will wear your tires fast and abnormal. There is noreprogram for the speedo, but there are some chips and programmers that can help with that. Although your shift points will be the same as they are now. Some like it, some don't.

Machine · August 11, 2004

You shouldn’t have to crank the T-Bars to fit 285’s. The rubbing you’re probably getting is in the front portion of the plastic wheel liner? If so, pull the plastic forward and zip-tie it to the frame. Real easy and it works.

The only way to reprogram the speedo is by using an aftermarket programmer like the ones offered from Diablow and Quadzilla.

Good luck.