2007 new style GMC 2500 HD 4x4.  I know this is hard for you to answer Rick, seeing as how you drive those old rusted out jeeps and this is a newer vehicle....but I have faith all the same.  LMAO.

Have never seen sooooooo much confusion over this subject.  Googled till death.  Mixed opinions abound.  Some say you have to calibrate larger tires (P245-75R16 to P265-75R16) for the anti-lock brake system, not so much the speedo, to work.

Problem is I cannot get a straight answer from anyone, including the multiple dealerships I have called to ask.  Called 3 GM dealers.  First said yes,no problem.  Second said NO, can't be done.  Third said you don't need to, the larger tire is not large enough to make a difference.

Online solutions just as confusing.  Some say yes you can.  Some say no you can't.  I have no where else to turn but to the Master of Disaster, the orignal answer man himself, no introduction needed, weighing in at (how much your junkie jeep weigh?), Rick, the MAN with the PLAN.

HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 

 Seeing as I've never even owned a Jeep... I'll let that slide though, as many unknowing, rookies will mistake a Toyota FJ40 Land Cruiser for a Jeep from time to time. I did a little digging / research on my end and came up with mixed, similar results. So... I put a message into one of the engineers at GM to see what they say. It's a crap shoot as to *When* they get back to us. Sometimes they get back the next day, sometimes it's a few weeks. Ugh. The question is, what size tires did you go from, and what size tires did you go to? Congrats - you've stumped me on this one... RW

See, I got you so choked up over calling your Land Cruiser a Junkie Jeep you missed the second paragraph completely where I listed the tire sizes for you.  P245 75r16 to P265 75r 16.  Just one size up.  Not a real biggie.  Could care less about the speedo, mainly worried about the anti-lock system, as supposedly, its based on revolutions and the larger tire size could throw it off.

Yes, I knew it was a Land Cruiser (as far as I 'm making you think right now) all along.....

Also I noticed I went from Street Queen to Body Lift.  Was that an attempt to entice your favorite plumber back to the site to jazz it up some since it's sooooooooooooooooo boring around here???

 OK, so you're only adding 1" to the overall tire size - NOT a big deal. 

I haven't heard back from Chevy yet, so here is my suggestion. Take your truck to the Chevy dealer after you had your tires installed and tell them you want it recalibrated. Go to the 1st dealer that said they would do it, and have them do it. Anti-lock brakes aren't something you want to gamble with. 

This way you're covered either way. 

Rick