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quote:Originally posted by tnorfitz
Just talked to the dealer and they can adjust the electronics so that the speed will read correctly with the 265's instead of the 245's on the GMC 2500HD.
My dealer also told me that you gain about 400 pounds of load per tire by going to the 265 tire. Anybody out there that can verify this info. I have been reading that the 3400RL on a 2500HD gets real close to the load limit on the 245 tires. Would it be a good idea to size up to the 265 before I put any miles on the truck??? Both the 245 and the 265 are E rated, 10 ply tires.
If I do change out the tires, I have a little concern about the Duramax and tranny with the larger size tires when I tow. Does that have an adverse effect on the pulling configuration( make it harder for the power train to operate)? I have never pulled with a diesel before.
Any help would be great!!!
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From the Michelin website you can find that 245s have a capacity of 6084lbs per axle, 265's have 6830lbs per axle. This is based on Michelin LTX M/S LT265/75R16 tires. So, assuming that the rear axle is the one of concen, you can raise the tire rating by 746 lbs. This does not change the mfr axle rating, but since the axle ratiing is the same as the 245 tire rating, you can assume that you have gained some margin of safety. (I am told that the 3500 usses the same axle, but I'm not sure about the frame and brakes). The 245's turn 681 revs per mile compared to 652 for the 265's, a difference of 29 revs/mile. This works out to 4.2% fewer revs, so I think your speedometer would read 2 or 3 mph low at 60 mph. My dealer also told me they could adjust the computer to account for 265 tires, that will also adjust the transmission shift points etc. The 3500SRW truck uses 265 tires, so they are not foriegn territory to GM.
The 3400RL actually has a fairly low pin weight for its size, so you should not have any problem supporting it on your truck.
All that said, keep mind that nothing you can do to vehicle can change the load ratings assigned to the vehicle by the mfr.