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I’ve got an 06 Suburban 2500 4x4 8.1L with a 4:10 rear end. I pull a 6500 lbs travel trailer with it. Before this Suburban I had two others with the 3:73 rear end. With those on long grades they’d have to come out of overdrive. With this one I can pull long grades just fine in overdrive and it doesn’t do the annoying shift down constantly like the 3:73s did. But I’m do for tires soon and was thinking about upsizing from the recommended 245/75R16 to 265/75R16. I know that by upsizing I’m going to reduce the torque. Has anyone done this and noticed a difference with the tow? I don’t want to upsize then get stuck with the constant down shifting on grades again.
 

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@Jaercole I don’t think going from a 245 to a 265 is gonna cut your torque that much. I’m running 315s, and you lose less torque thru that 4l85e than I do thru the Allison with the big block. My truck doesn’t care. One thing I wish I’d done would be get it tuned. That’ll give you the torque back and reset your speedo for the tire size increase.
 

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Heres a tire size calculator that I use to help me figure out tires.

Al

 

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Actually those are the same tires I have on my burb there is only a 3.9% difference, meaning they travel 3.9% further than oem, so at 65 your actually going 67.5. So I conclude that the difference is so small and under 5% that this size is absolutely fine. I bought a set of bridgstone dueller A/Ts that I though were oem size but I was wrong. It turned out just fine though and I really like them.

Side by side the 265's would be apx. 1.25" taller.

I always check vehicles speed with a gps app just to see where it actually sits, my work truck was actually slower than the speedo said. That's good info to know....

Al
 

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What I learned by stepping up tire size just a little, was that it made almost no difference in pulling power. Initially I went with the 265/75's, but on my most recent tire replacement I decided on something a bit different. I went for the Cooper commercial offroad tire, in size 255/85-16. First off, it's an excellent tire, very capable, very tough. Second, the size choice is likely the best move I've made.
I changed out the factory 3.73's several years ago, went to 4.10's. While my pickup has the NV4500, vs the automatic I think you have, I pull an 8500 pound fifth wheel, with few problems. I think you'd like the extra 1" plus sidewall height of the 255/85. I found no loss of stability with the increased profile.
An aside that you didn't ask for...... several transmission shop owners have told me the surest way to destroy a transmission (manual or automatic) is to tow in OD. Therefore, I don't.
My PU is a 99 K2500 with the 454.
Regards,
Bob
 

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The answer is it depends... the 8.1L with the 3.73 ratio differential will notice the tire size increase more than someone with the 4.10 rear gear. Unfortunately that is what I have. It also depends on how much you are pulling. 6500lb trailer is about what I pull, sometimes more depending on how much stuff I drag along for my mobile chassis dyno business. There are many times I wish I had the 4.10 ratio instead of the 3.73 with the 265/75 tires. With the 4.10 ratio I definitely would not go taller than the 265/75's.
 
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