Questions on towing with a lifted truck

BurbMan wrote:

majorgator wrote:

BurbMan wrote:
Also be aware that taller tires will effectively decrease your axle ratio. Formula is the old tire diameter divided by the new tire diameter times the axle ratio. For example, I have 4.10's on my truck, and when I swapped out the factory 245's for 265's, the larger diameter tires reduced my axle ratio to an effective 3.92. I noticed it right away in that the trans wanted to downshift a little sooner on hills, and that's towing 8500 lbs. I wanted a little more ground clearance and traction off road, but didn't go to 285's because I didn't want to decrease highway towing performance that much. So the 265's were a good compromise for me. If I was hiway all the time I would have stayed with the OEM 245's. If I was offroad more of the time, I would have gone with 285's.

The tire size you're referencing is the width, not the height.
FWIW, on my '07 Silverado 1500, I went from 245/70 (stock size) tires to 285/70 tires at my first tire change. The truck improved in every way. Better mileage, better handling, better ride, etc. Nothing changed regarding shifting. The speedo is off by about 3 MPH when it reads 75 MPH. Below that, its negligible.

Absolutely INCORRECT. Overall tire diameter is what affects the rear axle ratio, the width has got nothing to do with that. Do some homework, maybe start here.

Look at Michelin LTX/MS as an example. LT245/75-16 has an overall diameter of 30.5". The same tire in LT285/75-16 has an overall diameter of 32.8". So if you had 4.10 gears in your truck, your new effective axle ratio with the taller tires is 3.81. To maintain the same pulling power with the taller tires, you would need to re-gear to 4.41's...in the GM world 4.56 would be closest.

Fact is, you have reduced the pulling power of your truck with those taller tires. You won't notice it empty, and if you haven't noticed it towing, then your trailer isn't very heavy. Of course in FL your biggest hill is an interstate overpass...

Dude, come on, read my post again. What I said is absolutely CORRECT. You referred to the tire WIDTH and referenced that as the tire HEIGHT. The second number in this method of tire sizing gives reference to the height. I never said anything about gear changes. Don't be so quick to justify yourself that you fail to read.

I'll stick with what I said about my truck. With over 200K miles on it, mixed with highway driving and towing of up to about 6K or 7K pounds, I beleive I can be an accurate judge of its performance. The calculator you linked to is not accurate. It depends on linear data input and provides linear data outputs. As stock tire size increases, the calculator becomes less accurate, because overall diameter increases become less of a factor. If you increase the diameter of a compact car tire by 2", then you've made a huge change. But when you increase a large heavy duty tire diameter by 2", you've created an almost negligible impact. A straight-line calculator cannot deal with this.