I have 265/70-17 tires, which are around 31.5" tall, stock fitment on my truck. If I went to a slightly larger tire - say a 285/70-17 at just under 33", or a 235/80 - 17 at the same diameter, would I expect unloaded highway cruise mileage to improve a bit? Would 285/75 tires fit on the stock wheels and not rub with a stock height truck? They are around 34" tall.

Thanks, Brian

 

Probably not, the change in gearing would be offset by the heavier weight of a bigger tire

 

Agree with Ian on this one, rolling mass will not improve the MPG

 

Benefit of lower RPM's on the straight and level could be off set by more lugging and throttle (fuel) pulling the hills. Depending on where and how you drive you could see a small increase or even decrease in mileage.

 

I actually had to go do the math to follow you here: the 235/80s are close to what you now run (little taller) and I think you would see some gains with those tires which won't be, if at all, much heavier but will have a gearing advantage (particularly on flat ground) and a smaller profile for wind/road loss advantage over what you have now.

Anything wider and taller and I agree with the other guys...

 

Agree. My tires are MUCH heavier and larger than stock. Highway mileage did pretty well, but not as well as before. City mileage suffered greatly. I have over 600 lbs of tires and wheels to start at every red light. That sucks a lot of fuel. However, they act as a flywheel after they get going and will pull you right up an interstate ramp faster than you expected to go. It's a trade off, but you will probably come up short.
BTW Rusty, we came close to Enterprise earlier today coming back from the beach. I always wondered where it was and now I know.

 

As to the size question, you can usually find the recommended wheel width for the tires you're looking at on the manufacturer's website. I had 34.5" 265/70/19.5s on a 2wd with only a leveling kit and no rub. I bet you'll be fine.

 

Must have been on SR 231N to 65? Hard to believe we're this close and haven't been to the beach yet this year! (Have been to the lake though)

 

We pretty much hit 'em all, but I think we were on 45N. I saw a sign to turn left to go to Enterprise. My wife pulled up a map and there you were. I told her that that's the place to start looking for advice on truck problems if anything ever happens to me that doesn't total the truck too!

 

Agree 100%. Smaller road print equals slightly less resistance but can also diminish emergency braking.Everything is a trade off. Factory is usually a compromise of everything.