tire size opinions for 4.10 gears

I have a '97 T-100 5 speed; I took the original window sticker to Toyota and they told me the gearing is 4.10. It originally came with the 16" alloys and 265/70/16's from the dealer in '97.

I mostly drive very twisty roads in the mountains and snow in the winter.
a few options would be 245 75 15 a/t's in either p(4ply) or LT(10ply) ...nearly the identical height to 265 70 16.

I could get a 235 85 16 (10ply) that is an inch taller (like a 265 75 16) for better snow traction; or go with the 265 75 16 (4 or 10 ply)

any opinions appreciated regarding gas mileage and performance on twisty mtn roads/off road capability

( the 10ply tires are over 45lbs and 16.5 tread depth and the 4 ply are under 35 lbs with 13.0 tread depth)

thanks!

This advice is all very general and a bit rambley. I hope you find some of it helpful.

You might find this tire size calculator useful for comparing tires: http://www.miata.net/garage/tirecalc.html

Also remember that circumference = pi*Diameter (linear) so for every percent you increase/decrease diameter you are increasing/decreasing distance per tire revolution by a percent. You can use this to help determine how a tire size change will influence your speed in each gear relative to RPMs.

I don't have a 5 speed so my advice will be a bit vague here: Whenever your RPMs at high interstate speeds are not a concern, gearing down (weather it be through gears or tires) will improve performance. Since you're mostly talking about hills and twisties, decreasing diameter slightly might be what you want. My experience has been that for slight changes in tire diameter (all else constant) gas mileage stays the same. Increases in tire width very rapidly decreases gas mileage.

Snow performance is a big point of contention, but often people can agree on the following: if you're on thinly snow covered roads a narrower (not overly wide) tire is better. If we're talking a snowy tundra, the wider the tire the better. Off road of course you'd like wider.

Finally, a 10 ply tire may last longer, will have stiffer sidewalls, a rougher ride, and be harder to balance. a fewer ply tire may not last as long, but is generally fine if you're not doing heavy hauling. Personally, the last pair of ten ply tires I had (BF goody all terrain TAs) were nothing but trouble. They were impossible to balance, very expensive, and didn't last longer than a much cheaper tire. They sure looked nice though...

I'd go with a 4 ply because of a better ride (compared to a 10 ply) and less weight, and equivalent height as stock or just a little taller, to keep the engine operating in it's powerband to avoid losing power and MPG.

But that's just my $.02

helpful info.......

I will likely go with a P rated 245

-B.

i run 31-10.50 R15's with my 4.10 gearing, and it seems to do very well, still get good mpg's also, around 17-18

Im doing fine on 32-11.5-15 on the stock 15'' rims

Freestone

For about 10k miles I ran 33x12.5x15 with a 4" lift then I added 2" more and 35x12.5x15 and Ive been running that with the stock 4.10 gears for about 120K miles now with no problems I have a 5spd headers,cat-back and a k+n intake and still running strong with about 15 mpg.

LS1 T100