I should know the answer to this, but would this tire on an 8 inch wide rim be shorter than the advertised height since it was measured on a wider rim? I would assume overall diameter is smaller since the tire would have to pinch in farther with the 8 inch wide wheel. Here is advertised height and width. Cooper discover at3.
LT315/70R17 121 S D measured rim 9.5 width 12.65 height 34.35. Thanks.

 

The tire would actually be taller. As you pull the sidewalls in the tread of the tire "crowns".

 

I would agree that on a wider rim the tire would be a little shorter. Sidewall's would be pulled out a little more on a wider wheel. I ran 315x70x17's for year's on a 8" wheel with no problem's.

 

Did your old truck have the 3.55 or 3.73 rear end? I have 3.55 and don't know if I can justify the cost to regear as well when it comes time for new tires. I sold my travel trailer so all I tow is a 12 foot enclosed trailer. I may end up going with the 295/70/17, which I noticed u dropped to with the toyos so it won't be as hard on the transmission. I want the 315s as they are offered in a lot more tires than the 295s and would fill the wheelwells nicely. decisions, decisions.

 

My old truck had the 3.73's and were straining with the 315's. Getting an Edge programmer helped out but I found the 295x70's were a better match at 33.5 inches tall. The Toyo's were heavy at 73 lbs. ea. and netted me 1 mpg less then the 315's probably due to weight and MT tread pattern on the hwy.

 

Interesting that the smaller tire had worse mileage, but a little more understandable with it being a mt. Well thanks for the info.

 

315 70 17 on my stock wheels

 

They were smaller in diameter but heavier so I guess the stop and go driving killed the mileage a little. The best I ever got with the 315's was 18.1 on the hwy @60 mph with no AC on. This is the 315's on 17x8 wheels

 

What size lift do you have on there because I'm trying to run what you have but I don't know what lift I should get