I am looking into my next set of tires when my stockers finally wear enough to replace. I have an unlimited auto with 4.10 gears. I want to avoid regearing for the time being. So according to everything I have read, I want to stay between 33-34" diameter tires. With the actual tire diameter being dramatically different so often, I am looking for some help with the Cooper STT. The sizes are narrowed down to 315/75/R16 with list diameter of 34.47inches and 295/70/R17 with list diameter of 33.45inches. How accurate are these measurements? If pretty close, I will get the 295/70/R17. If over estimated, I will get 315/75/R16. Thanks in advance for your help.

 

Coopers stated sizes are very very close to what they actually are mounted, without weight. Once you add weight to the tire, its size will vary depending on the amount of weight applied.

 

Manufacturer's specs are usually accurate. The height variation in practice comes from mounting the tire on a different width rim, air pressure and vehicle weight.

 

I've got the STT's in 305/60r18 which is basicly a 33" tire but mounted on 18x9 wheels they physically measure out at 32" high.

 

Sounds like the Cooper STT mounted is pretty close to listed diameter. This would make the 315/75/R16 too close to the 35" tire I should avoid with the 4.10 auto. Thanks for the help so far, any new info appreciated as well.