18 wheels on that semi or 10 ?????????????????????????????????

Duh, but tires are rated at cold inflation levels. Whats your point? If you have a 130 psi tire it will be 140-150 after a few miles. In either case inflation is above cold inflation, but tire manufactures know that. Now when your filling a tire the compressor needs to be able to create enough air at the cold inflation number. many are limited to 120 at truck stops. (al least the pilot ones) In any case, the 315 tire is not designed for use in a single drive configuration. There is no real benefit over the SS since the rr is almost the same.

 

Richter was not saying you are wrong,just gave some extra info.
There are newbies reading this too.

As to why 315's instead off SS's?
One thing that springs to mind is price?
I don't know current prices for either,maybe you do?

 

I know SS with mich advantage are around 950 a piece. I dont know 315's as i don't buy them. But, there would certainly be reduced tire life from trying to brake with a smaller surface area, so any savings in price will be diminished in needing to replace faster.