So what does it mean when a tire has two service description numbers?? I know what the number is (another way to list load capacity), but don't know what it indicates when they put two numbers for the same tire like '118/115'.

Additionally, what do you make of a tire with a N speed rating? Pretty low. The majority of truck tires seem to at least have a Q, but an N seems pretty low and inefficient.

 

I'd go do some reading at tirerack.com, they've got tons of useful info.

N rated tires are listed as temporary spares. Surely nothing you want to run on your truck.