Hi,
I need help. My '04 Supercrew came with a tire size of 255 70 17 which is a General Ameritrak tire. There are no other tires on the market in this size except this particular manufacturer. Obviously, if I up-size the tire there are more choices available. Will putting a larger tire on the vehilce affect any mechanical functions i.e., 4*4 service , transmission, ABS etc. ? Please advise.

 

Depending on how much larger you are wanting to go, you shouldnt need to worry about those things.

Larger tires will make your speedo show you moving slower than you really are, so be aware of that. You'll need to reprogram your computer to compensate, and you have several options:
take it to dealer (probably going to rip you off)
buy a tuner...most will allow you to input tire size

 

I went from a stock 30 inch tire to a 33 inch tire. The only problem I have is my spedometer is off 5 mph at 60 mph. You don't have anything to worry about.