Do you know by how much?

 

i just put 15's on my 01 and didnt have to do anything they fit perfect no rubbing the caliper at all. it all depends on the wheel and the manufacturer.

 

I'm a bit uncomfortable running a 15 inch wheel even if it would fit and here's the main reason
The dual piston brakes were incorporated into the Ram so that there would be an increase in stopping power and a decrease in stopping disctance. Even so, they generate a lot of heat when being used, and always seem a heartbeat away from fading.
Going to a smaller wheel also decreases the cooling area surrounding the caliper/rotor which could induce quicker fade or failure. It's your ram, but saving a dime and ending up spending a dollar isn't solid logic
Also, even if the wheel fits, placing stickon weights in the wrong spot could lead to interference. Hacking at your brake caliper with a hand grinder will at the least ruin your core value on a rebuild (about 55.00).
Pay the 2 bucks...and do it right.

 

Thanks Dsertdog

 

well i have an update for you. my 15's run great. but if youre going to put anything on bigger than a 32/33 rear gear your axles. my truck runs fine until its been running for a while then if you push the gas pedal down any more than 1/4 throttle the trans starts to slip from overheating do to the larger tires. my 265/75/16's are going back on either today or tomorrow.