A friend of mine has a 2007 regular cab short bed 1500.

He wants to go down to a 17" rim. The stock rims are 20", and from what I've read on here, are 5.75" backspacing...So he would want, say, a 17x9 with 5.75" backspacing to keep a similar tire size. Correct?

 

Well I mean he can't really keep the same size since he's going from 20 to 17. But number wise he can get close with a 285/70/17. It will be a slightly wider tire but that's the best you can do. Most 17s that are aftermarket come with a variety of backspacings and offsets though so he can pick wheels accordingly to how wide or narrow he wants his tires

 

The same backspacing should allow for a similar width tire should have the same profile appearance in relation to the fenders as far as sticking out or not. It's not really related to the height of the tire. If he wants to go with a wider tire, he should get some rims with less backspacing and some negative offset. But that will cause the tires to extend out past the fender a little bit in order to not crowd things up under the fender too much and cause rubbing. For example, see my sig pic. 17's with -12mm offset/4.5" backspace to accomodate the 305/70/17 tires. If considering going up much in overall height of the tires, he should also consider leveling the front.

 

???huh???



if he wants the tires to jut outward from the wheel well, he'll want negative offset- that pushes the dish of the wheel further toward the hub, making the wheel push outward outside of the wells..

if he wants a more narrow stance, he'll want positive offset, which makes the mounting surface of the wheel closer to the front (decorated side of the wheel, so to speak) of the wheel..

the width, he'll want likely at least 9".. that gives you a decent margin of tire sizes to work with..

backspacing, stick with the stock at the least- 4.5" .. you gotta clear those calipers, yo!!