10-Ford

Hmmm, I guess I learned my something new for today. I know that offset is measured to the outside lip of the wheel and that backspace is measured to the inside of the lip (which I always thought was ridiculous). If the two were based on the same measurements they could be easily calculated.
But I've always assumed the wheel width was the measurement at the widest point (outside lip to outside lip).
Thanks for clearing that up.

techrep

iTrader: (1)

The wheel Gods have spoke.....

jklew

This is a cool tool I stumbled across in my hunt for wheels.

http://www.rimsntires.com/specs.jsp

This is what I am considering. Raceline Raptor. It comes in an 18x9 with +25 offset. Thinking of wrapping them in a 33x 12.5 or 11.5 Mickey Thompson ATZ.

FX4ord

Offset is measured from dead center of the wheel (width). Positive is toward the outside, negative is toward the vehicle. Backspace is the true physical distance from back of mounting plate to outer edge of inside lip.

That is correct. However, an 8" wide wheel is physically 9" wide because of the 1/2" bead lip on both sides, though it's called an 8" wheel. Just like a "2x4" piece of lumber isn't a true 2" x 4". A 9" wheel = 10", and so forth.

Offset and backspace, fortunately, are precise physical measurements that require the lips to be calculated in when wheels are designed to fit specific vehicles. So, the 1/2" lip is part of the total backspace measurement listed for all wheels.

dshale10

I've been trying to figure out this whole idea about back spacing/offset. Apparently, I'm a rim/tire illiterate lol caus ei keep getting more and more confused. I'm looking at getting a 4" rough country lift installed on a 2011 screw fx4. I was trying to figure out a good size rim/tire combo so I won't be stuck driving stock set up. I'm looking at 18" rims an either 35' or 325 (not sure exactly that size). I want the tires to stick out a little outside the fender flares, but not too much, and i don't want a alot of fender wheel space. I will eventually add some 1.5 buswhacker fender flares so figured tires should be at least as wide or a hair wider than flares. Any help would be appreciated. I'll probably purchased rims/tire combo on line an will need as much info as possible. Also, hope to trim none or at the most very little.

LMychajluk

dshale - Look at the calculator I posted back on page 1. That will give you an idea of how much the wheel will stick out.

Since the tire will be wider than the wheel, subtract your wheel width + 1/2" from the width of the tire (specs can be found at TireRack.com or the tire manufactur's site), then divide by 2 and add that to the results of the calculator to figure out how much your tire will stick out.