Need help understanding backside, offset, etc.

Hello everyone.

I need a little help understanding wheel backside, offset, etc. I *think* I pretty much get the gist of it, but hope someone here can indulge a newbie and explain a few things.

I have a Jeep Wrangler TJ (1999). I've installed a 4" lift and upgraded to 33" tires. When I made these upgrades, I also bought new wheels. They are American Racing Diamond Lock, size 15x8. Offset is -19 and Backside is 3 3/4.

I'd now like to switch out my wheels for American Racing Chamber, size 16x8. These come with a zero Offset, while Backside is 4 1/2. I'll probably stick with 33x12.5 tires, upgrading from AT to MT.

When I first installed the Diamond Lock wheels, they definitely stuck out farther than the Jeep factory wheels, a good thing considering the increase in tire size. How do Offset and Backside dictate how a wheel will behave? From my understanding, Backside determines how far out the wheel will stick? But what about Offset?

If I go from a wheel with a negative offset (the Diamond Lock) to one with a zero offset (Chamber) and greater backside (4 1/2 vs. 3 3/4), will this wheel stick out farther? I guess I'm just trying to understand how offset fits in. I understand that it is measured from the center of the wheel to where the wheel mounts. Does offset determine backside?

Thanks in advance to anyone who can explain this. :-)

-Rob

Hope this site explains

http://www.comp.co.uk/techinfo/techinfo1.htm#

US site may be more helpful

http://www.usacomp.com/terms.htm