what is offset and backspacing??

[BIRD67]

Okay, I know it isn't a Mopar, but currently our Firebird runs on a set of original (cast 1967) Cragar S/S wheels.. I know that they measure up to be 15x7 and we run a rather small 215/65/R15 Tire.. My question is, what is offset? Is it how deep the wheel's outer rim is? I like the really deep look on rear wheels but I cannot figure out what the right offset would be.. I have seen Charger projects on here like Moparstuart's Daytona clone that have the nice deep rear wheels like I want, and I asked him on his thread but I got no response.. Also, what is Backspacing?? I think I need serious help in the wheel department!!

[lisiecki1]

offset and backspacing go hand in hand....negative offset=less backspacing, positive offset=more backspacing....here's a couple diagrams:



this is negative offset



this is 0 offset, which shows you how positive offset is

these were pulled from this web address: http://www.chevellestuff.com/tech/wheel_offset.htm

[bull]

The only measurement you need to worry about when ordering is backspacing (from the back of the hub to the back edge of the rim). Don't confuse yourself with too much info.