RodnReel

Okay Forum, I've read a lot of information about purchasing aftermarket wheels - However, I'm unclear if there is a difference in purchasing a wheel with a zero (0) offset, vs one with a positive or negative number, with regard to maintaining 4 inch backspace requirement for a proper fit, i.e. original rally 15X8 wheels. I see some reports who mention a negative twelve (-12) offset in conjunction with the 4" backspace for a proper fit on a 1973 Ray...Guidance?

69autoXr

Offset and backspacing are two methods of measuring basically the same thing, the position of the wheel mounting flange, relative to either to the inner flange (backspace) or wheel centerline (offset). That said, neither can be changed without the other changing as well (assuming equal width wheels).

See this page for technical explanations: https://rsracing.com/TechWheel.aspx#backspace

A 15x8" wheel with 4" backspace has an offset of -12 mm.

Cryptoboy

Also, do you have any thoughts on what size and width wheels you want? I think that will help if you have that baseline to start with.

I ended up getting US Mags 17" front and 18" rear wheels for my 74, with a 4.5" offset in the rear (18x8).

RodnReel

Thanks for the info, but I think I'm staying with the 15X8's - at least for now...appreciate you sharing...

V/R

Rob

george2066

top of c3 tech forum, look at the pics for 15, 17 and 18 tires and rims