I have a 69 Cutlass S Holiday Coupe and I am going to upgrade the stock 14 inch rally wheels. I'm wanting to go staggered wheels in 17 or 18 inch wheels. I don't understand how to measure for offset or how it works so any information would be helpful. Thanks in advance.

 

 

As Ralph's diagram notes, backspacing is a relatively worthless dimension, since it depends not only on rim width but also the thickness of the lip. Offset is what matters but that is more difficult to determine, which is why all the wheel vendors list backspacing. Of course, the wheel is only part of the equation. Tire outside diameter and width are obviously very important, as is ride height (is the car at stock height or lowered?). I've run 255/60-15s on the stock 15x7 wheels on my 69 H/O with only minor rubbing at the front when hitting a bump with the wheels turned hard. These are 27.05" outside diameter and 10.04" section width. Stock tires on a 1969 Cutlass were F78x14, which were 26.50" OD and 7.90" section. Cutlass wagon ran slightly taller G78x14s with 27.05" OD and 8.35" section. I just went with 245/60-15s for my 69 flattop, which are 26.57" OD and 9.65" section. If you want to run staggered sized, you can go quite a bit wider at the back.

255/50-17s are the same OD and width as my 255/60-15s and will likely rub a little in the front. 245/45-18s are virtually identical to my 245/60-15s and should be fine in the front.