Recently picked up a 65 skylark. Want to switch out the stock 14" tires for some 15"s After much searching and researching I'm still wondering what is the biggest tire I can fit in the rear with a 15x8 Buick rally with the 4.5" back spacing? I know I could get a 275/60/15 on a 5" backspace. But what about on the 4.5? 255/60/15 maybe? The car is all stock with the stock rear end. I'm thinking 225/60/15 on a 7" wheel in the front.
A stock 15x7 Buick rally with 4-3/8" backspace will allow a 255/60/15. It's a little tight on a '66 but they say the '65 has a little more room at the fender lip. I believe there were couple 65 guys that even ran 275's. So the 255 on your 15x8 should work too, but it'll be 3/8" further outward than the above combo. Backspace is usually measured to the edge of the wheel lip, not to the tire seal surface. So a 15x7 is actually 8" wide edge-edge, and a 15x8 is 9" wide. Your 4.5" back space means there is 4.5" frontspace..... or to use the other term, zero offset. The 15x7 is 4-3/8" backspace and 3-5/8" frontspace, or 3/8" offset. I made up the term 'frontspace', but you should know what I mean.... I run 235/60-15's on the front of my 66's. 225's would be on the small side. 215/65-15 is another option. Here's a tire size comparison calculator: https://www.tacomaworld.com/tirecalc?tires=225-60r15-215-65r15
Bill, The rears on my car now are P235/70R-15, the fronts are P215/70R-15's. I still have the original coils in the car, but I have new Moog springs ready to install (when I have the time). My rears were a little sung and I had to raise the rear at the frame and put the top of the wheel/tire in first to get them on. I haven't experienced any rubbing front or rear. I'm curious to see the stance with the new springs and this wheel/tire combo. Doug
