tire size

[kens65fb]

I'm working on a 57 Ranchero restomod, the vehicle came with 1991 Mercury Grand Marquis Alloy Wheels that measure 15 X 6.5 with 4 7/8 backspace; tires are 215/70/15
I spoke with a wheel vendor at the fall Carlisle swap meet last week, and he recommended 17X7 front , and either 18x7 or 18x8 rear wheel

Front   -----  235/45/17 on 17X7 wheel  with   4.50 backspace

Rear    -----  245/45/18 on  18x7 wheel          4.50 backspace
                            OR     
                   255/45/18 on  18x8 wheel          4.50 backspace 

He seemed very knowledgeable, and was not trying to push a sale at all.
Any comments on fitment??--Or any suggestions on sizing??
Thanks

[Bubba]

Check the tire and wheel sections there are tons of threads on this topic.
Some written by Ranchero owners.  Most of the wheel sizes discussed are however 15 inch diameter with a 7 to 8 inch width.  I haven't tried it yet but the experts on this web site say a 4.5 inch back space for the rear wheels is the minimum requirement if you want to run a modern wider tire.
BuBBa

[57chero]

kens65fb, I replied to your question in the (Wheel and tire sizes) section.