Hi Dave,  Welcome to FYIFord!  Since I am NOT one of the many engineer folks that frequent here, I cannot figure out things three steps ahead.  My tendency would be to get the front and rear ends of choice mocked up, hang the rotors and calipers, and then measure what you actually have to determine the perfect wheel fitment, prior to ordering custom wheels.  There is a lot of experience here, and there will be lots of help when it comes to spending your money

JeffK, having less backspacing moves the wheel outward, not inward, or maybe I misunderstood your statement.

The best handling will be achieved with a 17x7 with 4" backspacing, which is a zero offset wheel like the car was designed to use.  This plays heavily into handling and scrub radius.

Best fender clearance compromise is to use a 4.25" backspacing.  The scrub radius won't notice 1/8" difference from center.  At least not much.

I do not see how a 17x8 wheel with 4.5" backspacing and a 245x45/17 tire would clear the rear quarters.  A 17x8 with 5.72" backspacing and 245x45 tire (same wheel as Bullitt Mustang 2002) seems to fit the rear of a 65/66 just about perfect.  At least it did on my car and on the 65 couple I did for a customer recently.  A wheel with 4.5" backspacing would stick out 1.25" MORE and would surely rub the quarter no matter how much you rolled the lip, as least on those two cars.  For that to clear, it seems like the rear of the car would have to be lifted up way high and have some positive stop to keep it from ever approaching the stock ride height.  I firmly believe a tire needs to have 100% clearance at any point in the suspension's travel limits.  It will, at SOME POINT, use all of the available travel, even if it doesn't rub when carefully driving down to Sonic.

A 17x8 wheel with 4.5" backspacing is a lot easier to come by than a wheel with deeper backspacing (that has a matching front wheel in 17x7), so I am open to being educated as to how to make that work.

I am having a custom width rear made for my 66 right now to work with the 17x8/5.72" backspacing wheels and 245x45/17 tires.  The total width of the rear is 58.25" from axle flange to axle flange.  Calculations show this is the perfect width to get the rear wheels under the quarters without rubbing, and provide maximum width possible.  I verified this dimension with the old rear end by installing spacers to make the rear end think it was 58.25" wide.
Clearancing of any sharp edges on the inner wheel house is recommended just in case the tire rubs on a sharp inclined driveway.  They will not rub at any other time,and you are going super slow when it happens, if ever.

Last edited by MS (4/19/2016 6:31 PM)

Yep, I can see that probably would rub in the rear if you bottomed out the suspension.

Sorry please disregard the last comment on the last post - I see my error - small difference in tire diameter on a 245/45/17 with a 17x8 wheel and 235/45/17 on the 17x7 wheel in the front. Typed an 18" diameter rim into the tire comp app I had. My bad ....

Hello I own a 1965 Ford Mustang C-Code Coupe 289 C4 Automatic factory A/c And Factory P/S.  I went with 1" lowering coil springs from Eibach also plan on doing shelby drop. For my wheel Tires combo I went with a 17x7  front and a 17x8 rear. Believe the fronts are 4.25" backspacing  and rear 17x8 are 4.5 backspacing. Tires are 235/45 Z R 17 for front. and for the rear wheels I went with tire size
245/45 Z R 17. Purchased wheels on Ebay MS actually hinted me in the direction as he was telling me about his Bullitt wheels that he had been custom made to his specs. I found the set of wheels listed for 65-73 Ford Mustangs. Beleive the Wheel Is called a Retro.

Last edited by True74yamaha (5/27/2022 4:04 PM)

Looks very nice.