As an added note, 1967 to 1973 Mustangs have much larger fender openings so tire rubbing is a lot less of a problem. But, too much back spacing can allow tires to rub on the frame when turning, especially when parking. This can be worse than rubbing on the outside of the tire because you can be totally unaware of a rubbing problem until you have ruined a tire. Be sure to check the tire to frame clearance if you use a wheel with a lot of back spacing.
|The first place your rear tire will rub in the rear is not on the leaf spring. It will first rub on the front inside inner wheel housing that is shown here. This is a sharp edge that can be bent inward to clear the inside edge of the rear tire. But don't get to wild with those 5 pound hammers!|
|Measuring the back spacing on any wheel can be accomplished by laying a straight edge across the wheel and measuring down to the surface that bolts to the brake drum or brake rotor. This 17" x 8" wheel has a 4 3/4" back space.|
On the rear of our little ponies, most of us look at the rear leaf springs and see that there is a lot of distance between them and the tire. So we assume that a wider tire and wheel will fit. But the leaf spring is not what will interfere with the tire first. The first place your rear tires will rub is on the front inside inner fender wheel well housing. Be sure to check this area for rubbing when using wheels with a lot of back spacing. The second place is on the back of the wheel well housing. Also, when changing from drum to disc brakes in the rear, remember that the brake drum you're taking off the car will be thinner than the brake rotor that you're putting on the car. This will move the rear tires just that much closer to the rear fender lips so you could have some tire rub where you had none before. Remember, I said that you could have some tire rub, not that you will.