When replacing the stock rearend with a 12 bolt, has anyone had the rearend narrowed on both sides??? It appears that there is room for approx 2-3 inches of space space the inside of the tire and the inner wheel.

 

Buy a 12-bolt for a 3rd Gen, with the 4th Gen disc brake mounts. It will be 3" narrower (1.5" on each side) than the 4th Gen rear axle assembly. Otherwise, everything is the same.

 

My real question is this: By narrowing the 12 bolt housing a total of 2-3 inches, is there any advantage when it comes to fitting max size wheels and tires under the car? (forth gen.) ie. a 10' or 11" wheel with a 10.5" or 11.5" slick or a 315 street tire? Would the narrower housing and axles allow the bigger wheel and tire combinations to fit in the wheel opening without having to modify the lip? Or are there other clearance issues that have to be dealt with?

 

It would only allow for diffrent offsets in the wheels. Instead of running a 7.5in bs wheel you could run a 6in backspacing wheel. Go 2 on each side for a total of 4in shorter, you can run a 5.5in backspacing wheel. Then you have a bit more of a variety of wheels to choose from, not to mention a bit cheaper pricing on wheels. More of a cosmetic thing seems like.

Kyle

 

The reason I am asking is that I am about to order a 12 bolt and was looking at another '96 f-body with 28x15x10.5 wide slicks using a standard width 12 bolt and there was approx. 3 inches of additional spacing between the inside sidewall of the tire and the inside of the wheelwell. The tires that were on the car were not sticking out past the lip of the wheelwell opening, but they were very close. From what I have read, it appears most people that run max size tires seem to have an interference issue causing them to have to modify the lip in order for the tire to fit. It is my thinking that if the housing is approx 1-1/2" to 2" narrower on both sides, the clearence problem would be eliminated. Has anyone done this??? If so, did it achieve the results you wanted???

 

Sounds like they have the wrong backspacing. You can do what you want, without changing the rear end width. Just get a set of wheels with the correct backspacing and you will be good to go. I had a set of 15x10in ProStars with 28x11.5 hoosier QTPs, with 7.5in of backspacing they sat as far in as a set of stock 16in wheels would have. NOWHERE near rubbing the fender lip.

Kyle

 

You're confused.... there is a fixed width available between the fender lip and the inner fender liner. That space can not be changed, except by a body shop, with a torch and a Sawz-all. Altering the width of the rear axle assembly will not change the physical space available for the tire. It will only alter the wheel offset required to place the tire correctly within the available space, so it doesn't rub.

I run 28" slicks. With a set of 28x11.5-15 QTP's, they fit correctly in the wheel well, and did not rub on the fender lip or the inner fender liner (although that had already been hammered a bit for 315's on 17x11's). The rear axle did have to be moved back about 1/4" to prevent the tires from rubbing on the front sheet metal of the wheel opening, when trap speeds went over 120-125mph.

You want a 15x10" wheel, with a 7.5" backspace, with the stock 4th Gen rear axle dimensions. As noted, if you went to a rear axle assembly that was 2" narrower on each side, you would buy the same wheels with a 5.5" backspace. The wheel/tire would remain in the same place in the wheel well.

Not all 15x10 wheels are made with a 7.5" BS. If, for example you wanted to use the CenterLine Convo-Pros, you would have to get a narrower rear axle, since they are not made in a 7.5" BS.... I think 5" is the largest.