Rear axle width

[chopthebass]

I have a quesiton relating to the rear end. My planned build will have a live rear axle and 3-link set up.

I'm not too knowledgable about the whole rear end and need to determine what changes (if any) I need to make in order to use 315/45-17 tires. I see some pics of builds where the tires are set in from the wheel arch and this could be a narrower tire width or could it ba a narrower axle? I don't like this look. It looks too narrow for the car.

Basically I am looking for the rear to look wide and tough! So I want the wheels to fill the arches, if you know what I mean.

Cheers
Ian

[Cobradavid]

Ian,

I have 315/35-17 tires on 17X11" wheels (with 8.75" backspacing) on the rear. My rear axle and front spindles are from a 2001 GT (SN-95) and I have the FFR 3-link. I don't recall the width of the SN-95 axle, but maybe someone here will have a number for you.

I think I put 1/4" spacers behind my wheels to move them out just a tad. You can see photos on my website (link in my signature).

David

[chopthebass]

Thanks David. Useful info.
I didn't know you could get 17 x 11" hallibrands replicas. I've only seen 10".
So can you buy spacers of varying width?
Also what does 'backspacing' mean?

[Cobradavid]

Ian,

I bought the Team III wheels from FFR when I ordered my kit (in 2008).

You can get wheel spacers in different widths. If you use spacers, make sure your lug studs are long enough to get good engagement on the lug nuts. However, if you're shopping for wheels, just get the backspacing you want and don't mess with spacers. For example, I could use a wheel with 8.5" backspace instead of my 8.75" wheels with 1/4" spacers.

Backspacing is the measurement from the wheel's mounting face to the wheel's inner lip. There's a good graphic on this site:
http://www.rimsntires.com/specs.jsp
Note that there's also "offset" which measures the wheel mounting face relative to the centerline of the wheel/tire.

Hope this helps!
David

[chopthebass]

Thanks David,

I checked out the calculator you sent, and put in the tire size, but it didn't show 8.5 or 8.75" anywhere. How did you decide the backspace you needed?

[chopthebass]

I guess what I am trying to get my head around is this..

When I buy my rear axle and get it on the car, how do I work out the best backspace to give a good stance. Ordering the wrong wheels will be a costly mistake!

Cheers

[Cobradavid]

The wheels I bought were the size that FFR suggested, based on my SN-95 donor components. To be honest, I didn't do much research before I purchased. I didn't know about these forums until after I was already in the build process. So basically, someone else decided what backspacing I needed :)

There's no backspacing input on the calculator, you have to put the offset in the "ET" field. I think that's in mm, and you can play with different numbers to get the right amount of backspace to show up in the graphic. I just now tried it and put in 64 for the off-set. That gave me a 8.5" backspacing on a 315/35 17x11 wheel.

Here are links to wheel and tire specs on this forum.
http://thefactoryfiveforum.com/content.php?203-Wheel-Tire-Specifications-Roadster
http://thefactoryfiveforum.com/showthread.php?1869-Wheel-amp-Tire-Specifications-Roadsters-and-Type-65-Coupes
http://thefactoryfiveforum.com/showthread.php?1869-Wheel-amp-Tire-Specifications-Roadsters-and-Type-65-Coupes&p=19123#post19123

I think all three posts have the same data. You can see that the different years mustangs had different widths, with the wider axles being the newer ones. Maybe some of the super-knowledgeable folks like Mad Dog, JKleiner or someone else can jump in with more information.

One way to work out the best backspace is exactly what you're doing! Ask folks what set up they have (what axle width, what wheels) and decide if you like how theirs looks.

Or you could buy one of these: http://wheelworksinc.com/ Hey, it's only money, right? ;)

David

[Gordon Levy]

my 17x11 rear wheels used a 6.75" backspace on a Fox width rear and a 7" backspace on a 94-98 rear. For me the 99-04 housing is just to wide to work well.

[CraigS]

To make this as easy to deal with as possible just make sure you end up w/ a Fox width rear axle assembly. that is the narrowest of all the Mustang axles and allows the widest wheels at reasonable prices. The easiest and least expensive is a Fox axle and these wheels or the many others available in the same dimensions.
http://www.americanmuscle.com/dedibuwh.html
Notice they are listed as 99-04 but click on the 'specs' button and see the backspace and the offset. I don't pay any attention to offset because I can't measure it. Backspace is easy to understand and measure. You just lay the wheel nice side down on the floor, measure from the surface that mates to the axle up to a pieces of anything straight layed across the wheel edges. That is B.S. except for the material thickness. See here
http://www.youtube.com/watch?v=n96lE8jdMlQ
If you look through American Muscle in the 1994-1998 section you will see a good selection of 10.5 x17 wheels. just verify the B.S. is 6.8" and they will fit fine w/ 315 tires. Other brand wheels may show B.S. of 6.8 to 7.0 and they will be fine also.

[chopthebass]

Thanks Gordon & Craig. Excellent info. I understand fully now.