Wheel/ tire widths with SN95 donor

[WarDamnEagle]

I am building a donor build with the donor lower control arms and rear end from 99 mustang GT. From what I can tell the factory wheels are 17x8's with 5.75" backspace. And the tires appear to clear the control arms at full turn with plenty of room to spare. It is time to order some tires and wheels, and the build manual says I cannot run wheels wider than 7" without the FFR lower control arms without having the wheel rub the control arms. Obviously that is not the case since I have the 8's on there now. Could this be another missed update for the build manual that never evolved from the FOX spindles? Does any body know if I can run 18x9's with 6.2" back space?

What is the interference issue, the control arms or the wheel well?

Thanks for any help

[CraigS]

The interference is on the front lower edge of the control arm. The front surface of the arm is vertical w/ an outward turning flange at the bottom. That flange edge contacts the wheel at the inside just below the lip.
https://farm1.staticflickr.com/944/41467224954_58b28899fc_z.jpg (https://flic.kr/p/26bjnho)wheel_diagram_2 (https://flic.kr/p/26bjnho) by craig stuard (https://www.flickr.com/photos/152454123@N04/), on Flickr
the red arrow is where my 9x17s (6.0 BS) hit on my OE arms long ago. I would think 18s might give a little more room but the extra .2 BS would make it a little worse. Back in the day the wheels were either re-shaped a little w/ a sledge or ground a little. I ground mine

[Mustang Man]

You could add more steering limiter C-clips to the rack to prevent them from touching the arm, albeit at the cost of less turning radius. Honestly '99 and up is not the best to use for front spindles and rear axle. It pushes the wheels out. Best to use is '94/'95 spindles (same offset as Fox) and the '98 on down rear axle (with Fox length axles in it)...

HTH...
Mark

[Jeff Kleiner]

As Mark indicated '96 and later spindles set the wheel & tire out farther which in addition to the issues with the lower control arms can result in tire to body interference depending on the wheel & tires that are used. Similarly and also as Mark mentioned the '99 rear end is wider and can not be brought to the generally preferred Fox width without cutting the housing and changing axles. Although these components can be used there are some limitations and they require you to be very cautious/well informed when selecting a wheel and tire combination.

Good luck,
Jeff

[WarDamnEagle]

You guys are such a wealth of knowledge, I love having this resource.

Thanks for the detail Kleiner, Now I'm going to go for broke and ask about narrowing the track width of the rear end. I am not using the ABS. I am comfortable fabricating my own new caliper brackets, so can I simply put 93-93 or even fox body shafts in my axel housing without having to cut the housing? (there is about 1.75" from the seal to the back of my wheel studs)

[JRD56]

Another benefit to 94/95 spindles is reduced bump steer. I just finished a build where I initially installed 2000 GT spindles but was not happy with the amount of bump steer I had. So I switched to 95 spindles and was able to reduce the bump steer to almost zero. You can retain the SPD brake calipers with a little grinding on the 94/95 spindles. I do have additional steering limiters in the rack, but I haven't noticed any issues with reduced turning radius either on the street or doing Autocross.

Jim

[Jeff Kleiner]

Thanks for the detail Kleiner, Now I'm going to go for broke and ask about narrowing the track width of the rear end. I am not using the ABS. I am comfortable fabricating my own new caliper brackets, so can I simply put 93-93 or even fox body shafts in my axel housing without having to cut the housing? (there is about 1.75" from the seal to the back of my wheel studs)

No, you can not and that's the problem. SN95 housings from 1994 through 1998 are actually the same as Fox but with longer axle shafts which have all of the additional length outside of the housing beyond the seal. With these you can simply swap to Fox length axle shafts and move the calipers in. The 1999 and newer rear ends have wider housings---you can't put in the shorter axle shafts without cutting and narrowing the housing. Your options; 1) Pony up the money to have the housing narrowed and fitted with new axle shafts. 2) Go to non-standard custom offset wheels and use what you have...note that this will not allow you to have any sort of "deep dish" to the rims. 3) Pick up an earlier rear end that can be brought to Fox width by changing axles and fitting it with caliper relocation brackets. #1 and #2 will probably be near the same $$$ in the end; #3 should be the least costly.

Jeff

[Norm B]

I have a 95 front end in my car with the Mustang lower control arms. I have the 17 inch Halibrand replica wheels from FFR. With this set up the rear inside of the tire contacted the F panel before the wheel hit the control arm at the front. I installed 12mm rack limiters and stopped the possibility of either happening.

HTH

Norm

PS. Make sure to check for wheel clearance at the top of suspension travel at full lock.