Since its inception in 1964, the Mustang formula has always been about cheap, fast power combined with muscular styling. The Fox-body Mustang delivers in both these areas, much like the classic muscle of the '60s and '70s. Fox cars are easy to work on, and it doesn't take much to make them an all-out street terror.
But like classic muscle, when it comes time to slowin' things down, this is also a weak point for the venerable Fox-body Mustang. We've known this for years, and have found many solutions to the Fox brake problem. Of course you can go the big-buck route, but that doesn't always suit the majority of owners. So, as you'll see, we found a better way to improve braking with out breaking the bank.
For this install we utilized a Scarlet Red '88 Mustang GT five-speed hatchback. The author purchased this car a year ago for just $3,800 and with only 97,000 original miles on the clock. Other than the ram-air hood, it was bone stock, clean, and solid.
After about a year of driving 60 miles a day on a 20-year-old suspension and with anemic brakes, I knew it was time to do something. The brakes were in need of replacement and after a lot of research and consideration, I decided that an affordable way to upgrade the brakes on the Fox body was an SN-95 disc brake conversion.
The SN-95 conversion is a great way to upgrade the braking capability of any Fox body. And, since we'll be ditching the 4-lug wheels for a 5-lug setup, wheel choices will be almost endless. For daily driving duties, I picked up a new set of 17x8 Bullitt wheels, along with a set of used, but almost new 17-inch Z-rated tires totaling up to only $550.
Like every Mustang I own, this Fox will eventually find its way to a dragstrip for some straight-line fun. Although I'm leaning towards the handling direction with this '88 GT, a good set of skinnies and some fat tires out back always helps to knock a few tenths off. In addition, Mustangs look really wicked with "big and little" tires mounted up.
I wanted something a little different than what most guys had on their Stangs, and when I saw the new Billet Specialties Street Lite wheels, I knew right away they'd do the trick. Designed for the street or strip, the Street Lite wheels are SFI 15-1 approved, lightweight, and features an outstanding strength-to-weight ratio.
These 15-inch Street Lites are absolutely gorgeous and combine a polished and machined finish for an aggressive look. Sizes range from 15x3.5 to 15x15, and they accept mag shank lug nuts and can be used with 5?8-inch racing studs.
Now that I have a nice set of drag wheels, I'm going to need some tires to make things stick out back. I decided go with a set of Nitto 555R drag radials since this car needs to be streetable, and I want to keep my stock 8.8 rearend in one piece. I've consistently dropped as much as three-tenths of a second in the quarter-mile and improved 60-foot times by as much as two-tenths on a couple stock 5.0 Mustangs. Not bad for a street tire that I got 15,000 miles out of along with a few burnouts at the strip.
Before you drop a lot of money on wheels and tires, you need to measure twice and spend once. If you're like me, you want to get the widest possible wheels and tires on your Fox-body. especially out back. The North Race Cars Fox-Length Rear Axle Kit is just the ticket. You can order the complete rear axle kit, which includes the Fox-length axles, laser-cut caliper brackets, bracket bolts, new e-brake cables, and rear brake line fittings. These parts are also offered separately. What's great about this kit is it will fit most popular aftermarket and OEM 9-inch-wide rear wheels, and a 275-width tire inside the rear fenderwells with no clearance issues at the wheelwell lip, unlike the stock SN-95 rear axles which pushes the track width out about a -inch further on each side.
To get the project started,...
To get the project started, we got the Mustang up in the air and removed the wheels and tires. We also removed the brake drums and shoes, and the parking brake cables.
Now you'll want to remove...
Now you'll want to remove the driveshaft to get access to the e-brake cables on the other end.
Remove the master bolt from...
Remove the master bolt from the rubber line to disconnect the brake hose from the brake line. Tip: A 12mm socket will be needed here.
Now you'll want to remove...
Now you'll want to remove the quad shocks and rear sway bar.
Next you'll want to remove...
Next you'll want to remove the rear shocks. Tip: After removing the nut, leave the shocks on the mounting bolt to hold the rearend and suspension in place.
Before we were ready to remove...
Before we were ready to remove the rear axle assembly, we used a transmission jack to support the rear while we disconnected the rest of the rear suspension. Now the bolts can be removed from the shocks and the rearend assembly can be lowered down.
Then we bolted on the North...
Then we bolted on the North Race Cars rear caliper brackets, bracket spacers, and dust shields. Note: Left and righthand moan braces are optional at this point. Some cars may need them and some may not. I didn't install them on my car, and so far have had no issues with any rearend moan. These should come with your rear disc brake swap kit, or you can order them new through Ford (Moan Brace R.R. PN F4ZZ-2C366A, and L.R. PN F4ZZ-2C367A).
At this time, I decided to...
At this time, I decided to replace the worn out stock 8.8 rearend assembly with a new one from Ford Racing complete with 3.73 gears. NOTE: For our conversion, we purchased the Fox-length axle kit and e-brake cable kit from North Race Cars. To use the Fox-length axles, you'll need to use the custom rear caliper brackets from North Race Cars. This kit allows you to retain the stock Fox-body length axles, which gives us more options for running wider rear wheels and tires. I highly recommend purchasing this kit.
The rear brake lines that...
The rear brake lines that used to be routed to the drum brakes are not compatible with the newer SN-95 rear calipers. John Scatterday fabricated a custom rear brake line using 3/16-inch hard line and a flare tool kit. He reused the center Fox-body brake line junction and the brake line fittings to the SN-95 rear calipers. The length needed for the passenger side brake line should be approximately 32 inches long, and the driver side should be about 30 inches long.
Wheel And Tire
Installation And Fitment Notes
Billet Specialties Street Lite Wheel and Tire Combo SpecificationsFront
Wheels: 15x3, 1.75-inch backspacing
Tires: Kumho Power Star 758 165/80-15
Notes: For front caliper clearance, I used a Mr. gasket 7/16-inch wheel spacer and needed to clearance the caliper bracket about 1-2mm only on the outer surface to make sure there was ample clearance for the caliper bracket behind the wheel spokes. Since I used the 96-up front spindles, the 7/16-inch front spacer, and 1.75-inch backspacing pushed the front wheels and tires out just inside the front fender lip. Since my car is lowered about 1.7-inches, the front tires are just inside the lip and fit is a little tight, but safe. For Mustangs with stock ride height to moderate lowering, this combination will work just fine. For improved wheel-and-tire clearance, I recommend '94-'95 SN-95 front spindles. They bring the front wheels and tires in about 3/8-inch each side, and if you use a 1/2-inch spacer, the front skinnies will tuck under a little more with ample clearance.
Rear
Wheels: 15x8, with 5.5-inch backspacing
Tires: Nitto 555R Drag Radials 275/50-15
Notes: Again, since my car is lowered about 1.75-inches, there's minimal clearance issues, but I've put almost 200 miles on this setup and had no safety issues. I had no tire scrub issues on the driver side tire, and very minimal scrub on the very edge of the tire sidewall but no tire damage. Some cars may vary, but when plus sizing wheels and tires, some modifications may be necessary such as rolling the lip for optimum clearance. I've had no inner fenderwell clearance issues with this wheel and tire combo.
OEM Ford 17-inch Bullitt Wheel and Tire Combo Specifications
Front And Rear
Wheels: 17x8, 5.65-inches backspacing
Tires: 245/45ZR17
Notes: With the '96-'04 front spindles and the 1.75-inches suspension drop, the tire clearance up front is tight. There's little to no scrub up front. I have ordered a set of stiffer struts and shocks which will help tighten up the front suspension and reduce wheel jounce, which should eliminate any front tire scrub. I can also clearance the fender lip a little more if necessary. Since I went with the North Race Cars Fox-Length Rear Axle Kit instead of the SN-95 rear axles, I have test fitted 17x9 OEM wheels out back with a 5.97-inch backspacing and 275/40ZR17 tires with no clearance issues. I will clearance the rear fender lips some for added insurance.
Other Modifications Made During Installation
- Eibach Sportline Springs: 1.5-inch front drop and 1.7-inch rear drop
- Eibach Front and Rear Sway Bar kit
- Aftermarket upper and lower control arms
- New FRPP 8.8 Rear End Assembly with 3.73 rear gear ratio
Modifying Your Fox-Body Emergency Brake
You're going to have to make some minor modifications to the e-brake on your fox body so that it works correctly with your SN-95 rear calipers. The mission of ratcheting mechanism on the stock handle is to adjust the e-brake. It does this by placing tension on the cables and ratcheting up a tooth at a time. This function needs to be disabled with disc brakes.
There are two options, one is unwind the spring and hope the spike lines up with the ratchet every time. By far the most common is to push the handle down and manually unwind the spring about a 1/2 inch, then pin the handle with a bolt. This makes the handle non-adjusting but still pulls on the cables. This can be done with a bolt, a nail, or a zip tie. The key is to take spring pressure off of the cables. If the spring pressure on the handle is not reduced or eliminated, it can cause the rear brakes to drag as if the e-brake has been left on. Once the modifications are completed and adjusted, the driveshaft can be replaced.
Keeping Things In "Proportion"
Since we are changing the rear drums to discs we are going to have to do something about the brake system under the hood. Here's a couple options...
The new rear axle assembly...
The new rear axle assembly is aligned under the rearend of the car, again using the trans jack, and assembled to the rear suspension.
Once the brake lines were...
Once the brake lines were finished, John installed the new Fox-length rear axles, and buttoned up the rear bolting the rear cover back up.
Next the rear rotors, brake...
Next the rear rotors, brake pads, and calipers are installed.
New emergency brake cables...
New emergency brake cables from North Race Cars is the best way to go. They went in without a problem and to keep them in place you will need the e-brake C-clips (Ford PN 97413-S56).
To keep the e-brake cables...
To keep the e-brake cables from hanging down and hitting the tires, we bought a used set of stock SN-95 e-brake cable brackets that mount the lower control arms. You can also purchase these new from Ford PN F5ZZ-2530-AA.
Now the rearend fluids can...
Now the rearend fluids can be added. You will need two quarts of 75W-140 synthetic gear lubrication and 3.8 fluid ounces of friction modifier (Ford PN CM-19546-A1). To finish up the rearend, the rear sway bar, dampner, and driveshaft were bolted back up and the rear brake swap is completed. Make sure to modify your emergency brake assembly before installing your driveshaft back onto the car.
Option 1: A complete '94-'95 Mustang non-ABS brake master cylinder system, including a brake block, came with the SN-95 rear disc brake conversion from MPS Auto Salvage. This could be swapped in and some brake lines would need to be modified, but nothing too difficult.
Option 2: Richard from North Race Cars advises that this is the easiest solution and works great. First unscrew the black plug on the front of the brake block, then remove the plunger and spring. Lastly replace the plug with a combination valve plug PN FMS M-2450-A. This part can also be purchased at your local auto parts store.
To get the front brake system...
To get the front brake system swap started, we removed the front caliper bolts and calipers.
For now we just want to loosen...
For now we just want to loosen the strut bolts, but before doing so we supported the lower A-arm with a pole jack.
The cotter pin was removed...
The cotter pin was removed from the ball joint as well as the castle nut to the ball joint. At this time you will need to support the lower front control arm.
Now you will be able to remove...
Now you will be able to remove the front strut bolts and strut from spindle assembly.
Next, remove the wheel bearing...
Next, remove the wheel bearing dust cap, cotter pin, retainer, nut, and then the outer bearing. Now the front brake rotor can be removed.
Once the stock Fox-body dust...
Once the stock Fox-body dust shield and spindle assembly are removed we can start installing the SN-95 parts.
The SN-95 front spindle bolts...
The SN-95 front spindle bolts right into place as you tighten down the castle nut and replace the cotter pin. But what's the difference between '94-'95 spindles and '96-'04 spindles? All '94-'95 Mustang front spindles are a little different than the '96-'04 Mustang spindles, in that they pull the front wheels and tires inside the front fenders by about 3/8-inch more than the '96-'04 spindles. This offers a little more clearance for wider front wheels and tires especially on lowered cars where wheel lip clearance is a concern.
Now insert the end of the...
Now insert the end of the strut onto the SN-95 spindles and tighten down the two strut bolts.
Place the new SN-95 rotors...
Place the new SN-95 rotors onto the spindle assembly.
After the brake pads and caliper...
After the brake pads and caliper bracket are bolted onto the spindle assembly and rotor, the PBR front caliper can be installed. Note: There's a possibility that Ford changes the spindle and/or caliper tools after a couple years. We had to remove about 1-2 mm of material for caliper clearance around the spindle in a small area. The spindles we are using are '04 GT spindles, and it's possible the calipers may be late '90s calipers. With parts conversions like this, always remember nothing usually just bolts right up. Be prepared and do your homework.
Connect the brake lines from...
Connect the brake lines from the PBR front caliper to the hard lines. Note: The fittings were not compatible between the stock Fox-body hard line and the SN-95 brake hose. We used an Edelman fitting (PN EDE-258430 1/4 x 3/16-inch) to adapt the brake hose to the brake line. We found that this was necessary on the passenger side only. The SN-95 driver side brake hose/fitting is a direct fit onto the Fox-body brake line fitting. Repeat installation for the driver side brakes, then reattach the steering linkage, tighten the castle nut, and install the cotter pin to the spindle.