Steve Baur
Former Editor, Modified Mustangs & Fords
May 1, 2003
Photos By: Rick Jensen

The Problem

Slipping and sliding is now a thing of the past. And we look good, too, thanks to Ford Racing Performance Parts and Discount Tire.

Let's face it, Fox-body 5L Mustangs have never been known for their stopping prowess. Ten and a half inch rotors up front and 9-inch drums out back just don't cut it in today's world of anti-lock, four-wheel disc braking. And if you have brought your pony to ultra-modern power levels, like we have, you're not only under the gun, you're under the firing squad!

Since supercharging our '90 GT with ProCharger's P-1SC huffer, our horse gained 130-plus rear-wheel horsepower and is hauling its tail like never before. Stopping the pony was a problem prior to the power enhancement, and so we looked to Ford Racing to provide a remedy.

The Solution

In the heart of the Ford Racing Performance Parts (FRPP) catalog, one will find the five-Lug Front/Rear Super Heavy-Duty Cobra Disc Brake Conversion Kit, otherwise known as PNM-2300-K. We went to FRPP for improved braking mainly because it uses all factory equipment. If we need to do a brake job, all we have to do is pay a visit to our local parts store for replacement rotors or pads. We also took into consideration the extensive testing these parts are subjected to before they go on a production vehicle.

The kit is quite inclusive, providing everything you need to convert your failing Fox braking system into a stalwart stopper. Starting at the rear is a new set of 11.65-inch rotors and calipers, new axle shafts, brake lines and hoses. Four parking brake cables are supplied, as two are for '87-92 Mustangs, and the other two are for '93 models. Moving forward, giant 13-inch rotors and Cobra-embossed calipers really toss the anchor out when you step on the negative-G pedal, and new spindles with sealed-bearing hubs make changing rotors a snap. More brake hoses and lines are provided for the front brakes, and dust shields are supplied for all four corners. FRPP also includes a new master cylinder, brake booster, and an adjustable proportioning valve to ensure the four-wheel discs perform at their peak.

We did mention the M-2300-K kit is a five-lug system. This requires a new set of wheels if you haven't already added the additional lug studs. Having the 13-inch rotors up front will also affect your wheel choice; with whatever wheel you choose needing the appropriate backspacing and clearance for the calipers. FRPP recommends a 17x8-inch wheel with a five-hole, 4.5-inch diameter mounting pattern, and 5.75-inch backspacing. This makes things very easy, as many of the factory Ford wheels already have this. Flipping through the FRPP catalog, we counted six different wheel styles that would work, and adding the '94-98 17x8-inch GT wheels would increase the number by two. So you have quite a few wheel choices without even going to the aftermarket, which has an immense number of custom wheels available with that backspacing.

We had originally planned to go with some silver Bullitt-style wheels, but after talking with Dan Meadows at Discount Tire Direct, we opted for a set of Fittipaldi Force rims in a 17x8-inch size. The Fittipaldis are sold exclusively through Discount Tire and are available in 17x8-18x8.5-inch sizes. The Force rims featured a 35mm (5.85 inches) backspacing. Any more and we run the risk of contact with the front lower control arms. The wheels are machine cast and clearcoated for easy cleaning and a shiny finish, and once we checked them out on a Thunderbird in Discount Tire's gallery on its Web site, we knew they would give our pony a unique style and add a little pizzazz to the stock body.

The wheel and tire package came in at $1,525, and Discount also supplied us with Gorilla chrome-plated lug nuts that use a special socket to install them. The design of the wheel necessitates the use of a slim lug, and you certainly don't want to use some horrid open lug on your hot new rims.

The new brake hoses are attached to brackets that are to be bolted to the shock support. To save time, we tack welded them to the support until we replace the shocks. Then we shall drill and bolt them to the bracket. The FRPP kit also includes two new steel brake lines. These are perfectly contoured to the axle.

For rubber, Discount Tire recommended Nitto's NT555 radial tires. We opted for the '94-98 GT factory size of 245/45x17, but in hindsight, we may have been better off with a 235/45. The 245 increased the overall diameter of the wheel and tire, which not only changed our gear ratio, but also put the rubber closer to the fender lips than we would prefer.

FRPP does say the kit may require the rear inner fender lips to be rolled, and bottoming out several times on the way home confirmed this (not that our pothole-infested New Jersey highways helped any). We also think the factory 139,000-mile rear shocks might be a little on the soft and worn out side complicating the matter. Going with the 235-size tire might lessen this problem a little, but if you plan to lower the car or have already done so, rolling the fenders will be a necessity.

Installation

While the majority of the Cobra brake kit can be installed by the average enthusiast, there are a few modifications that require some special tools, which you may not have. Installation is pretty straightforward with the only real difficult parts being the installation of the new brake booster, cutting and flaring one brake line, welding the parking brake handle, and adjusting the proportioning valve.

Testing and adjusting the proportioning valve may run into another day, but it is time well spent, as you don't want to have the brakes working incorrectly. Adjustment required a bit of wheel lock up to verify the back brakes lock after the front ones do. This should be done on a closed course of some sort, preferably on a low-traction surface like wet pavement. That will keep you from flat spotting the tires. The instructions with the valve give you a baseline to start with and it is fairly close. We made one full turn clockwise to increase the rear bias and after making a run, backed it off half a turn to find the sweet spot.

The kit comes with some instructions. They are rather brief and the picture quality wasn't the best. However, Ford Racing told us the instructions for the kit are being completely revamped as this was being written, and all kits shall be equipped with them by the time you read this. They also recommend you have a '94-up Mustang service manual handy.

If you're not familiar with braking systems, you might want to get a professional to install the system. This will ensure the components are installed properly and the system works like it should. Once the kit is installed though, performing brake maintenance is a snap. Two bolts hold each caliper on, and the rotors are held in place by the calipers. No messy bearing to repack and no springs and other assorted parts to come flying off of the brake drum.

Work on our '90 Mustang GT was performed by Eric Ledbetter of Eric's Performance in Old Bridge, New Jersey. Eric has been working on cars, and Mustangs in particular, for years. He also owns a 9-second '67 Mustang, and an 11-second late-model notchback, so it's safe to say he knows his way around a Blue Oval. With a knowledgeable technician turning the wrenches, the complete kit can be installed in about 8-10 hours. The bulk of the installation can be found in the captions within the story.

Evaluation

The new spindle is installed with this spacer. Then replace the tie rod end and strut bolts.

To verify the Ford components were worth the expense, we performed before and after brake testing at Old Bridge Township Raceway Park, New Jersey. Although closed for the winter (it was mid January when this was written), the track lets us use the open space to perform such tests. After complaining about the brakes in the opening paragraph, one should expect a monumental improvement in deceleration and we weren't disappointed.

During our baseline runs, we managed to lock up the warped stock rotors a few times, as evident from the pictures. Once we found the right pedal modulation, we still went sailing past any acceptable distance. Using our Stalker ATS radar equipment to verify our braking data, we averaged 485 feet slowing from 100-0. With the Cobra four-wheel discs stopping us, that average was cut by 61 feet to 424. Just to give you an idea, 60 feet is about the length of four Mustangs. Further investigation of the chart will show you we gained stopping power in 70-0 and 60-0 tests, also. Add to that the ease of working on the disc brakes, and the kit's $1,795 price tag just bought you a whole lot of peace of mind.

We have to add the new tires and wheels certainly had an affect on braking, also. The 245-size tires offer a bigger footprint than the 225-size rubber we had on the factory pony wheels. While both sets of tires were made by Nitto, the 225s were an all-season tread and not geared toward the same performance level of the NT555s.

We couldn't be more pleased with the Ford Racing Cobra Disc Brake Conversion. The performance gain was absolutely fantastic and something that every Fox Mustang should be blessed with, even if it is still stock as a rock under the hood. The kit also gave us the opportunity to bolt on some awesome looking wheels from Discount Tire, giving it a well-deserved aesthetic upgrade. Fox Mustang owners, if you need improved braking, Ford Racing can give it to you.

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