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How to Install Wilwood Rear Brake Kit on your 1999-2004 Mustang GT and V6

Installation Time

2 hours

American Muscle
Shop Parts in this Guide

Important Notice - Read this First

Before any tear-down or disassembly begins, review the following information:

• Review the wheel clearance diagram (figure 2, page 3) to verify that there is adequate clearance with the wheels you will be using with the installation.
• Rear brake kits are not supplied with hydraulic lines or fittings and may require the purchase of additional lines or fittings to complete the installation.  Wilwood offers an extensive listing of brake lines and fittings on our web site:
• Rear brake kits are not supplied with parking brake cables hardware or adapters.  Please see the note in the assembly instructions for vendor recommendations to purchase.
• Due to OEM production differences and other variations from vehicle to vehicle, the fastener hardware and other components in this kit may not be suitable for a specific application or vehicle.
• It is the responsibility of the purchaser and installer of this kit to verify suitability / fitment of all components and ensure all fasteners and hardware achieve complete and proper engagement.  Improper or inadequate engagement can lead to component failure.

Exploded Assembly Diagram

General Information and Disassembly Instructions

•Installation  of  this  kit  should  ONLY be  performed  by individuals  experienced  in  the  installation  and  proper operation of disc brake systems. Prior to any attempt to install this kit, please check the following to ensure a trouble free installation.
•Inspect the contents of this kit against the parts list to ensure that all components and hardware are included.
•Make sure this is the correct kit to fit the exact make and model year of your axle. This kit is designed for direct bolt-on installation to 1994 through 2004 model year Ford Mustang series hubs.
•Verify your wheel clearance using Figure 2.
•Verify that the factory axle and stud pattern matches the stud hole pattern in the hats supplied with this kit. Axles that have been modified with different size studs or lug patterns may require modifications to the hat that must be performed by a qualified machinist.


•Disassemble the original equipment rear brakes: Raise the rear wheels off the ground and support the rear suspension according to the vehicle manufacturer’s instructions.

•Remove the wheel.  Loosen the four bolts from the outboard side  of  the  upright  that  holds  the  stock  caliper  mounting bracket and lift off the bracket and stock caliper as one unit. You may have to unbolt the stock caliper from the caliper bracket before removal.  Then slide off the rotor.

•Clean, de-grease the stock hub while removing any nicks or

Assembly Instructions


• To ensure maximum performance from your parking brake system, the cables must be routed as straight as possible.  Bends in the cable can significantly reduce efficiency and thus reduce pull force at the brake. Tight bends must be avoided with a minimum recommended bend radius of 6" to 8".

• Cables should be properly restrained to prevent "straightening" of bends when tension is applied. Restrain movement of cable by affixing the cable sheath to body or chassis by fitting cable clamps at various points over the length of cable or by using original equipment cable attachments points. The clamping method chosen will require that cable sheath be held tightly without movement, crushing or causing interference to the internal cable.

• Cables must be initially pre-stretched by multiple applications of the brake handle, then re-adjusted to correct tension.

Assembly Instructions(numbers in parenthesis refer to the part list/diagram on the preceding page):

•The caliper mounting bracket (1) should be installed first with clean, dry threads on the mounting bolts. Install the bracket (1) on the outboard side of the stock bracket by sliding bolt (2) from the inboard side of the hub assembly through washer (3) and the sleeve (4) which is inserted inside the existing OEM caliper mounting holes.  Place two shim washers (16) between the hub and the caliper mounting bracket (1).  The mounting bracket (1) must tighten squarely against the outboard side of the stock bracket face.  Inspect for interference from casting irregularities, machining ridges, burrs, etc.  Use two shims (16) between the mounting bracket (1) and stock
bracket during initial trial fitting.

•With the larger I.D. side of the rotor (6) facing away from the hat (7), bolt rotor (6) to hat (7) through the backside of the rotor using washers (8), and bolts (9).  Be sure all bolts thread in smoothly and are snug. Then, torque all bolts in an alternating sequence to 103 in-lbs.  The rotor mounting bolts (9) must be lockwired using standard 0.032 inch diameter stainless steel safety wire as shown in Figure 3.  Please refer to Wilwood’s data sheet DS-386 (available at  for  complete  safety  wire  installation instructions.

•Install the hat and rotor assembly onto the hub.  Check to be sure the hat seats squarely against the hub. The hub must be free from any rust, debris, casting burrs, machining irregularities, etc.  Use several lug nuts to hold the rotor and hat firmly against the hub during the next phases of the installation and clearance checking procedures.

•Slide the brake pads (15) up into the caliper (10) from the bottom until the “v” spring clip snaps into place against the anvil.  They should install easily without interference.

•Lubricate caliper mounting studs and nuts with lightweight oil.  Install two shims (14) over each stud (13) on the radial mount bracket (2). Slide the caliper (10) in place over the studs and rotor and install the washer (12) and lock nut (11) to hold the caliper in place.  The caliper bleed screw should be pointing toward the rear of the vehicle. Snug the lock nuts (11) and check that the caliper (10) is centered over the rotor (6).  Add or subtract .016" shims (5) and/or .030 shims (16) as necessary between the caliper mounting bracket (1) and the stock bracket to center the caliper (10) on the rotor (6).

•Check that the outside radius of the brake pad (15) is aligned with the outside diameter radius of the rotor face.  Add or subtract shims (14) between the caliper (10) and caliper mounting bracket (1) to gain the proper alignment.

•Remove the lug nuts that were holding the hat/rotor in place.  Install the wheel and torque the lug nuts to manufacturer’s specification. Check to see that the wheel rotates freely without interference.

•Once all clearances have been checked, remove the wheel, caliper and rotor from the axle flange.  Secure the caliper mounting bracket (1) to the spindle face while applying red Loctite ® 271 on the bolt threads (2).  Torque the bolts (2) to 35 ft-lbs..  Reinstall the rotor and again use several lug nuts to hold it in place.  Reinstall the caliper, torque the caliper nuts (11) to 30 ft-lbs.

NOTE: OEM rubber brake hoses generally cannot be adapted to Wilwood calipers. The caliper inlet fitting is a M10 x 1.0 banjo. The preferred method is to use steel adapter fittings at the caliper, either straight, 45 or 90 degree and enough steel braided line to allow for full suspension travel and turning radius, lock to lock. Carefully route lines to prevent contact with moving suspension, brake or wheel components. Wilwood hose kits are designed for use in many different vehicle applications and it is the installer's responsibility to properly route and ensure adequate clearance and retention for brake hose components.

•Specified brake hose kits may not work with all Years, Makes and Models of vehicle that this brake kit is applicable to, due to possible OEM manufacturing changes during a production vehicle's life. It is the installer's responsibility to ensure that all fittings and hoses are the correct size and length, to ensure proper sealing and that they will not be subject to crimping, strain and abrasion from vibration or interference with suspension components, brake rotor or wheel.

•In absence of specific instructions for brake line routing, the installer must use his best professional judgment on correct routing and retention of lines to ensure safe operation. Test vehicle brake system per the 'minimum test' procedure stated within this document before driving. After road testing, inspect for leaks and interference. Initially after install and testing, perform frequent checks of the vehicle brake system and lines before driving, to confirm that there is no undue wear or interference not apparent from the initial test. Afterwards, perform periodic inspections for function, leaks and wear in a interval relative to the usage of vehicle.

•Repeat this entire procedure for the other wheel.

•Bleed the brake system.  Reference the general information and recommendations on page 5 for proper bleeding instructions. 

NOTE: The parking brake lock is cable actuated.  Connections are made with common cable ends that use 1/2” cable housing on the stop bracket, and a 1/8” to 9/64” cable with a crimped or welded ball end.  The caliper will accept the original equipment cable on some vehicles.  For other vehicles, new cable ends must be ordered to adapt the caliper to the vehicle’s original cable system.  For custom
installations, aftermarket hand brake kit suppliers can easily configure the cable with the correct attachment end.

•Install new parking brake cable (not included with kit).  Wilwood offers a generic style parking brake cable kit, P/N 330-9371 and adapters, 2 required (please call for specific application) for this kit which can be ordered separately from your local Wilwood dealer or by calling Wilwood customer service at (805) 388-1188. NOTE: Original equipment cable will not adapt to Wilwood calipers.

•Remove the lug nuts that were used to hold the hat/rotor assembly in place during caliper installation.  Install the wheel and torque the lug nuts to OEM specifications.

•Depress and hold brake pedal using moderate leg pressure.  While maintaining leg pressure on the pedal, completely engage and disengage parking brake lever until lever tension becomes consistent.  This will set the adjusting mechanism for the parking brake while tightening the lever feel.

•Bed in your brake pads per the procedure on the last page.

• After brake pads have been bedded, test the parking brake function on a slight slope.  Depress brake pedal, then apply parking brake. Release brake pedal.

Additional Information and Recommendations

NOTE: With the installation of after market disc brakes, the wheel track may change depending on the application. Check your wheel offset before final assembly.

•Please read the following concerning balancing the brake bias on 4 wheel disc vehicles.

This Ford Mustang kit can be operated using the stock OEM master cylinder.  However, as with most suspension and tire modifications (from OEM specifications), changing the brakes may alter the front to rear brake bias.  Rear brakes should not lock up before the front.  Brake system evaluation and tests should be performed by persons experienced in the installation and proper operation of brake systems.  Evaluation and tests should be performed under controlled conditions.  Start by making several stops from low speeds thengradually work up to higher speeds.  Always utilize safety restraint systems while operating vehicle.

•For optimum performance, fill and bleed the new system with Wilwood Hi-Temp° 570 grade fluid or EXP 600 Plus.  For severe braking or sustained high heat operation, use Wilwood EXP 600 Plus Racing Brake Fluid.  Used fluid must be completely flushed from the system to prevent contamination.  NOTE: Silicone DOT 5 brake fluid is NOT recommended for racing or performance driving.

•To properly bleed the brake system, begin with the caliper farthest from the master cylinder.  Bleed the outboard bleed screw first, then the inboard.  Repeat the procedure until all calipers in the system are bled, ending with the caliper closest to the master cylinder.  If the caliper is fitted with bleed screws on four corners, make sure the bottom bleed screws are tight.  Only bleed from the top bleed screws. NOTE: When using a new master cylinder, it is important to bench bleed the master cylinder first.

•Test the brake pedal.  It should be firm, not spongy, and stop at least 1 inch from the floor under heavy load.

If the brake pedal is spongy, bleed the system again.

If the brake pedal is initially firm, but then sinks to the floor, check the system for leaks.  Correct the leaks (if applicable) and then bleed the system again.

If the brake pedal goes to the floor and continued bleeding of the system does not correct the problem, either air may be trapped in the system, or a master cylinder with increased capacity (larger bore diameter) may be required.  Wilwood offers various
lightweight master cylinders with large fluid displacement capacities (custom fabricated mounting may be required.)

Brake Testing and Pad Bedding


• Make sure pedal is firm: Hold firm pressure on pedal for several minutes, it should remain in position without sinking.  If pedal sinks toward floor, check system for fluid leaks.  DO NOT drive vehicle if pedal does not stay firm or can be pushed to the floor with normal pressure.

•  At very low speed (2-5 mph) apply brakes hard several times while turning steering from full left to full right, repeat several times.  Remove the wheels and check that components are not touching, rubbing, or leaking.

• Carefully examine all brake components, brake lines, and fittings for leaks and interference.

• Make sure there is no interference with wheels or suspension components.

• Drive vehicle at low speed (15-20 mph) making moderate and hard stops.  Brakes should feel normal and positive.  Again check for leaks and interference.

•  Always test vehicle in a safe place where there is no danger to (or from) other people or vehicles.

•  Always wear seat belts and make use of all safety equipment.


•Pump brakes at low speed to assure proper operation.  On the race track, or other safe location, make a series of hard stops until some brake fade is experienced.  Allow brakes to cool while driving at moderate speed to avoid use of the brakes.  This process will properly burnish the brake pads, offering maximum performance.

This guide applies to Vehicle years: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 and Submodels: GT, V6