Tilton Subaru WRX-STI Package User Manual
INSTALLATION INSTRUCTIONS
Subaru WRX/STI Clutch Package
Description
Tilton’s Subaru WRX/STI clutch packages are designed to oer increased torque and reduced
rotating mass. In addition, these clutch packages include a concentric hydraulic release
bearing assembly that eliminates the stock external slave cylinder and related linkage. The
clutch provides high torque capacity that enables you to “up the boost,” while it’s reduced
rotating mass results in increased horsepower to the wheels. The hydraulic release bearing
self-adjusts for clutch wear and provides great pedal feel.
Note: This instruction sheet is designed to supplement the general instruc-
tions sheets supplied with the individual components of the clutch package.
installation
Flywheel
1. Install ywheel onto engine. Torque OEM ywheel-to-crankshaft bolts to factory
specication.
clutch Discs
2. Install clutch discs into the clutch. For Carbon/Carbon clutches, orient the clutch hub as
shown in Diagram 1. For Cerametallic clutches, align hubs as shown in Diagram 2.
Be sure to align discs with an alignment tool or spare input shaft.
clutch
3. Mount clutch onto the ywheel with the supplied aircraft grade hardware. Torque
hardware to 18 lb -ft using oil or thread locking compound. The tips of the spring ngers
should taper slightly towards the transmission. The spring must not be inverted.
4. Test t the transmission to the engine to conrm that there is no interference between
the clutch’s spring retaining hardware and the inside of the transmission case. There
should be .075” of clearance, but due to variations in transmission castings the clearance
may be decreased. If there is interference, you may have to grind the tips of the spring
retaining screws to be ush with the nuts and/or grind some material from the transmis-
sion case.
98 -1124
Diagram 1
Oset
FLYWHEEL
CLUTCH COVER
Diagram 2
FLYWHEEL
hyDraulic release Bearing assemBly
1. Remove the existing Original Equipment (OE) slave cylinder, fork arm and release bearing
from the transmission.
2. Tighten the two AN3 male-to -male hydraulic ttings into the two ports of the hydraulic
release bearing assembly. Do not use any thread sealing compound, as the tting seal on
the taper and not the threads.
3. Thoroughly clean o the pilot tube (the tube around the input shaft on which the origi-
nal release bearing would slide)
removing all dirt and grease.
4. Test t the hydraulic release bearing (HRB) assembly onto the transmission’s pilot tube
to ensure it is sitting at and parallel. Due to variations in transmission castings, the HRB
may not sit at. You can check if it is sitting at by placing a bubble level across the top of
the release bearing.
Note: Flatness can be corrected by:
5-speed transmissions: Grinding/sanding the casting imperfections on the pilot tube.
6-speed transmissions: Grinding the heads of the four bolts at.
5. Place a small bead of high temperature RTV silicone around the pilot tube ½” – 1” from
its base. This will help to hold the hydraulic release bearing assembly in place once it is
installed.
V V
CLUTCH COVER
V = Solid, 8 rivet, outer (.375" thick)
6. The base of the hydraulic release bearing assembly has a at side. This is for
clearance reasons. Rotate the assembly until the at side is approximately parallel
with the ground. The relief cut on the underside of the base is there for clearance
of a rib in the transmission case. Slide the assembly all of the way onto the pilot
tube making sure that the at side and the relief cut on the bottom clear their
respective transmission protrusions.
7. Once installed in the transmission, the two ports of the hydraulic release bearing
should be located 15˚ o vertical. The port on the left side (looking into the trans-
mission from the engine end) is the port used for the bleed line. The port on the
right is for the line that routes to the master cylinder.
hyDraulic lines
1. Determine the length of hydraulic line you will need to run to the master cylinder
and the length you will require for a bleed line.
2. Utilizing the 90” long piece of AN3 steel braided line provided with the kit, cut the
line to the needed lengths.
3. Complete the lines using the supplied ttings. See Figure 2 for details on installing
the ttings onto the lines.
4. Connect the bleed line to the port on the left side of the hydraulic release bearing
assembly. Route the bleed line outside of the transmission/bellhousing for easy
access.
5. Connect the supply line to the port on the right side of the hydraulic release bear-
ing assembly and connect to the master cylinder.
6. Route both lines clear of heat sources such as the exhaust system and/or turbo.
Also, make sure that the lines will stay clear of the clutch and ywheel.
master cylinDer selection
The master cylinder bore diameter size has a large inuence on the operation of the
clutch. Its selection is often a matter of personal preference. If the bore size is too
small it will require an excessive amount of pedal travel or may not disengage the
clutch at all. If the bore size is too large it will be too hard to push the clutch pedal and
pedal stroke will be short.
In general, a ¾” bore master cylinder is recommended for use with Tilton 7.25”
clutches. The stock WRX/STI master cylinder has an 11/16” bore diameter. This master
cylinder is suitable for use with the Tilton 7.25” carbon clutch, since the carbon plates
do not warp. A ¾” bore master cylinder is recommended for use with the cerametallic
and hybrid clutches, as more uid volume displacement is required to compensate for
clutch plate warpage from use.
Titan Motorsports (407.277.8423) oers ¾” bore master cylinder kit for the WRX/STi.
Diagram 3
NOTE: Mitsubishi EVO VIII spring shown for example only.
“helper” spring removal
Remove the “helper/over-center” spring from the clutch
pedal assembly as shown in Figure 3. This spring is designed
to help overcome the resistance of the stock clutch’s
diaphragm spring, making clutch disengagement easier
(less eort). This spring is not needed for use with the
Tilton clutch package, due to the supplied hydraulic release
bearing assembly.
Diagram 4
clutch peDal stop
A positive clutch pedal stop must be used to prevent over-stroking the hydraulic
release bearing piston and the clutch. For access reasons, in many cars it is not easy to
determine how far the master cylinder is being stroked.
The method listed below provides a very eective method for adjusting the pedal
stop:
1. Lift the drive wheels o the ground and support the car on jack stands.
2. With the engine o, place the gearbox in rst gear and have someone attempt to
rotate the drive wheels.
3. Depress the clutch pedal slowly until the clutch disengages and the drive wheels
can be rotated.
4. Adjust pedal stop to allow another 1/4” of pedal travel. This should provide
clean release of the clutch. Do not stroke the pedal any further than this point
throughout this procedure, otherwise you will over-stroke the clutch.
Tilton Engineering, Inc. 25 Easy Street • PO Box 1787 • Buellton, CA 93427 • www.tiltonracing.com
Adjustable
Pedal stop
FIREWALL
Pedal position where
pedal stop should be set.
Never travel clutch
pedal past t his point!
Pedal position where
clutch breaks free.
1/4" additional travel
(exaggerated for clarity)
Loading...