Subaru WRX Brake, Steering, and Suspension Installation

Which Part Fits Which Car

Treat every fastener and every damper as year-specific until the part number matches that chassis. A Baja or Legacy rotor job follows the same sequence as a WRX rotor job, and the bolt sizes and torque values still change with the car. The table is the split that decides whether the part in the box belongs on the car.

20365FG500 is the 2010 STI rear shock, listed at 4.10 lb. The 2013 WRX rear shock is 20365FG530, listed at 10.30 lb, and that number is replaced by 20365FG531. A 2013 STI uses 20365FG510. Three part numbers, three dampers, even though all three cars sit on the 2008–2014 chassis.

A 2015 Impreza base and a 2015 WRX do not share front struts. The Impreza sedan base right and left completes are 20310FJ300 and 20310FJ310. The 2015 WRX 2.0 right and left completes are 20310VA040 and 20310VA050. A WRX coilover for that year is not a bolt-on for the Impreza, and an earlier WRX coilover is a different chassis again.

Hub bolt circle decides a big-brake swap. A 2004 STI is 5x100, with a 56.1 mm centerbore, the same pattern as a 2002–2014 WRX. A 2005–2007 STI is 5x114.3, so those rotors need the 5x114.3 hub and knuckle. From 2015 the WRX itself moves to 5x114.3, and a 2002–2014 WRX rotor stays on the 5x100 hub.

Struts, Springs, and Inserts

Three jobs get lumped together and they are not the same. A spring swap reuses the stock damper. A coilover replaces the strut. A Koni insert reuses the stock strut body and the stock spring, which means the housing has to be opened and the insert installed in that body. Cold, salted roads with deep potholes are a poor match for a coilover. On a 2011 WRX in that climate, a damper and spring is the combination that still absorbs a hit. An insert is that kind of job. A coilover is the other one.

A 2008-and-later Impreza rear suspension is a different geometry from anything older. It does not go into a 1998 or any other pre-2008 car. A 2002–2007 suspension can be adapted into an older GC, and the rear strut-mount bolt circle still has to be adapted. The fronts are not a free interchange either once the top-hat bolt pattern changes.

Taking the strut out

On a 2005–2007 WRX the front strut comes out in this order. The brake-hose bolt and the ABS-harness bolt come off the strut first, so the line is not the thing holding the housing. Scribe the camber-adjusting bolt to the strut before either pinch bolt is loose. Hold the head of that adjusting bolt while the self-locking nut comes off, or the eccentric walks and the mark is useless. Then remove the two bolts that clamp the housing to the strut. The three nuts that hold the mount to the body come off last. Leave those top nuts threaded until the knuckle is free. If they come off first, the spring is the only thing left in the tower.

The rear is the same idea with a different lower joint. Remove the bolts that hold the strut to the lower arm, then the top nuts, then pull the strut. Reinstall in reverse. Plan on setting the car down, measuring, and picking it back up. One car took four ride-height passes and two alignments. Too high and the car stands like a wagon. Too low and the fender liners get eaten and the fenders get pushed out.

Putting the spring back

Compress the coil with a spring compressor before the rod nut comes off. The strut-mount socket for that nut is special tool 927760000. The spring end has to sit in the seat, and the upper seat has a clock position. A helper and the dust cover go on the rod before the rubber seat and the upper seat. Pull the rod all the way up, set the mount, and snug a new self-locking nut. Hold the rod with a hex so it does not spin, then torque that nut to 55 N·m (41 ft-lb). Release the compressor slowly.

Air in the damper kills the damping even when the hardware is right. Stand the strut rod-up, move the rod to mid-stroke, and try to stroke it with your fingertips. If it travels 10 mm (0.39 in) or more, purge it: rod up and fully extended, flip it rod-down and vertical, fully compress, and repeat three or four times. Finish rod-up. If it gets laid on its side afterward, check for air again. Rod play past 0.8 mm (0.031 in), measured with a 20 N load at 10 mm from full extension, means the strut is done.

Line the camber-bolt mark up with the mark on the lower side of the strut, use a new self-locking nut, and hold the bolt head while the nut is tightened. Then align the car. A strut that leaked, or a rod that binds, gets replaced before it goes back in.

Camber Bolts and the Top Mount

Generic McPherson instructions tell you to replace the upper strut-to-knuckle bolt with a camber bolt. That is the first eccentric on a car that left the factory with two plain bolts. On these cars the factory already put the eccentric in the upper hole. The second, aftermarket bolt goes in the lower hole. Replacing the upper bolt with the kit bolt fights the bolt that is already doing that job. On one coilover install the kit bolt would not sit in the upper hole at all. Mark the factory bolt’s clocking before it comes out, and put it back on that mark.

A front-spring clunk after STI pink springs on a 2008 Impreza was the top mount, not a bad spring. The domed washer goes small side up, and it sits on top of the upper perch. Under the perch, or flipped, it clunks. The upper perch has three holes. The center hole is centered on the strut and faces straight out. Check the sway-bar links before you pull the strut again. A loose link is the usual front knock, and it sounds like a spring.

Arms, Bushings, and Sway Bars

A lateral link and a trailing link are different arms. The bushings are different, and a writeup for one does not install the other. The rear of the trailing link is its own bushing again. Read the arm name on the part before the press comes out.

The 2012 WRX front lower arm, right side, is 20202SC003. The 2012 STI arm on that corner is the aluminum 20202FG041. The 2015 WRX and STI right arm is 20202VA001. Those are three arms. On one 2012 WRX, a 2015–2019 STI arm lined up at the knuckle and the rearward bushing would not pass the WRX chassis stud. That bushing’s outer diameter was 2.37 in, and the metal insert needed a 3/4 in inner diameter to fit the stud that was already in the WRX. The stud is not a bolt you swap for an STI stud as part of a normal arm install. Use the arm for the chassis, or use a bushing whose insert matches the stud that is in the car.

Lower-arm bushings on a 2011 Forester sit at an angle that a rented press kit often cannot cup. Sockets from the kit bottom out in the wrong place. One side came out with heat and a saw in about 45 minutes. The second side, once the cut was understood, took about five. A 1/4 in bit, used to perforate the rubber before the heat, is the other way through a large rubber bushing that has little metal to press against. Replacing the whole arm avoids a thread that gets wrecked while the sleeve is being driven. That is the safer path when the press will not square up.

On a front control-arm outer metal sleeve, two partial-depth cuts about 1/4 in apart let the sleeve shear and collapse. A cut that goes through the arm scraps the arm. Pound only after the cuts are short of the bore.

An anti-lift kit replaces the stock inner bushing. The short version is remove that bushing and install the kit. Writeups that skip the orientation of the new piece are how the geometry ends up wrong, so the kit’s own clocking is part of the install, not a trim step.

Sway bars split by year at the mounts. A 2002–2003 WRX rear bar mount is its own upgrade. From 2004 the brackets, including aftermarket brackets of that shape, are a different mount. Endlinks are a separate rattle from the bar. A 1994 Impreza L two-wheel-drive has no rear bar mounts. An all-wheel-drive bar kit does not bolt on. One rally build’s plan was welded brackets and wagon rear lateral links. That is fabrication, not a kit.

A ball joint is its own job from the strut. On the 2005–2007 procedure the joint-to-housing bolt is 50 N·m (37 ft-lb), and the taper gets no grease. The castle nut is 40 N·m (30 ft-lb), or 30 N·m (22 ft-lb) on an STI, then tightened further within 60° until the cotter goes through. Replace the joint when play under a 686 N (154 lb) load exceeds 0.3 mm (0.012 in). A torn dust cover means a new joint, not a new boot on a worn stud.

A CV joint with a positive retention feature is not a boot job. Those joints are built so they do not come apart, and a boot kit will not make them serviceable. Replace the axle. A boot kit is for a joint that is built to be taken apart. Clicking in a tight turn under 10 mph, after a torn boot has been open for a while, is a bad joint, not a clamp.

Brakes, Lines, and the Parking Brake

Pad shape follows the caliper, not the bumper. The 2006–2007 WRX front pad kit is 26296FE070. The 2006 STI front pad kit is 26296FE100. Pads sold for a 2005-and-earlier sliding caliper do not fit the four-piston WRX caliper. On the 2006 Impreza rotor chart the WRX front rotor is 293 mm, part 26300AE02C, and the 2.5i front rotor is 277 mm, part 26300AE00C. A counter that hands you the earlier pads often hands you the smaller rotor with them. The pin spring that retains the pad pins on a four-piston caliper bends if it is pried. A sliding-caliper rebuild and a Brembo rebuild are the same kind of seal job. They are not the same piston count, and the hardware does not mix.

A rotor that has rusted to the hub has two threaded holes in the hat. On the 2005–2007 rear disc, those take 8 mm bolts, and the bolts push the rotor off the hub. Do that only after the parking-brake shoes are backed off. Driving the bolts into a hat that is still clamped by the shoes loads the hat, not the rust.

The rear rotor on these cars is a disc with a drum in the hat. The parking-brake shoes live inside that drum. They do not unwind or fall off when the rotor comes off, as long as the cable is released and the shoes are backed away from the drum. Release the lever, unbolt the caliper, and hang it so the hose is not the support. If the hat will not come off, pull the rubber plug in the backing plate and turn the star adjuster with a flat screwdriver until the shoes clear. Then the 8 mm bolts, if the hat is seized to the hub. The shoes come off only after that, hold-down pins first, then the cable end at the shoe lever.

There are two adjustments, and both get used. One is the star wheel at the shoes. The other is at the lever. That procedure lists 7 to 8 notches with 196 N (44 lb) at the lever. Grease stays on the shoe contact points at the backing plate, the anchor, the strut, and the adjuster. It stays off the lining. A 2002 WRX rear rotor is this same drum-in-hat layout. The shoe diameters above are the 2005–2007 split, STI versus the other cars in that procedure.

Stainless lines are a bleed job, not a hose job. Keep the master cylinder full. Air pulled in through the master ends up in the ABS unit, and a pedal bleed leaves it there. The performance-hose procedure that cycles the ABS pump applies to cars that have that diagnostic plug. A 2006 STI does not have that plug, so the bleed on that car stays a pedal bleed with the reservoir kept full. Watch the reservoir the whole time, at every bleeder.

Steering Rack and the Angle Sensor

Rack bushings are not a rack replacement, and the two cars next to each other in 2005 do not share a gear. The 2005 WRX steering gear is 34110FE580, which replaces 34110FE590, listed at 33.30 lb. The 2005–2007 STI gear is 34110FE600, listed at 26.30 lb. Swapping a newer gear into an older crossmember is a different mount, not a bushing job. Match the gear to the year before the crossmember bolts come out.

On a 2006–2007 STI, rack-bushing work has thrown a steering-angle-sensor fault on at least three cars. One of those still faulted after the battery was disconnected and the column and the rack were marked. A bad sensor takes down both the driver-controlled center differential and the stability control. Tape the column shaft to the rack housing, and mark both, before a bushing bolt is loose. Do not let the shaft rotate relative to the rack while the bushings are out. The same fault shows up from other work around the column, so the rule is the shaft position, not only the bushing.

A noisy, leaking pump on a 2003 WRX is a pump and line job. It is not fixed by the rack-bushing procedure, and a later pump is not a guaranteed bolt-in for that bracket and those hoses. Fix the leak that is actually wet before the pump is condemned.

Install Order

Do the mechanical work before the alignment, and do the alignment after the car has been set down and the height is done. Bushings and bars can go in with the struts. Brake hydraulics finish with a bleed and a pedal check before the car rolls.

1. Confirm the part numbers. Strut, arm, pad, rotor bolt circle, and steering gear. A wrong damper bolts on and still rides wrong.
2. Support the car on stands. Wheels off. Crack the top-mount nuts and leave them threaded.
3. Free the lines. Brake-hose bracket and ABS clip off the strut. Hang a caliper. Do not hang the car on a hose.
4. Mark the camber bolt. Then the lower bolts, holding the eccentric head. Then the top nuts. Rear strut lower bolts, then the top nuts.
5. Assemble the spring on the damper. Seat the coil, purge air, torque the rod nut, washer small-side-up on top of the perch, center perch hole facing out.
6. Arms and bars. A lateral link and a trailing link are different parts. Install the arms, then the sway-bar brackets and endlinks.
7. Brakes. Shoes backed off before a drum-in-hat rotor. Pads for that caliper. Lines tight, master kept full, bleed from the far corner in.
8. Steering. Column taped to the rack before bushings. Gear part number matched to the year if the rack itself is coming out.
9. Set the height on a level floor. More than one pass is normal. Then align, and recheck the camber-bolt marks after the alignment torque.

FAQ

Will 2005 STI Brembos fit a 5x100 Impreza?

The 2004 STI rotors are 5x100, the same bolt circle as a 2002–2014 WRX. The 2005–2007 STI rotors are 5x114.3 and need that hub and knuckle. An adapter does not change the stud pattern.

Does rear shock 20365FG500 fit a 2013 WRX?

20365FG500 is the 2010 STI rear shock. The 2013 WRX rear shock is 20365FG530, replaced by 20365FG531. The 2013 STI shock is 20365FG510.

Where does an aftermarket camber bolt go?

In the lower strut-to-knuckle hole. The upper hole already has the factory eccentric. Generic instructions that replace the upper bolt are for cars that did not come with one.

Will the parking brake unwind when the rear rotor comes off?

The shoes stay on the backing plate. Release the lever and back the star adjuster off until they clear the drum in the hat. Use the 8 mm holes after the shoes are clear.

Do 2015 WRX coilovers fit a 2015 Impreza?

The Impreza base front struts are 20310FJ300 and 20310FJ310. The 2015 WRX 2.0 front struts are 20310VA040 and 20310VA050. A coilover built for one of those struts stays on that chassis.

What fails if the steering shaft rotates during rack bushings?

On a 2006–2007 STI the steering-angle sensor faults, and that fault takes out the center differential control and the stability control. Tape and mark the shaft to the rack before the bushings move.