Fitting Lowering Springs to 964

Nov 13 2008

Tools Required
The tools listed below are just the specific ones we can recall using.
-Coil spring compressor (rent)
-5 mm Allen head wrench
-10mm Allen head which fits on a breaker bar (mine are 3/8″ drive, I used a 3/8 to ½” adapter)
-Torque wrench (150 ft-lb.)
-17 mm open end wrench
-11 mm flare wrench
-22 mm socket
-Air impact wrench & sockets.

Front Strut Removal
1. Remove front wheel.
2. Spray your favourite penetrating lubricant on the threads of the two bolts which connect the strut to the wheel carrier.
3. Disconnect brake pad wear sensor and the wheel rotation sensor. This is accomplished by opening the clamshell holder with a small screwdriver and unplugging the connectors.
4. Remove the brake pad sensor/wheel rotation sensor common cable from its holder on the strut by pulling it out.
5. Remove the wheel rotation sensor grounding wire and reinstall the screw to keep dirt out.
6. Using an 11 mm flare wrench loosen the brake line at the strut.
7. Remove the clip which secures the brake line to the strut by driving it up with a punch.
8. Using a pair of wrenches (17 and 11 mm) finish separating the brake lines and remove them from the bracket on the strut. Quickly reconnect them outside of the bracket.
9. Using a 10 mm Allen head and a breaker bar loosen the two bolts which connect the strut to the wheel carrier. Remove the upper bolt but not the lower one just yet. When these bolts are removed the wheel carrier will be free to rotate down so find some method to support it.
10. Remove the four nuts and washers which secure the top of the strut to the body.
11. Carefully remove the remaining bolt from the strut/wheel carrier and remove the strut from the car.

Rear Strut Removal
1. Remove the air cleaner assembly and blower assembly.
2. Remove the rear wheel.
3. Using air tools and/or a large breaker bar remove the lower strut mounting bolt.
4. Remove the three nuts and washers which secure the top of the strut to the body.
5. Remove the strut from the car.

Spring Replacement
The spring replacement process is similar for both the front and rear. Basically you use a spring compressor to release the spring force on the top spring mount and then remove the top retaining bolt. An air impact wrench greatly simplifies this process. On the front springs of my car the preload of the springs was sufficiently low that I did not need to use a spring compressor. This is definitely NOT the case with the rears. The rears have approximately three inches of preload. If you were to remove the top nut without using a spring compressor the top plate would probably be launched through the ceiling!

The installation notes which came with my H&R springs said to cut about ¾” off the bump stop. It is important to cut this off the top of the bump stop as the bottom has a feature which retains the bellows which shields the strut from water and grit.
When reinstalling the top spring mounts be sure to get the correct orientation of the lower and upper mounting bolts with respect to each other.

Front Strut Installation
Replacement is essentially the reverse of the removal process. One of the tricky parts of installing the front strut is to get the upper strut mounting bolt in after you get the lower one in place. The trick I used is to thread a lug nut on one of the wheels studs and use a socket on a speed wrench as a lever to lever the wheel carrier assembly into place. The factory manual says the lower bolts, nuts and washers after every removal. Be sure to use anti-seize compound on the treads and between the bolt head and its washer.

Rear Strut Installation
Replacement is essentially the reverse of removal process. The factory manual says to lubricate the upper strut mount with tire assembly compound on 1991 and later cars. See the note under the bolt torques section below. I assume this is because of the tight fit into the shock tower. I used a little soapy water. Be sure to use anti-seize compound on the bolt threads.

Finishing the Job
Reinstall the blower and air cleaner assembly. Be sure to use a thread locker on the four nuts which bolt the air box to the air flow sensor. You don’t want your engine to ingest those! Since the front brake lines were disconnected you will need to bleed the front brakes. I made no attempt to set the ride height of the car since the car must be corner balanced and aligned.

Bolt Torques
Front strut upper mounting bolts (4) 27 ft-lbs
Front strut lower mounting bolts (2) 100 ft-lbs
Rear strut upper mounting bolts (3) 89-90, 15 ft-lbs, 91 on, 27 ft-lbs.*
Rear strut lower mounting bolt (1) 147 ft-lbs
* The factory manual says that the rear struts were redesigned in 1991. The later model design has the strut protruding about 1″ from the strut mount and has relatively thick (3.1 mm) washers under the nuts.

Categories Categories: Tips Porsche 964 1990-94

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