Celle

I followed our guru Peter Zimmermann's advice and upgraded my Euro stock 1989 Carrera with four new Bilstein HD shocks. The car had four original Boge's and has 137.000 kilometres (85.000 miles). It's used for spirited street driving only - no track. I was looking for a good rigid suspension, without losing too much ride comfort (some European roads are crappy).

The car felt completely different when I took it for a spin an hour ago - much more stable and steadfast. I don't have the impression that it has a harder ride now, it just feels more "rigid".

The whole procedure took me about 5 hours - 3.5 for fronts and 1.5 for rears. I did it all alone, except for a few harder tasks where I was given a hand by a friend who is also a mechanic.

I used Wayne's "101 Projects" book as a guideline, augmented by the tons of advice and good tricks that I picked up by doing an extensive search of this forum and the one of Pelican Parts. I found the procedure in the Bentley manual too elaborate and including unnecessary actions.

I made up a "checklist for the DIY-dummie" like myself, stuck it on the windshield with some tape, and fired ahead. I just finetuned the checklist with my experiences while actually doing the job today, and here it is for the benefit of all of you who want to do the same upgrade:

1. Have paper towels, rags and all tools within reach.
2. Jack up front of car, put on jack stands.
3. Remove wheels.
4. Put newspapers or cardboard under wheel wells.
5. Put protective tape on fender lips to avoid scratches.
6. Remove upper strut nut in trunk (22 mm). I used an impact wrench for this.
 Hold large washer with large channel locks to avoid it from turning. Use rag to avoid marring it.
7. Remove brake cable from C-clips on strut and fender well.
8. Pull down strut by grabbing it by the upper dust shield and remove dust shield (upper part of strut), large plastic washer and rubber bump stop from strut by pulling it down low enough so you can take these off in the wheel well.
9. Put strut back in upper mount to give stability to remove gland nut. Finger tighten nut in trunk.
10. Remove gland (collar) nut of old piston with large channel locks or pipe wrench.
 Counterclockwise turn!
 Avoid strut to turn while removing gland nut. I held it with a large vise grip.
 Difficult to perform alone – better have someone to give you a (strong) hand.
11. Now take off the nut in the trunk again and gently pull down shock piston until you can tilt the strut out of the wheel well.
 Watch brake line, do not overstretch it! I could just tilt the old shock out of the wheel well without overstretching the brake line.
12. Gently take out the old piston from the strut. Watch out, there is a lot of hydraulic fluid coming out of the strut when pulling out the piston.
13. Clean out all oil from the strut housing. You will need several rags. There should be no oil left in the strut housing.
14. Remove rust or dirt from threaded portion of strut housing.
15. Loosen up new insert by pushing in/letting out a few times.
16. Gently install new insert in housing. Compress piston low enough to be able to tilt the strut back into the wheel well and place it directly into the upper mount hole. Considerable force is needed. Difficult to perform alone. Here the protective tape on the fender earns its pay…
 May need jack to lift A-Arm to assist shock rod high enough into mount.
17. Put the gland nut on and really tighten gland nut with pipe wrench or large channel locks while someone holds the strut to keep it from turning.
18. Pull strut back out of mount. Considerable force needed.
19. Put plastic washer on piston. Do not install old bump rubber as Bilstein strut has built-in bump stop.
20. Put dust cover back on.
21. Push strut in mount and tighten 22 mm nut. Hold large washer to tighten nut.
22. Re-install brake lines and put wheels back on.

Then I did the rear ones. These are real easy.
Jack up the car, put on jackstands and remove the wheels. Take of the air filter cover and air filter to be able to reach the right upper nut. Take off the upper nut (17 mm) in the engine compartment. Difficult to reach, but it came off by using a flat impact wrench. Then take off the large nut (22 mm) at the bottom of the strut. I needed a strong impact wrench for this one. Hold the strut before the bottom bolt comes out, or it will kaboom on the floor. Install the new strut by reversing the procedure.

After installation, my car sat quite a lot higher on its wheels, especially in the front. The shocks settled when I took the car for a spin, and now it seems that the front of the car still is about 0.5 inch above its original ride height. I will see what happens after I drove it some more, and adapt the ride height when necessary.

JonH

Nice write up Celle, I've got KYB's on the back of my '74 I think I'll switch to the Bilsteins next around. Question also for you, I've got rubber bushings on the lower rear shock that are larger than I see on any other 911, what is the correct bushing/washer that goes between the lower shock bolt and the trailing arm, is it any special part or just a large washers?

Celle

John, it's just a large washer on the side of the bolt. I used the original one along with the original bolt. There weren't any bolts or washers with the new shocks. Does this answer your question?

Celle

I just noticed that I wrote "nut" for the bottom fastener of the rear shocks. This actually is a (pretty long) bolt that goes through the bushing at the bottom of the shock and into the trailing arm.

JonH

cool, that's what I thought. The previous owner must have put these larger rubber washers on. Thanks,
Jon

Peter Zimmermann

Don't forget, before you torque (90 lb/ft) the lower, rear shock bolts, that you jack up the rear wheels to something close to driving position. Then torque the bolt and lower the wheel/suspension. If you don't do this there will be pre-load against the lower shock bushing - which you don't want.

Amber Gramps

I gained 1/2-3/4" in rear ride height with the install of BHD's that drasticly changed the rear camber and really put a lot more rubber on the ground. I would say it restored the car to original ride height.