Suspension Modifications

After driving the car at a few autocrosses, I came to the conclusion that the suspension was too soft for my liking. The original shocks were still on the car, and I assume most if not all of the rubber bushings were the originals as well. Since the car was going to be used primarily as a weekend and track car, I decided that the suspension needed an upgrade.

When it comes to modifying suspensions, I believe that if the springs are replaced with a stiffer set, the shocks should be changed at the same time to a shock that is valved to match the spring rate. The stock torsion bars on a 86 to 89 Carrera are 18.8mm front, and 25mm in the rear. I replaced these with hollow bars from Sander Eng. sized 23mm front, 30mm rear. To keep pace with these rather large bars, I choose the Bilstein sport valved shock.

These are torsion bars from Sander Eng. I choose Sander mostly because they were recommended in Bruce Anderson's "Porsche 911 Performance handbook". The splines are apparently a better match to the factory spring plate than some other bars. Bar sizes are: front: 23mm rear: 30mm

While adding the new torsion bars and shocks, the ball joints and bearings were also replaced as preventative maintenance. My mechanic and I also thought that since the suspension was already apart, we may as well do some bushings. Entirely new A-arms were installed with new bushings, and the tie-rods were replaced with turbo tie-rods, but the big step came when I decided on using monoballs! The large rubber bushing at the top of the front shock was replaced with a monoball from "The Pivot Group" while the rear banana arm bushing was replaced with a monoball from "Smart-Products". Here is a link to an article written by a friend of mine about the installation of these monoballs on his car.

Here are the monoballs for the front and rear of the car against a ruler to show size. The rear monoball consists of two of the cones shown here, and a outer sleeve (not shown) and retaining clips.

This is a picture of the all of the parts of the rear monoball.

I ordered adjustable 22mm swaybars from The Racer's Group, and they will be installed in the spring of 2001. I will also have to get my rear swaybar mount reinforced so it doesn't break, which is a common occurance on the track driven Carreras with stiffer swaybars .

Here are 22mm "The Racers Group" sway bars fresh out of the box. I choose these over other brands because I liked the hardware and contruction quality of the parts. The adjustability will be a nice feature to have, so I can remove some of the oversteer I have in the car.
	This the front sway bar installed. The marks on the arm are from the drop link slipping during a track session. I hadn't done the bar up tight enough and it was slowly moving during the day, and the car was moving more towards oversteer as the day went on. I thought my tires were getting to hot or something. I found the moved bar when I got home. I do it up a lot tighter now :)
Here is the rear sway bar installed. Those with a keep eye may look at the front setting and the rear setting and figure the car understeers like a pig. Actually, the rear bar has not been set to it's track setting in this picture, where as in the top picture it has. These things are probably one of the best improvements I have made to the car. The adustability is so nice to have to set the car up with a neutral balance.

For a strut brace, I decided to go with the Camber Truss that triaglulates the struts to the floor of the trunk. Since this car is a targa, it can use all the help it can get with stiffening the chassis.

Once these parts were on, it was time for an alignment. Once again, I asked around to see what specs have worked for different people and the final settings are as follows:

As you can see from the above table, some of my alignment settings are out of spec with the factory. I choose these particular settings to make the car a good track and autocross car, while still being able to drive it on the street without the car being "twitchy", or having to replace tires every few months because of excessive negative camber. The 0 toe up front, in combination with the monoball suspension and low profile tires give the car excellent turn in. The rotation of the car around the corner is excellent, and when it hooks up in a corner, it feels like it is on rails. Adustable sway bars helped balance the car to just the way I wanted it. If you are planning on modifying your 911, the sway bars are a must.

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