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Last Updated: 18 June 2013 18 June 2013
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SuspensionThe Porsche 928 can suffer a multitude of suspension problems that basically stem from 2 factors. Firstly the car is heavy - most 928s weight over 3500lbs. Secondly most 928s are now relatively old cars - all are over 15 years old.

The symptoms of problems are:

A correctly setup 928 should not hit the ground or float - in fact the handling should be very tight and surefooted. These problems are caused by any one - or indeed any combination - or even all 3 - of the following causes.

928.org.uk recommendation

aim for 175mm front and rear. This is within the factory specification and will result in a very slight nose down stance. This article explains how, one of the earliest articles from the information base on the site.

A heavy sports car driven fast is going to make huge demands on its shock absorbers. Like all components shock absorbers have a limited 'life' after which there effectiveness weakens to the point that they should be replaced.

There are several options. If you don't intend driving your car hard then the standard shocks are totally acceptable. However if you want to push your 928 hard then nothing beats a set of sport shocks. This will give any 928 "SE/GT" standards of handling - with the downside of a more controlled ride which some might find unacceptable. For those that wish to adjust their setup then the ultimate option is a set of externally adjustable Koni shock absorbers.

As the 928 is so heavy its springs will gradualy sag under the weight and hence the cars ride height will lower. Whilst some like the lowered look there is no doubt that it brings the underside of the car nearer the road surface!

The inevitable result is that the underside of the car is far more likely to hit the road under extreme body movement because of fast driving or a very uneven road surface. In fact it can lead to speed bumps being impossible to drive over without scrapping the underside of the car. Not only does this cause a horrible noise but components of the car are damaged. The air conditioning is particularly vulnerable on all cars - as are front spoilers. S4 and later models are vulnerable to severe damage to their under engine belly pans.

The solution is to raise the car to its correct ride height

Sportier drivers may also wish to fit new springs or upgrade them to Club Sport specification (ie 10% stiffer at the front) or even fit aftermarket springs like those available from Eibach for the 928.

Suspension Sag

A common problem with 928s is "suspension sag". This is caused by the following factors:

Sag leads to the following problems:

Porsche specified ride height

The following specifications are taken from the Official Porsche 928 Factory Manuals:

Tools

To change the ride height you will need the following tools - besides plenty of time and energy (its an exhausting job):

rhneed.jpg

Procedure

Step 1. Measure

First park the car on a completely flat surface. A level double garage floor is ideal, provided there is enough access around the whole car.

Step 2: Adjust

Front Rear
rhfsusp rhrsusp
Front Rear
rhfspan rhrspan

Step 3: Settle

When the car is fully adjusted you will notice that it sits very high. This is because the 928 suspension takes time to settle to its actual ride height. Therefore the suspension must be forced to settle before the height can be re-measured and checked.

Front Rear
rhfpre rhrpre

Step 4: Repeat Until Correct

Note:

Some procedures call for the wheels not to be removed and the car not to be jacked up. This does mean that the height can be re-measured straight away without a drive, removing the wheels; and could be quicker. However, the notched nut is difficult to move (especially on the front) and we recommend this procedure to get the necessary leverage required.

FRONTrhfpoint

REARrhrpoint

The measuring point is directly behind the centre of the wheel hub, where the suspension attaches to the car. (For S4 and later cars it is just in front of the under belly pan - as can be seen at the upper left corner of the picture above).

The actual point is the flat machined surface between the two flanges and two bolts. You should be able to hold the strip of wood vertically between the ground and the machined surface with a few mm to spare (for a 175mm front ride height).

The measuring point is located at the end of the horizontally "U" shaped suspension arm, where it is attached to the car.

The actual point is the small raised flat surface. You should be able to hold the strip of wood vertically between the ground and the machined surface with a few mm to spare (for a 175mm rear ride height).

Author Andy Elvers