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Ask Ollie – Suspension basics explained

Over the past few weeks we have had a fair number of customers wanting to learn more about the suspension aspect of their cars. When customers book themselves in for a geometry setup (Geo) on their car, they know it feels better once the job is completed but don’t really know why. We issue before and after print outs, in order that they can see where the differences have been and this got us thinking that we could do the first of a ‘Technical Blog post.’ We have written down the basic common terminology used when referring to geo’s and how they affect your car. We hope you find this useful:

Camber

Can be discussed when talking about both front and rear of your Porsche, and is simplistically described as the vertical angle of the wheel. Most common descriptions a technician will talk about are either ‘positive’ or ‘negative’ camber, measured in degrees off of a totally vertical wheel at 0 degrees.

Negative camber is what you would see on a race car, whereby the bottom of the wheel is further out than the top of the wheel. Positive camber being the opposite. The logic in running negative camber would be to increase tyre footprint into the road/track when the car is being driven fast, along with creating a shaper response to the driver turning the steering wheel. The negatives of this would be too much and the car will feel too nervous and or increased tyre wear. Its unlikely you would ever see a car running positive camber as this would only be used on off road vehicles or similar, so we won’t go into the explanation of this.

Toe (also known as tracking)

Again can be used to describe both front and rear of the car. The toe is the angle of the wheel when seen from above (ignoring steering input) again measure in degrees, referred to by technicians as ‘toe in’ or ‘toe out’. Toe in would be with wheels pointing towards the body of the car and toe out the opposite. The benefits of running with ‘toe in’ would be more aggression on turn in but with the down side of increased tyre wear and increased drag as the tyre is effectively scrubbing itself while driving in a straight line.

Castor

Is the angle in relation of the top and bottom of the wheel so 0 degrees camber would straight up be like a shopping trolley, easy to move side to side but no “feel” and very nervous at high speed (ever been down a hill in a shopping trolley!) or self-centring think about the angle of the forks on a push bike and the feel you get when riding the natural fore of forward motion pushes the wheels straight.

 

The art of getting the car set up is the combination of all of the above in relation to the use of the car. The configuration of the car (front, mid, rear engine) along with plenty of other inputs such as ride heights, spring and shock absorber set up, bushing etc. The combinations are infinite!

If you would like to discuss getting your Porsche set up, please contact our Technical Director Ollie Preston who would be happy to help.

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