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Old 03-24-2011, 08:45 PM
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Aussie Mike Aussie Mike is offline
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Join Date: Jan 2001
Location: Sunbury, VIC
Cobra Make, Engine: Rat Rod Racer, LS1 & T56
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Here's how I like to think about it...

The spring's job is to keep the car off the road and keep the wheels in contact with the road. Like any spring the energy of your cars movement will travel back and forth along the suspension spring. The damping in your shocks stops this energy moving back and forth by dissipating it through a controlled resistance (oil moving through an orifice). That's their basic job. The heavier the vehicle the heavier the spring required to support it and the stronger the resistance required to damp the springs oscillation.

Cars being a machine that likes to change direction accelerate and generally carry on means that the weight carried by each corner of the vehicle changes due to the cars inertia. The shocks adjustability lets us have some control over how quickly that weight moves from corner to corner.

Shocks usually have damping that works in both directions of travel.

Compression damping is the resistance to the shock compressing i.e when your suspension loads up.

Rebound damping is when the shock is relaxing or when the load comes off the suspension.

A Single adjustable shock has one knob that changes the overall resistance of both sides (compression and rebound). A double adjustable usually has two knobs that let you adjust the resistance levels of the compression valve and rebound valve separately. It's usually done by changing the size of the orifice the oil is forced to travel through.

Most non adjustable shocks are fixed from the factory with 50/50 each way i.e the same resistance in both compression and rebound.

As basic example of how shocks can be used to move the vehicle weight to where it's wanted, drag racers often like running 90/10 shocks on the front. That's 90% compression damping and 10% rebound damping. They do this to help move the vehicles weight onto the back wheels. As the car accelerates the front lifts. The 10% rebound damping allows the front suspension to easily relax and the front quickly rises. That moment of instant acceleration passes and the car starts moving down the track but the 90% compression damping slows the rate at which the front suspensions settles and keeps the front up in the air and the weight on the back wheels.

In a Cobra the loads are not only in acceleration but lateral cornering loads and deceleration. So under brakes the weight transfers to the front and in the corners it transfers to the side. The load is usually greatest when the car is first thrown into the corner so increasing the compression damping on the outside corner will slow the rate at which the suspension compresses on one side keeping the vehicle's weight on the other tyres. Increasing the rebound damping on the suspension on the inside wheels slows the rate at which the suspension relaxes and keeps the weight on that side of the vehicle.

This is a very simplistic view but it helps me understand what's happening.

Cheers
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Mike Murphy
Melbourne Australia


Last edited by Aussie Mike; 03-24-2011 at 08:50 PM..
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