Handling/Shock absorbers
Introduction
Although simply
lowering your car is an effective way of improving the handling characteristics, a lot more improvent can be achieved by installing performance shock absorbers. These are generally stiffer, shorter, and have a longer life span than the stock shock absorbers. Performance shock absorbers come in many variations. The cheapest ones simply replace your stock suspension, the more expensive sport kits are adjustable. Shock absorbers that contain a fluid with magnetic particles which can be adjusted "on the fly" electronically are also being used in modern sports cars and GT's.

The inside of a fluid shock absorber
The perfect tradeoff
When it comes to performance on the track, the rules are quite simple: the stiffer, the better. It is however more likely that you'll want your car to be useable on the road. Good news is that both the entry level shock absorbers and the more expensive kits will allow you to do so at a relatively low decrease in comfort. This is partly due to the fact that they are usually constructed in such a way that small bumps are still filtered out almost as much as stock absorbers, or in other words: because their behaviour is progressive.
When set up to be quite soft, a sport shock absorber will not cause any problems in normal road use.
The next question is of course what kind of kit you are looking for. Simple replacement shocks will not cost you much more than stock parts. A full sports kit (lowering springs+ adjustable shock absorbers) will do about $500 to $800.
A fully adjustable coilover suspension kit which allows for the fllowing to be adjusted:
- Ride height
- Spring stiffness
- Inbound shock stiffness
- Outbound shock stiffness
Will cost about $800 to $1200. This is a lot of money, but a very good investment if you intend to use your car on a racetrack.
Front and rear coilovers from KW
Does the car's grip improve by installing new shock absorbers.
Not directly, like lowering springs, stiffer shock absorbers keep your car in a better balance, causing less unexpected under- or oversteer while cornering, braking, and accelerating. Where cornering quite fast over an unexpected bump or dent with stock suspension causes your car to wobble or break out, a stiffer suspension kits keeps your car in a straight line, and even if it decides to throw it's rear out, correcting the situation will be a lot easier and safer. Steering input response is usually also more direct with stiffer suspension.

The koni sport kit, one of many kits which offer adjustable shock absorbers combined with lowering springs. Generally these kind of kits provide best value for road going cars.
Effect on steering behaviour
One thing that is not very often mentioned is the effect of front and rear stiffness on oversteer and understeer behaviour. Although understeer and oversteer depend on a lot of variables, like wheel alignment, steering input, weight distribution, etc. the general rule of thumb is that having a stiffer rear suspension and softer front will increase oversteer and vice versa. This is something that you will have to tweak to your car, and your personal preferences. I have set up my own car to be almost completly neutral(just slightly oversteering) when not accelerating or braking by setting the rear shock absorbers in 1/2 of the maximum stiffness and the front at about 3/8.