The Benefits of Uprated Performance Suspension over a cars Standard Set Up. Weight Transfer. The speed at which tires load up. Weight transfer occurs during all manoeuvres ie braking, acceleration and cornering. It is the job of the car suspension to control this weight transfer, in other words to keep control of the body of the car and to keep the tires in contact with the road. The original equipment shocks and springs supplied by the car manufacturers is more often than not a compromise between good bump absorption, to keep a comfortable ride, and road holding. This is to keep production costs down. With aftermarket performance suspension kits there is usually a strong relationship between maintaining ride comfort and price. ie the more expensive the suspension kit (such as Bilstein, TEIN and H&R) the greater the cornering speeds with very small reduction in ride comfort. Some cheaper suspension kits (Apex, Spax & G Max) may increase handling but the ride comfort is noticeably compromised. Each manufacturers make their kits differently you should research each manufacturers products against your own preferences to determine what sort of ride your willing to live with against the sort of handling increase you want to achieve. The next section highlighted the various situations that are encountered on day to day driving and compares the differences that can be expected between the standard springs and shock set up and an uprated suspension kit/coil over suspension kit. The severity of each situation will vary widely depending on the car for example an BMW M5 at 130mph will feel much more stable that a Ford Fiesta at 130mph. Disclaimer: The information in this article is purely the opinion of its author and no responsibility whatsoever will be taken from alleged or implied injury or loss caused by reading this article. Any queries regarding this article should be directed towards a suitably qualified mechanic. All uprated/sport shocks and spring kits should be fitted by a suitably experienced and/or qualified person. Situation High Speed Straight Line Instability. The car has a floaty feel. Steering may feel "light" Standard Suspension Assuming a normal motorway surface (quality road). The spring movements are quite small. The spring is moving an insufficient amount to fully utilise the shock absorber ie movements are not properly damped. The main contributory factors to this situation are the low weight of the car and the lift created by the car body at speed. Uprated/Performance Suspension Kit Although a lot of the factors contributing to this situation are not suspension related, a higher spring rate and bump and rebound rates found on shock absorber found on performance suspension kits will greatly reduce this condition, making the car feel more "tied down" and stable. Instability through high speed corners. Assuming the road is relatively flat. This is perhaps the most obvious sign of instability or insufficient control of the cars body movements in relation to your driving style.   Initial instability on turn in, and then general instability through the corner. The standard springs and shocks will take longer to settle than a performance suspension kit. As the speeds are higher a greater distance is travelled before the car settles. this can lead to a kind of leap of faith situation where you commit to a corner and having to wait for the suspension to stabilise the weight transfer and tell you how much grip is available. Uprated shocks and springs increase the speed of weight transfer which means that the delay between committing for a high speed corner and the tyres telling the driver how much grip is available is smaller. Depending on the car, the performance suspension kit fitted and the corner, the difference could be between 2 tenths of a second to 2 seconds. At speeds over 80mph this can mean that big distances are covered before the tyres are fully loaded up. The higher the speed of the corners and the softer the springs and shocks the greater the leap of faith. All in all Uprated suspension will provide the driver with a higher level of confidence at high speed. Combine a high speed corner with a lane change If the driver is committed to a corner and a sudden lane change is required a very unstable situation can follow. This is especially true if the lane change is required in the very early stages of the corner where the springs are not fully loaded up. The shocks and springs will have very little control of weight transfer at this stage and this can lead to an unstable situation Although this situation can lead from a driver over committing to a corner ie driving to fast an uprated suspension set up can help the driver maintain full control and provide the driver with more options with regards to evasive action. Uprated shocks and springs will keep tighter control of the weight transfer meaning that more grip is available for more of the time. Low Speed Corners. Body Roll Body roll can be very pronounced in some cars when negotiating tight corners. This can be uncomfortable for both passengers and driver especially if the seats in the car are not supportive. Uprated shocks and springs will keep the car flatter through tight corners making for more comfortable progress. As a secondary measure Anti Roll bars can also help reduce this problem. Level of grip. Standard shocks and springs by their very nature are softer than a uprated suspension kit. This means that the wheels will have more vertical travel. The more travel the suspension has, the harder it is for the tyres to maintain a consistent and large contact patch with the road. The camber of the wheel will change, depending on where it is in its field of travel and how much force is being exerted on it. Coil over kits and uprated shock and spring kits allow less travel enabling the tyre to have a larger contact patch with the road more of the time, compared to the standard set up ie more grip. With reduced suspension movement the camber and castor of the wheels will not change as much. Ride Comfort How can coil over kit or any uprated shock and spring set up come close to the ride offered by the standard set up? At normal driving speeds the uprated springs and shocks or coil over suspension kit can be made to be nearly indistinguishable from the standard set up. Performance shock and spring kits can be made to be as bump absorbent as standard suspension in the early stages of travel. ie over small bumps and cornering where the forces aren't high. This is done by utilising progressive springs (Eibach, H&R for example). These springs move as normal springs where the forces are low but when they are leaned on, the spring rates increase. The more they are compressed the stiffer they become. If uprated shock and spring kits are so good why don't the car manufacturers fit them as standard? Cost. The majority of drivers may not even approach the limits of their vehicle for the whole time they own it. Although the car manufacturers could up rate the shocks and springs, the cost of doing is not justified as most drivers would not know the difference. This is especially true on non performance models. I have a performance car, the shocks and springs are already uprated why will fitting an aftermarket uprated suspension kit improve the handling? Again the answer is cost. If you are looking for out and out performance coil over suspension or a high quality shock and spring combination is the only way to go. These performance units are prohibitively expensive to be used on all but the most focused and well sorted performance cars, this cost cannot be justified by the car manufacturers for the little if anytime they spend at their admittedly higher limits. It should be noted that if your car is already a high performance model it may well be worth going for the premium end of the aftermarket suspension kit range (Bilstein, TEIN etc..) as anything less may be a backwards step over the car manufacturers original equipment. The Renault Clio Trophy and Subaru Impreza STI being cases in point. All aftermarket uprated shock and spring kits should be fitted by suitably qualified/experinced person to ensure the full benefits of the new setup can be realised. For example camber and castor angles may well need adjusting especially if the performance suspension kit fitted lowers the ride height of the car. You should only take your car to the limit if you are confident in doing so and should be only attempted in a safe and controlled environment such as a Race Track or Airfield. The increase in handling and cornering forces will vary widely from car to car and on the age of the car. If you believe your car has exaggerated body movements and does not exercise proper control of the vehicle you should get it inspected by a suitably qualified person immediately.