Suspension Setup Information – Set Up & Evaluation of Performance Suspension Kits.
Smithees Race Car Technology
Technical article covering suspension
Sun 3D Wheel alignment for street, drifting, rallying and circuit racing.
E30 M3 Performance
Site is dedicated to the E30 M3 but has technical articles which can be applied to most cars. Subjects covered include splitter theory, driving position suspension set up and roll bar set up and effect. A worthwhile read.
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 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.
High Speed Straight Line
Instability. The car has a
floaty feel. Steering may
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
f 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.
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
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
Basic Driving Techniques for Front Wheel Drive(FWD) Cars.
Disclaimer: All cars handle differently depending on their model, age and condition. This information should be used as a guide only, no responsibility will be taken for injury or loss which is alleged to have come from this article. It is up to the driver to drive in way he or she feels comfortable with and in a manner that is consistent for the road conditions and the capabilities of the car.
FWD cars put all of strain of the front tyres. The front tyres have to steer the car as well as drive and do the majority of the braking. The guide focuses on giving the front tyres the best possible chance of giving their best grip in all situations.
Braking: Should be carried out in a straight line where possible, although this is true for most cars, it is especially true with FWD. By doing all the braking in a straight line the tyres can give maximum grip to steering the car. This technique may take time to get used to, but it can be used everyday and will lead to faster and safer progress as well as giving increased comfort to passengers.
Acceleration Out Of Corners: As the tyres have to steer as well as drive the car by accelerating in a straighter line as possible ensures that the tyres can donate more of their grip to driving the car forward. In effect this means utilising a slow in, fast out cornering technique. The more of a corner that can be taken when accelerating the better the speed on the next straight. In practice this means taking a late apex.
Understeer: Depending on the car this state can vary widely. Newer Front Wheel Drive Cars resist understeer well. If understeer is experienced lifting the throttle should give better grip to the front tyres and increase cornering efficiency.
Oversteer: If the car enters an oversteer phase then accelerating will increase grip to the rear tyres and therefore limit the slip angle.
In oversteer situations the driver should always look in the direction that they wish to proceed even if this means looking out a side window.
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