Performance Car Suspension Tuning | Improve Car Handling

Car Suspension Tuning for Improved Stability

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Suspension Tuning

Here we believe in tailoring your vehicles tuning to your specific needs.

We are aware that every customer has different demands on there vehicle so the tuning packages are more to give you an idea of what can be done to the vehicle. And not a strict guide line to follow.

Chasis Tuning Technical information

Purpose of suspension

Suspension by definition means the vehicle is riding or hanging on something with give. It has to have some flexibility and over the years a great deal of ingenuity has been expended on a wide variety of materials and methods of employing them. Mounting the axle directly to the frame of a vehicle would subject the occupants and general components to severe shocks. It is known that when a wheel strikes a bump the vertical acceleration will cause considerable shock, this is because the vehicle chassis can not move upwards quickly enough and without suspension the inertia would probably buckle the wheel (you can observe this situation when riding a unsuspended bicycle over a bump).
A spring fitted between the wheel and the vehicle chassis allows the wheel to move up and down without causing similar movement of the chassis. The spring will absorb road shocks and allow the wheel to follow the irregular contour of the road surface: for this purpose the wheel assembly should be as light as possible.

Coil Spring

The coil spring has many virtues, it is light, compact, inexpensive, variable in length, rate and diameter, friction free and there is a mass of knowledge concerning its manufacture and use. The spring is usually made from high quality round steel bar with an extremely accurate outside diameter. Heated, the rod can then be wound into equal coils, tapered, given varied diameter on the coils all to achieve different results in use. Final heat treatment gives it extreme resistance against failure or deformation in use.
This spring is often used in conjunction with independent suspension, front and rear, although the absence of interpolate friction has prompted some manufacturers to use it at the rear with a dead axle. Coil and torsion bar spring are superior to leaf spring as regards to energy storage (energy storage in a given weight of spring). The rate of the spring is governed by the length and diameter of the wire and the number of active coils.
Coil springs are used on literally millions of road cars and race cars, on road cars they are mainly used on the front in McPherson strut designs and on the rear with a Dead axle or rear trailing arms, on sporty models they may be used in conjunction with a rear anti roll bar to prevent body roll.
On race cars they are used in many different configurations the main one being the double wishbone design and adaptations of this.

Purpose of a damper

When a wheel strikes a bump energy is given to the spring, which is deflected. When the bump is passed, rebound or release of the energy will take place, and will carry the spring past the normal position to set up an oscillating motion. This action is similar to the action of a pendulum - a freely suspended pendulum will oscillate for a considerable time after being struck.
In order to give a comfortable ride, some device must be fitted to absorb the energy stored in the spring and so reduce the number of oscillations occurring between the initial bump and the return of the spring to the rest position. This is the duty performed by the damper.

Some suspension/chassis tuning terms explained

Castor

Caster is the side view of the Kingpin axis. It is the inclination of a line drawn through the ball joints. Usually the line slants toward the front of the vehicle. This also relates to stability.

Camber

Camber is the inclination of the tyres from vertical, as viewed from the front of the tyre. Camber is measured relative to the ground, not relative to the chassis. Positive camber means the top of the tyre is leaning away from the chassis, negative camber means the top of the tyre is leaning towards the chassis.

Kingpin inclination

The kingpin axis is the line drawn through the upper ball joints, as viewed from the front. A positive kingpin axis is inclined toward the tyre at ground level. The lower ball joint is closer to the tyre than the upper ball joint when the Kingpin axis is positive.
Most vehicles have a positive kingpin axis in order to provide a cantering effect in steering. With a positive Kingpin axis the chassis is at its lowest point when the steering is straight forward. Thus the chassis seeks to return to zero steer after steering movements.

Centre of gravity

The point at which the whole vehicle would always stay perfectly balanced whether on its side, nose or even upside down. This is Difficult to locate precisely but close estimates are practical.

Spring rate

The load necessary to deflect any spring by a given distance, Lbs/in or Newton's/mm.

Wheel rate

This is spring rate as seen by the wheel after the suspension leverage effects.

Sprung weight

This consists of parts of the vehicle supported by the springs. Generally taken as gross weight, less un-sprung weight.

Un-sprung weight

This is normally taken as wheels, tyres, hubs, outboard brakes E.T.C. plus half the weight of any of the linkages, outboard coils/dampers.

Roll centre

The roll centre is an invisible moving point about which a vehicle is considered to rotate in a corner. This is easy to plot in a static situation, but far from easy once the vehicle is moving.

Weight transfer

Lateral weight transfer is caused by cornering forces which transfer weight across the car towards the outside of the turn direction and away from the inside of the turn direction. The transfer of weight increases the vertical load to the outer tyres by subtracting some of the vertical load from the inner tyres.
Normally vertical load is good for tyres as it increases grip available for cornering. In the case of increased vertical load caused by transfer, however, the physics of the tyre performance ensure that amount of lateral grip added to the outside tyres is less than the amount of lateral grip removed from the inside tyres. Thus, the overall effect is a loss of lateral grip just when you need it most.
One way to increase cornering performance then is to minimise lateral weight transfer and so reduce that portion of the vertical load that is transferred from one side of the car to the other.
In this situation it is only these cornering induced transfer loads that we want to reduce and not any net additional vertical load gain from aero down force. Aero down force adds vertical load roughly equally to each side of the car and this increases the amount of lateral grip available from the tyres. It is important to understand net grip gains from down force via aero effects versus the net grip losses from load transfer during cornering.
The cause of the cornering that leads to the loss of grip is, that the track turns away from the straight and the car must turn with it and follow the road around the corner.
On the majority of the world race circuits you have to turn a full 360 degrees more in one direction than the other to arrive back at the start line. In doing so the car is naturally forced to undergo more undesirable lateral load transfer in one direction than in the other. If all the turns were to the left it would be possible to reduce the amount of lateral load transfer by the simple means of pre shifting the cars static weight distribution in the same direction, in other words to counter the left turn induced lateral load transfer you would start out with more of the cars weight already shifted towards the left hand side of the car.
With the weight so moved the car would still suffer lateral weight transfer during left hand turns but this would have the effect of moving the weight back towards the centre of the car. Thus the lateral grip loss caused by load transfer to the outside of the car would be reduced, enabling a higher cornering speed.

Chassis Common Problems.

This car is over damped. Dampers are too hard

Too much rebound damping

Too much bump force Too much bump damping

Too much low piston speed bump damping

Too much high piston speed bump damping

Low speed bump damping too harsh.

Too little shock All round soft suspension

Low spring rates

Too little damping

Too little rebound force

Too little bump force

Too little high piston speed bump force

Too little low piston speed bump force

Front toe-in - too much

Front toe-out - too much

Rear toe-in - too much

Rear toe-in - too little

Rear toe-out

Front wheel caster - too much

Front wheel caster - too little

Steering effort harder in one direction than in the other
Car pulls towards wheel with less caster

Front wheel caster - uneven

Inside of tyre excessively hot or wearing too rapidly. At the front this will show up as reduced braking capability and at the rear as reduced acceleration capability

Camber - too much negative

Camber - too much positive

Bump steer front - too much toe-in in bump

Bump steer front - too much toe-out in bump

Bump steer rear - any toe-out in bump

Roll axis too far out of parallel with mass centroid axis leading to non-linear generation of chassis roll and lateral load transfer; the tendency will be toward too much load transfer at the rear, which will cause oversteer

Rear roll centre too low - or front too high

Opposite of above, tending toward corner entry understeer and three wheeled motoring on corner exit

Front roll centre too low - or rear too high

Car tends to trip over its front feet during slow and medium speed corner entry
evidenced by lots of understeer. Quick fix is to increase front ride and roll resistance and to raise front roll centre

Front track too narrow in relation to rear

Harsh ride; excessive wheel patter, sliding and wheel spin
High temperature reading at centre of tyre

Too much tyre pressure

Soft and mushy response
High tyre temperatures, with dip at centre of tread
Reduced footprint area and reduced traction

Too little tyre pressure

Gradually increasing understeer

Front tyres 'Going Off'

Gradually increasing oversteer

Rear tyres 'Going Off'
Drags inside rear, which reduces corner entry understeer
Increases corner exit oversteer

Inside rear tyre larger diameter than outside (reverse stagger)

Also See Performance Car Tuning

Also See Breaking Upgrade Tuning

Also See Transmission Tuning

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sales@solware.co.uk or Tel 0844 357 0306

Also See - ECU Maptune - Power, Breaking, Transmission and Chasis Tuning - Specialist Car Servicing - Custom Engineering

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