Suspension FAQ

Spring function

A spring is used on each corner to support the weight of the car and mainly absorb vibrations from the road. Dampers will usually have little effect on ride height of a vehicle.

Damper Function

A dampers purpose is to control the movement of the spring. It does this by taking the kinetic energy in the spring and converting it to heat energy via hydraulic resistance, this is then dissipated to the atmosphere via the damper tube. For this reason, heat management becomes a very important factor in competition applications. Without the damper, the spring would continue to oscillate.

Stainless steel tubes

Stainless has become popular by KW for damper production recently due to the corrosion resistance properties. This is a good benefit for a road going suspension kit but it does come with sacrifices. The material is more brittle than steel so tube and mount thickness need to be increased which increases weight when compared to an equivalent steel unit. This adds to the un-sprung weight and mainly as explained above a damper converts energy from kinetic to heat, with a thicker walled tube the heat is retained in the unit for longer making it less suitable to track day or competition purposes.

Wall thickness

Upon analysis, we found many units from the eastern side of the world using the same wall thickness tubes on a MacPherson strut as most damper manufacturers would use on the rear dampers and seeing failures. Suffering this sort of tube failure is unacceptable to us and we’ve made sure all of our MacPherson struts have a thicker wall to avoid the failures seen on the more cost effective units.

Strut length adjustment

Strut length adjustment is a useful feature we like to implement in our kits. This allows you to set the damper length to suit your requirements. The plus side is it can cater to nearly everyone’s wheel and tyre combinations, but the downsides are due to this the bodies need to be shorter which loses oil capacity and the dampers ability to manage heat efficiently, each of our kits are designed to retain the largest damper body possible unless asked otherwise..

Damping adjustment

Everyone has different perspectives as to what performs and feels right for them. Road going suspension is particularly hard to tune as ride quality is very much subjective but a substantial factor. Some people may be happy with a certain kit only for others to find it too soft or a bit choppy at low speed.

Most of our kits offer at least 1-way damping adjustment giving you the ability to tune the ride and handling that suits you, your car and its application. This becomes particularly useful for dual-purpose cars doing the occasional track day. A quick change in damper settings can give good results and easily put back for the drive home. More serious applications may want to go as far as swapping springs before events.

Each damper manufacturer offers different adjustments and ranges but be aware of what the adjustment is actually doing.

1, 2, 3 or 4 way damping adjustment

A 1-way damper will adjust any combination of the 4 usually found parameters, high and low-speed compression and rebound, usually them all. Sometimes just rebound and some are mainly low speed compression and rebound.

A 2, 3, or 4-way damper offers any combination of the 4 parameters individually adjustable. This can be a valuable tuning tool for tuning race car dynamics including spring rate changes but extra variables can give more of a chance for incorrect settings if they are not understood.

Most 2 ways will offer compression and rebound damping independently and a 3 way usually offer high and low speed rebound joint with high and low speed compression independently.

Air suspension

Pneumatic springs are an in-car adjustable progressive rate spring that can offer huge versatility, allowing in car height changes or load carrying abilities. All of our springs are dyno’d at various pressures with our rate testing machine and each application is matched to volume, clearance and the weight of the car. Our GT and Clubsport kits will come with various recommended air pressures and damper settings in the instruction manual for your kit.

For performance applications, the adjustment is in the opposite direction to what you’d usually require. The lower you go the less pressure and therefore spring rate the bags have. Our kits run shortened length adjustable dampers allowing you to set the pressure you prefer and use the adjustment to give the desired height range. For a dual-purpose track day setup, you can shorten the strut, run a higher pressure, adjust the damping and put it back for the drive home.

The air spring offers less structural rigidity when compared to a conventional steel spring, putting more stress on the damper shaft in cars with a MacPherson strut reducing longevity. For performance applications, a double piston is a standard feature on the Rennsport Factory Clubsport kits. This gives the shaft an extra bearing offering near inverted strength without the additional friction.

Coilover

Spring sits over the damper. Usually featuring height adjustable spring perches.

Inboard spring

Spring that sits next to the damper.

Spring rate

Amount of force needed to compress the spring a given distance.

Height adjustable

The spring perch has the ability to move up and down allowing you to set your own ride height.

Strut length adjustable

The ability to shorten or lengthen the entire shock body.

Inverted damper

Damper shaft appears to be 40mm or more in diameter. The damper is actually upside down and runs on PTFE lined bushes inside the casing with a smaller rod located inside the main casing. This offers increased strength in MacPherson strut assemblies at the downside to increased friction.

MacPherson strut

This is when the damper is used as an integral link in the suspension and the steering pivots around its top mount..

Chapman strut

This is when the damper is used as an integral link in the suspension but the steering does not pivot.

Double piston

Our double piston gives the damper shaft an extra guide for increased strength in MacPherson strut assemblies. With our custom oil seal this is nearly as strong as an inverted damper but without the additional friction.

Digressive valving

This allows a large build-up of low-speed force to control body movement whilst allowing the high-speed movement to “blow off” at a certain piston speed, reducing the harshness of high-speed damper events such as potholes or race curbs. We apply this to the compression of our road going suspension kits.

Linear valving

This will have less damping in the low speed area as the valving increases in a more progressive manor. When looking at the valving on a graph, post “knee” the valving will continue to increase in force whereas the digressive valving will not continue to increase.

Compression damping

The damping force slowing the spring in the downwards motion.

Rebound damping

The damping force slowing the spring in the upwards motion.

Knee

The point where damper changes from high to low speed damping.

Low speed damping

These are the when the shaft is moving at slower speeds, like a change of direction.

High speed damping

This when the shaft is moving at faster speeds, irrelevant of the speed of the car, these are the potholes, kerbs and sharp jolts.

Adjustment positions

The number of adjustment settings each damper has. More doesn’t necessarily mean a larger range of adjustment and a large range of adjustment has its downsides when tuning the damper.

CNC

Computer numerical control, an automated machine tool controlled by computer to fabricate nearly any part.

Critical damping

100% critical damping means the spring in only allowed to oscillate once.

RSF Nitron NTR R1 1 way damping and height adjustable coilover or inboard suspension kit
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