TECH > SPRINGS AND COILOVERS BASICS  
   

 





 
Springs and Coilovers Basics
The most popular and important suspension modifications.

 

 

Progressive Springs:

This is the best choice when on budget and yet you want to improve the looks of your car by lowering it and make it handle better.

For the above purpose, the most commonly used products are Tein, Eibach, H&R & B&G springs. While there are other springs that may fall into this category and are worthy of research, these seem to be the most popular and are all considered by most users to be appealing, inexpensive, and fairly strut friendly when used with the OEM struts.

Progressive Springs is what you go for when you upgrade your springs. In actual fact, it's difficult not to get progressive springs when you upgrade - most of the aftermarket manufacturers make them like this.

 


Increasing the number of coils decreases the stiffness of the spring. Thus, a progressive spring is progressive because the two parts are compressed equally until the tightly wound part locks up, effectively shortening the spring and reducing its compliance. So for normal driving, you'll be using mostly the upper 3 or 4 'tight' winds to soak up the average bumps and potholes. When you get into harder driving, like cornering at speed for example, because the springs are being compressed more, they resist more. The effect is to reduce the suspension travel at the top end resulting in less body roll, and better road-holding.

Invariably, the fact that the springs are progressively wound is what accounts for the lowering factor. The springs aren't made shorter - they're just wound differently. Of course the material that aftermarket springs are made of is usually a higher grade than factory spec simply because it's going to be expected to handle more loads.


Coilovers:

 

Coilovers are the “best” suspension mod in that the struts are designed to work with the springs. You get the coilovers if you want to be able set up your car's height and ride firmness all in one package. Coilovers also allow you to fine-tune your car/ssuspension parameters for racing as well as daily driving.

Another feature that coilovers allow you to do is corner weighting, also known as corner balancing. In short, corner weighting evens out your car’s suspension during turns so that your vehicle reacts identically in both left and right turns.

While you can use coilovers as an appearance mod, springs are a more cost effective option.

High-end kit have controls on the shock absorber for both compression and rebound damping. Typically the rebound damping will be a screwdriver slot at the top of the shock absorber, and compression damping will be a knob either on the side or on the remote reservoir. Ultra-high-end kit has separate controls for high- and low-speed damping. ie. you can make the shock absorber behave differently over small bumps (low speed compression and rebound) than it does over large bumps (high speed compression and rebound).

You'll need to understand how shocks work first. Compression (also called bump) is to control how fast or slow you want the shock to compress when you hit a bump or apex at the track. Soft compression will allow the shocks to compress faster and hard compression will have make the shocks compress slower. Softer compression setting will make the car feel comfortable at low speeds, but if it's set to too soft, the shocks will compress too fast when you go over a bump. If it's set too hard, the shocks will compress too slow when you drive over imperfections or apex at the track. It means the shocks will not absorb and transfer the energy fast enough and make the tires lose contact.

Rebound, on the other hand, is the opposite. It allows the shocks to return back to the initial compressed stage after you drive over a bump. Softer rebound will allow the shocks to return to it's original state faster and harder rebound will do the opposite. Generally speaking, soft rebound will give you a much comfortable ride under low speed condition, however, you'll feel floaty under high speed condition. Harder rebound setting will give you more stability, however, if it's set too hard, the shocks will be slower to return the initial state after it was compressed, causing traction loss.

I hope I haven't confused you yet. As you can see, it's a delicate balance between compression and rebound adjustments. Of course, the spring rates play a role also. Since we're not replacing the springs, I won't go there.

Now on the KW V3, the compression (bump) is adjusted from the bottom of the shock assembly. If you look from underneath the car, clockwise turn is higher and counter clockwise is lower bump. The adjustment range is 0.25 turn for every sweep you make either way.

Rebound setting is done from the top of the shock assembly. It's determined by clicks. Clockwise is harder rebound and counter clockwise will be softer. KW recommends 6 clicks in the front and 9 in the rear.

If you want the most out of the shocks, you need to make sure you're within KW recommended range in terms of ride height. Suspension tuning seems pretty simple, but if you want a neutral handling car, it's quite the contrary.

On my set up, I have the compression set at KW recommended setting, which is 0.5 turns from full stiff in the front and 0.75 turns for the rear. As for rebound, I am at 5 clicks from the stiffest in the front and 7 clicks in the rear. The reason I went a tiny bit harder rebound in the rear is to reduce the understeer. It's all your personal preference.

Sources:
Suspension bible
Unabomber @ NASIOC Forums