Post by Sabertooth on Dec 4, 2018 10:01:17 GMT -5
Alright, so you've got some power (or maybe you don't) and you want some handling to go with it. You look out there, and you see lowering springs, and coilover kits available, but don't know what it means.
Lowering springs are, as the name implies, springs that lower your car. They go on OEM style struts (which they don't come with) and are, at least up front, a cheap way to lower your car, and add some performance potentially. You'll find quality lowering springs in the $200-$300 area typically
With them, you'll find higher springrates and they'll give you an amount that they drop the car. Typically the spring rate is about 2x. The downside here is you're on an OEM strut that isn't made for being run so compressed, and they tend to wear out quickly. That, combined with the wear already on the used struts you'd typically be putting them on makes for poor rebound and damping, and can have a rocky feel, or even bouncy.
The other, more expensive option up front is to buy adjustable coilovers. These tend to cost about $1000. The advantage to these is that they often come with height adjustment and damping adjustment, as well as camber plates in some cases. They're also purpose built to handle the shock of the abuse they'll see in track use when you get a high quality set, and have less cavitation inside (gas bubbles from the shock of being compressed) which keeps them acting predictably and at full strength. You'll find they tend to come with a springrate about 4x that of OEM, but you can have custom spring rates depending on the company and item.
What a higher springrate does is it makes it harder to compress the strut assembly, and it will attempt to rebound harder. That will make for low roll in corners, less dive when braking, and keeps the nose down more during hard acceleration, which is important on a FWD car especially. In figuring out what spring rate you want/need, you need to consider the environment you'll be driving in, your goals, tire setup, and weight balance. A good starting point is to have all 4 corners of the car at equal height. To do this, you'd need to find the relationship of the weight at each wheel and compare them. Eg, at a 60:40 weight balance, the front spring rate may be 6k, rear be 4k. Then, to adjust handling characteristics you go from there. Making the rear stiffer will reduce understeer, but could cause oversteer or an unpredictable ride. Fast laps are only good when you can do it reliably!! Typically OEM setups favour understeer, as do many endurance racing cars. It gives a better driver experience.
Dampening is how much force the struts take away, in a sense. It prevents the springs from bouncing your car around at the harmonic rate of the springs. How it works is that inside the strut you have a setup which is a piston moving in a cylinder with valves on it. The size of those valves determines how fast oil can flow between the inner and outer cylinders. That flow of oil cushions, and controls the speed of compression and extension of the struts. When set too stiff, you'll have a very rough ride with your wheels being unable to conform to the road surface. When set too low, you'll have a very bouncy ride. Offroad can get away with having much lower dampening, although the spring rate and suspension travel distances must also be tuned for that. Most important on the road is to have something that is a safe setup. You don't want a pothole to send you to the emergency room. For a track car, play around with it until you find what works for you.
Camber is the angle of your wheels when viewed from the front. It is there to counter body roll in a corner and give your outer wheels in the corner more grip, allowing for faster cornering speeds. The amount of camber you run has to be determined from how hard you're cornering, how much body roll you have, body twist, and the tires used. When using a sticky tire, you can add more camber. On a street tire setup, stay OEM, about -0.5°. On slicks, you'll have to play around but may even go as high as -2° and see use, or higher if you have a lot of roll. Positive camber is never good. The downside to camber is straight line performance is reduced, and you get more wear inside the tires than on the outside, ruining the set prematurely.
Ride height adjustment is an easier one. Lower ride height, lower center of gravity. Raise the rear compared to the front, add oversteer. Too low, and you'll scrape. Scraping is never good, and can cause loss of control. Too high you're giving up some center of gravity lowering to be gained.
Ok, now for Anti roll bars. These are torsion bars connecting the left and right side suspension to share the load, and prevent body roll. Typically you want the front to be stiff, and rear to be softer unless you have a reason not to. Again, the ratio should have you starting by looking at the front:back weights, then adjusting from there. There is a balance. Stiffer reduces roll, and as such you can run less camber for a flatter setup, which is more predictable and you reduce the cons of high camber (straight line traction, low speed cornering traction (street driving)). Too stiff, and the car will want to slide instead of just understeers/oversteering. A 4 wheel slide is not what you ever want happening, and once it starts you may as well be on ice.
How stiff do you want? Well, that again comes down to your setup everywhere else. If you're just picking things up off the shelf anyway, you probably don't need to worry about that. If you're a competitive racer, you're probably already aware of this all.
So to recap:
Spring rate, how stiff the springs are
Lowering, how much the car is lowered by
Dampening, how much force the struts absorb
Camber, wheel angle from front
Anti roll bars, bars for preventing body roll
Everything in suspension is a balance, and all parts work together. This is a simplified guide that ignores things like control arm length, wheel offset, strut placement, caster angle, etc. Suspension tuning is best done on a track. Take it easy on the new setup, and dial it on from there. I hope this guide helps someone out there. Be fast, but also be safe.
Lowering springs are, as the name implies, springs that lower your car. They go on OEM style struts (which they don't come with) and are, at least up front, a cheap way to lower your car, and add some performance potentially. You'll find quality lowering springs in the $200-$300 area typically
With them, you'll find higher springrates and they'll give you an amount that they drop the car. Typically the spring rate is about 2x. The downside here is you're on an OEM strut that isn't made for being run so compressed, and they tend to wear out quickly. That, combined with the wear already on the used struts you'd typically be putting them on makes for poor rebound and damping, and can have a rocky feel, or even bouncy.
The other, more expensive option up front is to buy adjustable coilovers. These tend to cost about $1000. The advantage to these is that they often come with height adjustment and damping adjustment, as well as camber plates in some cases. They're also purpose built to handle the shock of the abuse they'll see in track use when you get a high quality set, and have less cavitation inside (gas bubbles from the shock of being compressed) which keeps them acting predictably and at full strength. You'll find they tend to come with a springrate about 4x that of OEM, but you can have custom spring rates depending on the company and item.
What a higher springrate does is it makes it harder to compress the strut assembly, and it will attempt to rebound harder. That will make for low roll in corners, less dive when braking, and keeps the nose down more during hard acceleration, which is important on a FWD car especially. In figuring out what spring rate you want/need, you need to consider the environment you'll be driving in, your goals, tire setup, and weight balance. A good starting point is to have all 4 corners of the car at equal height. To do this, you'd need to find the relationship of the weight at each wheel and compare them. Eg, at a 60:40 weight balance, the front spring rate may be 6k, rear be 4k. Then, to adjust handling characteristics you go from there. Making the rear stiffer will reduce understeer, but could cause oversteer or an unpredictable ride. Fast laps are only good when you can do it reliably!! Typically OEM setups favour understeer, as do many endurance racing cars. It gives a better driver experience.
Dampening is how much force the struts take away, in a sense. It prevents the springs from bouncing your car around at the harmonic rate of the springs. How it works is that inside the strut you have a setup which is a piston moving in a cylinder with valves on it. The size of those valves determines how fast oil can flow between the inner and outer cylinders. That flow of oil cushions, and controls the speed of compression and extension of the struts. When set too stiff, you'll have a very rough ride with your wheels being unable to conform to the road surface. When set too low, you'll have a very bouncy ride. Offroad can get away with having much lower dampening, although the spring rate and suspension travel distances must also be tuned for that. Most important on the road is to have something that is a safe setup. You don't want a pothole to send you to the emergency room. For a track car, play around with it until you find what works for you.
Camber is the angle of your wheels when viewed from the front. It is there to counter body roll in a corner and give your outer wheels in the corner more grip, allowing for faster cornering speeds. The amount of camber you run has to be determined from how hard you're cornering, how much body roll you have, body twist, and the tires used. When using a sticky tire, you can add more camber. On a street tire setup, stay OEM, about -0.5°. On slicks, you'll have to play around but may even go as high as -2° and see use, or higher if you have a lot of roll. Positive camber is never good. The downside to camber is straight line performance is reduced, and you get more wear inside the tires than on the outside, ruining the set prematurely.
Ride height adjustment is an easier one. Lower ride height, lower center of gravity. Raise the rear compared to the front, add oversteer. Too low, and you'll scrape. Scraping is never good, and can cause loss of control. Too high you're giving up some center of gravity lowering to be gained.
Ok, now for Anti roll bars. These are torsion bars connecting the left and right side suspension to share the load, and prevent body roll. Typically you want the front to be stiff, and rear to be softer unless you have a reason not to. Again, the ratio should have you starting by looking at the front:back weights, then adjusting from there. There is a balance. Stiffer reduces roll, and as such you can run less camber for a flatter setup, which is more predictable and you reduce the cons of high camber (straight line traction, low speed cornering traction (street driving)). Too stiff, and the car will want to slide instead of just understeers/oversteering. A 4 wheel slide is not what you ever want happening, and once it starts you may as well be on ice.
How stiff do you want? Well, that again comes down to your setup everywhere else. If you're just picking things up off the shelf anyway, you probably don't need to worry about that. If you're a competitive racer, you're probably already aware of this all.
So to recap:
Spring rate, how stiff the springs are
Lowering, how much the car is lowered by
Dampening, how much force the struts absorb
Camber, wheel angle from front
Anti roll bars, bars for preventing body roll
Everything in suspension is a balance, and all parts work together. This is a simplified guide that ignores things like control arm length, wheel offset, strut placement, caster angle, etc. Suspension tuning is best done on a track. Take it easy on the new setup, and dial it on from there. I hope this guide helps someone out there. Be fast, but also be safe.
