72Chero
03-07-2008, 01:52 PM
A vehicle that handles well is considerably more fun to drive than a vehicle that doesn’t handle well. This does not mean that your car has to corner like an Corvette and come with a stiff, harsh ride; it is entirely possible to improve your cornering ability while retaining a comfortable ride. The secret is in finding the right mix of components- shocks, springs, and sway bars that will give you the results you’re looking for. The problem is that few people really understand how these parts work, but hopefully after reading this article you’ll have the knowledge you need to setup your car to handle like a dream. This was written with street cars in mind, and there are a lot more technical details about all of these components that could be applied in race applications. Be sure to discuss these topics in the Smog Era Forums.
Shocks
Probably the easiest suspension component to understand, shocks are usually the most familiar piece of equipment when it comes to this area of your vehicle. The ride quality of your car is most often attributed to your shock absorbers. Shocks control the up and down movement of your suspension and help keep your tires planted to the road. Without them, your car would just bounce all over the road and driving would be nearly impossible.
Shocks function by forcing hydraulic fluid though one or more valves as the piston inside the shock moves up and down. The valves, which limit the amount of fluid that can pass through, control how quickly the piston can move. Some shocks have separate valves for up and down movements, which provides a different rate for each direction. In general, a firmer shock will make your vehicle feel “tighter” and handle better because the suspension will resist movement. The downside to this is that it will also make the ride noticeably rougher when on anything but smooth asphalt. If this is acceptable to you, then you would want to use a set of good quality nitrogen-charged shocks. Nitrogen-filled shocks are superior to standard gas-filled shocks in that the pressurized nitrogen prevents bubbles from forming in the hydraulic liquid. This effect, called foaming, is caused by heat built up by rapid movements of the shock absorber and reduces the resistance the fluid normally provides.
Another shock absorber design that has become popular in recent years is the “variable valve” design. These use a motion-sensing valve that can switch the shock from firm to soft depending on the surface you drive over. Normally they act as a standard, firm shock, but if there is sudden and rapid up-and-down movement, the valve opens to allow more fluid to flow through. These shocks are best suited for people who want to tighten up their suspension a bit, but do not want much compromise when it comes to ride quality. Another thing to consider with these shocks is the firmness of your springs. The higher the rate of your springs, the less effect you will notice from this type of shock absorber. Therefore, if you are running stiff springs, obviously trying to get the tightest handling possible, go with firm set of conventional nitrogen-charged shocks. If want to maintain a comfortable ride but improve your cornering ability, the variable valve design could be just what you’re looking for.
Springs
Springs have the most direct control over the handling of your vehicle. This is where the entire weight of your car rests, and when you go around a turn they must absorb the force of that weight being shifted to one side. Since all of this is about supporting a certain amount of weight, spring stiffness, called the “spring rate,” is measured by the number of pounds is takes to compress the spring one inch. For example, if you have a spring rated at 500 pounds, it will take 500 pounds to compress it one inch, and it would take 1,000 pounds to compress it two inches. If you are trying to get the tightest handling possible with your vehicle, you generally want to use as high of a spring rate as you are comfortable with so when you go around a corner and the weight shifts to the outside, your springs will be able to support it without allowing the vehicle to tip, sway, and loose control.
For many vehicles, it is simply impossible to find aftermarket springs designed for them. No problem! This is a mistake people commonly make when they decide to upgrade their suspension- if they can’t find springs, they don’t bother with them. The truth is, you can probably find high-rate, heavy-duty springs for your vehicle right at your local auto parts store. Auto manufacturers created multiple front spring rates for their vehicles since a single platform might have to support everything from a lightweight 6-cylinder engine all the way up to a big-block. For rear springs, there are different rates for 2-doors, 4-doors, trailer towing packages, and so on. There were even many vehicles that you can get “police package” springs for, which are usually the highest rate springs available. So if your car is a 2-door coupe with a small-block V8, you could see a real improvement in your handling by switching to springs meant for a 4-door, big-block car.
Once you find a set of springs, you still might have some work to do before actually installing them. Sometimes, the heavy-duty springs, in addition to being a higher rate, are taller than your original springs. You might want your vehicle to be lower than stock. You might want to increase the spring rate even more. Luckily, there is a way to accomplish all of this relatively easily. You may have heard of the practice known as “cutting” springs. This is a method applied to coil springs that will increase their capacity and can also be used to lower your vehicle.
You see, there are three things that determine the rate of a spring: thickness of the wire, diameter of the coils, and the number of coils. You cannot change the first two characteristics, but you can change the number of active coils. Active coils are the coils in the spring that do not come in contact with anything, as opposed to “dead” coils, which are the two end coils that come in contact with the mounting locations. In general, the fewer number of active coils a spring has, the higher the spring rate will be. Therefore, by cutting off a predetermined amount of coil, you will make the spring shorter and also increase it’s rate. There are a couple simple math equations you can use to calculate the amount of coil to remove and to determine what your new spring rate will be:
For example, we will start with a 500 pound spring with 8 active coils. If you want to end up with a spring rate of 550 pounds, you first multiply the spring rate by the number of active coils:
(500) * (8) = 4000
Next, divide this number by the spring rate that you want:
(4000) / (550) = 7.273
This is the number of active coils that will produce your desired spring rate. Just find the difference between this number and the original number of coils to determine the amount to cut off. In this case, it would be .73, or about three-fourths of a coil. Don’t be afraid to round off your figures and estimate the numbers. In reality this spring might have 8.153 coils but considering that to be 8 won’t make a noticeable difference. You just want to make sure that you modify both springs of a pair equally.
It’s a little tougher to determine how high, or low, your vehicle will sit with your newly cut springs, but comparing the height of your first cut spring to its matching original will give you a good idea. Also remember to use good judgment when modifying your springs- you can’t put them back together after you cut them, and if you don’t like the results you’ve wasted an expensive pair of springs. Another thing to remember is that the information discussed here applies to standard coil springs only. Progressive rate springs operate on slightly different principles, and I shouldn’t have to tell you that leaf springs function totally different.
Sway bars
People generally realize that a sway bar on a vehicle improves the handling, but few people could tell you how, why, or what it does. They usually just shop around for the biggest sway bar they can find, bolt it on their car, and go about their business. There’s nothing wrong with that, and it usually does achieve the desired result, but we feel that by having an understanding of how this component functions will give you much more control over the ride and handling characteristics of your vehicle.
Without a sway bar, when a vehicle goes around a turn the weight of the chassis is shifted to the outside. This puts all of the weight on the springs of that side, compressing them, and makes the whole vehicle lean to the outside. At this point, the majority of the weight is applied to only the two outside tires. Obviously this is not desirable if our goal is to get around the turn as quickly and with as much control as possible.
Adding a sway bar to a vehicle couples the suspension on both sides to each other and to a pivot point on the chassis. Having the suspension coupled together means that when one side is compressed, it will also compress the springs on the other side. This effectively increases the spring rate on the side being compressed. A sway bar is like a spring itself, in that it has some twist to it. For example, we have 500 pound springs, coupled by a sway bar. One side is compressed which puts force on the sway bar which in turn puts force on the other spring. The sway bar will twist to some degree, and may only transfer 50% of the energy between the springs. This will cause the 500 pound spring on the outside to act like a 750 pound spring (50% of the other spring rate is added to it’s own 500 pounds) and in turn keep the car more level. In general, the larger the diameter of the sway bar, the more energy it will share between the springs. This is why a 1.5-inch sway bar is more effective than a .75-inch sway bar.
The sway bar only comes into effect when the sides of the suspension are compressed unevenly. If you are driving through a parking lot in your sway bar-equipped vehicle and drive over a speed bump, your springs compress at the same time and act like their standard 500 pound selves since the sway bar is not twisted. If you drive over a speed bump with only one side of your car, the sway bar goes into effect and your spring may feel like a 750 pound spring for the same reason we stated before.
Putting it all Together
If you’re looking for all-out cornering ability, using the firmest shocks, stiffest springs, and biggest sway bars will probably do the job. On the other hand, if you want to keep a comfortable ride but reduce body roll in turns you may find that a set of variable rate shocks, standard springs, and large-diameter sway bars will work well. When it comes to handling, the trick is to find the setup that will distribute the vehicle’s weight correctly among all the tires for any given situation. Now that you have a general understanding of how the different components of your suspension function, you should be able to put together a system that will meet your own ride and handling needs.
Shocks
Probably the easiest suspension component to understand, shocks are usually the most familiar piece of equipment when it comes to this area of your vehicle. The ride quality of your car is most often attributed to your shock absorbers. Shocks control the up and down movement of your suspension and help keep your tires planted to the road. Without them, your car would just bounce all over the road and driving would be nearly impossible.
Shocks function by forcing hydraulic fluid though one or more valves as the piston inside the shock moves up and down. The valves, which limit the amount of fluid that can pass through, control how quickly the piston can move. Some shocks have separate valves for up and down movements, which provides a different rate for each direction. In general, a firmer shock will make your vehicle feel “tighter” and handle better because the suspension will resist movement. The downside to this is that it will also make the ride noticeably rougher when on anything but smooth asphalt. If this is acceptable to you, then you would want to use a set of good quality nitrogen-charged shocks. Nitrogen-filled shocks are superior to standard gas-filled shocks in that the pressurized nitrogen prevents bubbles from forming in the hydraulic liquid. This effect, called foaming, is caused by heat built up by rapid movements of the shock absorber and reduces the resistance the fluid normally provides.
Another shock absorber design that has become popular in recent years is the “variable valve” design. These use a motion-sensing valve that can switch the shock from firm to soft depending on the surface you drive over. Normally they act as a standard, firm shock, but if there is sudden and rapid up-and-down movement, the valve opens to allow more fluid to flow through. These shocks are best suited for people who want to tighten up their suspension a bit, but do not want much compromise when it comes to ride quality. Another thing to consider with these shocks is the firmness of your springs. The higher the rate of your springs, the less effect you will notice from this type of shock absorber. Therefore, if you are running stiff springs, obviously trying to get the tightest handling possible, go with firm set of conventional nitrogen-charged shocks. If want to maintain a comfortable ride but improve your cornering ability, the variable valve design could be just what you’re looking for.
Springs
Springs have the most direct control over the handling of your vehicle. This is where the entire weight of your car rests, and when you go around a turn they must absorb the force of that weight being shifted to one side. Since all of this is about supporting a certain amount of weight, spring stiffness, called the “spring rate,” is measured by the number of pounds is takes to compress the spring one inch. For example, if you have a spring rated at 500 pounds, it will take 500 pounds to compress it one inch, and it would take 1,000 pounds to compress it two inches. If you are trying to get the tightest handling possible with your vehicle, you generally want to use as high of a spring rate as you are comfortable with so when you go around a corner and the weight shifts to the outside, your springs will be able to support it without allowing the vehicle to tip, sway, and loose control.
For many vehicles, it is simply impossible to find aftermarket springs designed for them. No problem! This is a mistake people commonly make when they decide to upgrade their suspension- if they can’t find springs, they don’t bother with them. The truth is, you can probably find high-rate, heavy-duty springs for your vehicle right at your local auto parts store. Auto manufacturers created multiple front spring rates for their vehicles since a single platform might have to support everything from a lightweight 6-cylinder engine all the way up to a big-block. For rear springs, there are different rates for 2-doors, 4-doors, trailer towing packages, and so on. There were even many vehicles that you can get “police package” springs for, which are usually the highest rate springs available. So if your car is a 2-door coupe with a small-block V8, you could see a real improvement in your handling by switching to springs meant for a 4-door, big-block car.
Once you find a set of springs, you still might have some work to do before actually installing them. Sometimes, the heavy-duty springs, in addition to being a higher rate, are taller than your original springs. You might want your vehicle to be lower than stock. You might want to increase the spring rate even more. Luckily, there is a way to accomplish all of this relatively easily. You may have heard of the practice known as “cutting” springs. This is a method applied to coil springs that will increase their capacity and can also be used to lower your vehicle.
You see, there are three things that determine the rate of a spring: thickness of the wire, diameter of the coils, and the number of coils. You cannot change the first two characteristics, but you can change the number of active coils. Active coils are the coils in the spring that do not come in contact with anything, as opposed to “dead” coils, which are the two end coils that come in contact with the mounting locations. In general, the fewer number of active coils a spring has, the higher the spring rate will be. Therefore, by cutting off a predetermined amount of coil, you will make the spring shorter and also increase it’s rate. There are a couple simple math equations you can use to calculate the amount of coil to remove and to determine what your new spring rate will be:
For example, we will start with a 500 pound spring with 8 active coils. If you want to end up with a spring rate of 550 pounds, you first multiply the spring rate by the number of active coils:
(500) * (8) = 4000
Next, divide this number by the spring rate that you want:
(4000) / (550) = 7.273
This is the number of active coils that will produce your desired spring rate. Just find the difference between this number and the original number of coils to determine the amount to cut off. In this case, it would be .73, or about three-fourths of a coil. Don’t be afraid to round off your figures and estimate the numbers. In reality this spring might have 8.153 coils but considering that to be 8 won’t make a noticeable difference. You just want to make sure that you modify both springs of a pair equally.
It’s a little tougher to determine how high, or low, your vehicle will sit with your newly cut springs, but comparing the height of your first cut spring to its matching original will give you a good idea. Also remember to use good judgment when modifying your springs- you can’t put them back together after you cut them, and if you don’t like the results you’ve wasted an expensive pair of springs. Another thing to remember is that the information discussed here applies to standard coil springs only. Progressive rate springs operate on slightly different principles, and I shouldn’t have to tell you that leaf springs function totally different.
Sway bars
People generally realize that a sway bar on a vehicle improves the handling, but few people could tell you how, why, or what it does. They usually just shop around for the biggest sway bar they can find, bolt it on their car, and go about their business. There’s nothing wrong with that, and it usually does achieve the desired result, but we feel that by having an understanding of how this component functions will give you much more control over the ride and handling characteristics of your vehicle.
Without a sway bar, when a vehicle goes around a turn the weight of the chassis is shifted to the outside. This puts all of the weight on the springs of that side, compressing them, and makes the whole vehicle lean to the outside. At this point, the majority of the weight is applied to only the two outside tires. Obviously this is not desirable if our goal is to get around the turn as quickly and with as much control as possible.
Adding a sway bar to a vehicle couples the suspension on both sides to each other and to a pivot point on the chassis. Having the suspension coupled together means that when one side is compressed, it will also compress the springs on the other side. This effectively increases the spring rate on the side being compressed. A sway bar is like a spring itself, in that it has some twist to it. For example, we have 500 pound springs, coupled by a sway bar. One side is compressed which puts force on the sway bar which in turn puts force on the other spring. The sway bar will twist to some degree, and may only transfer 50% of the energy between the springs. This will cause the 500 pound spring on the outside to act like a 750 pound spring (50% of the other spring rate is added to it’s own 500 pounds) and in turn keep the car more level. In general, the larger the diameter of the sway bar, the more energy it will share between the springs. This is why a 1.5-inch sway bar is more effective than a .75-inch sway bar.
The sway bar only comes into effect when the sides of the suspension are compressed unevenly. If you are driving through a parking lot in your sway bar-equipped vehicle and drive over a speed bump, your springs compress at the same time and act like their standard 500 pound selves since the sway bar is not twisted. If you drive over a speed bump with only one side of your car, the sway bar goes into effect and your spring may feel like a 750 pound spring for the same reason we stated before.
Putting it all Together
If you’re looking for all-out cornering ability, using the firmest shocks, stiffest springs, and biggest sway bars will probably do the job. On the other hand, if you want to keep a comfortable ride but reduce body roll in turns you may find that a set of variable rate shocks, standard springs, and large-diameter sway bars will work well. When it comes to handling, the trick is to find the setup that will distribute the vehicle’s weight correctly among all the tires for any given situation. Now that you have a general understanding of how the different components of your suspension function, you should be able to put together a system that will meet your own ride and handling needs.