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Tech Center
Suspension IV: Improving Your Suspension
By Scott Memmer
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The long, bumpy ride of
our suspension series is drawing to a close.
In this, our final installment,
we'll discuss some ways you can improve your car's handling ability through
suspension modification. Then we'll close by taking a look back at where we've
been, review some basic suspension principles, and set you free to go cruising
down the road.
By now you should have a working understanding of automotive suspension systems.
Clearly, engineers have a myriad of choices to make when designing a car's suspension.
Just as clearly, those choices affect the quality and character of the car's
ride. But there's one last area we haven't discussed: aftermarket modification.
First, a proviso. The average driver who commutes back and forth to the office
every day may need to do nothing more than replace existing components to improve
performance.
Think about it: two hundred-plus round trips to the office every year, multiplied
by, say, five or ten years of commuting -- things begin to wear and tear. Swapping
out the existing components for OEM replacements can have a hugely positive
effect on the car's handling ability. Shocks, springs, bushings -- all these
wear with time. If you're an average motorist with an average car who drives
an average commute every day, consider replacing the worn components and going
no further. This will save you time and money, and enhance your driving experience.
There are, however, those drivers who want or need better performance. Consider
a soccer mom who pulls a trailer on the weekends. Or that young buck with an
Acura who likes to challenge his buddies through the canyons.
What can you do to improve your car's suspension? What alterations can you make
in your car's springs and shocks that will enhance its handling capabilities?
Another proviso: proceed with caution. As our Managing Editor likes to say,
"It's much easier to screw up your suspension than make it better." Remember,
well-trained engineers sometimes spend years tuning a car's suspension, balancing
spring rate against shock stiffness. You can mess it up with one quick mod.
That being said, there are things you can do to improve your car's handling.
Those same engineers often make design decisions based largely on cost. If your
focus is less on the bottom line and more on the right-front strut that keeps
bottoming out every time you hit a hard left turn, you can definitely make changes
that will improve your ride.
Automotive engineers design passenger vehicles to appeal to a wide spectrum
of drivers and perform competently under a variety of conditions. The suspension
systems in the Honda Accord, Ford Taurus and Toyota Camry, for instance -- like
the other components in those cars -- are intentionally designed to be as inoffensive
as possible. They aim for the middle ground.
The manufacturers of these cars want to attract as many buyers as they can,
to vie for the sales crown of "most popular passenger vehicle." Not best,
mind you, just most popular. And, like that cheerleader back in high school
whom everyone voted Most Popular until they really got to know her, at which
point they couldn't stand her (she now lives in a one-room apartment
with her three bratty children, one from each failed marriage), familiarity
can sometimes breed contempt.
Taurus, Accord and Camry are designed to work moderately well across a broad
range of performance parameters, something which may or may not match your individual
requirements. This sort of democratic design-by-committee works well for the
masses, but not for drivers with specific needs.
(Please don't write us defending Camry, Taurus and Accord. We like these cars
-- a lot, actually. We just use them to illustrate the performance tradeoffs
auto manufacturers make when designing a bestseller.)
The point being, you may
have specific needs. You may want to fly where others plod. A finely tuned suspension
system can help you get there.
Let's a take a look at each component in the system and what you can do to improve
its performance.
Springs
You may recall that in Part One we discussed spring rate. This is the amount
of "give" or "stiffness" a spring has, measured in pounds per inch. As already
mentioned, design engineers work across a broad spectrum of performance conditions.
They paint on a large canvas.
But let's say someone is going to be pulling a fifth-wheel trailer. They have
a Ford F250 pickup that "dips" too much in the back when the fifth-wheel is
in its cradle. This may indicate the need for a stiffer suspension system.
Usually a buyer will know ahead of time about their towing needs and order the
vehicle from the factory with a trailer-towing package. But let's assume this
consumer came to the camping lifestyle late in life and now wants to retrofit
their F250 for the task. What should he or she do?
First, beef up the rear springs. Replace the existing leaf springs with a set
that offers a higher spring rate. This will create more resistance or "lift"
on the back end, working against the weight of the fifth-wheel trailer. The
new springs, because of their increased strength, will level off the vehicle
and cause it to stand more upright on the road. In other words, the weight of
the vehicle and the trailer will be more evenly distributed across all four
wheels, making the truck handle and steer better (remember, as the tail end
sinks the front will tend to rise, causing reduced steering control).
A word of caution here: UNLESS YOU HAVE THE NECESSARY TOOLS, DO NOT ATTEMPT
TO CHANGE SPRINGS ON YOUR OWN.
Replacing springs requires a tool called a spring compressor. If you don't have
one, don't do this procedure. Leave the job to the professionals. Springs --
particularly coil springs -- operate under thousands of pounds of pressure and
tension. People have been seriously injured, even killed, trying to replace
their own springs.
While you're talking to your mechanic, have him advise you on which springs
to install. You don't necessarily want the stiffest springs available. If towing
the fifth-wheel is a small part of what you'll be using the vehicle for -- and
for most people it is -- then consider a medium-rate spring, something stiffer
than the current springs on the vehicle, but not overly stiff. Avoid going too
far the other way. Otherwise, you'll end up with a vehicle that rides like a
brick sh__ -- well, you know what we mean.
Some well-known aftermarket spring manufacturers include Eibach, Belltech, H&R,
InTrax, Speedtech and Tokico.
Shocks
Let's go back to that Ford F250. Our camping aficionado has replaced the rear
leaf springs with a stiffer set, and they work fine, but the truck dives excessively
and recovers slowly when going over potholes or through dips. Our camper needs
stiffer shocks.
Unlike springs, shock absorbers present a myriad of choices to the consumer.
As you saw in Part Two of this series, there are almost as many shocks as there
are cars. But in the case of our Ford F250, we can narrow our choices.
First, our camper can consider replacing the existing shocks with OEM replacements.
If they are more they five years old, they have almost certainly lost peak performance.
Or he could install gas shocks, which will be stiffer still. However, in this
instance, we would suggest a more aggressive approach.
Air shocks afford the opportunity to adjust the stiffness of the ride on an
"as needed" basis. When the fifth-wheel is on, pump 'em up. When it's not, deflate
'em.
Better still, an automatic level control system will do the job for you -- as
the name implies -- automatically. When engaged, the system, which includes
four air shock absorbers, an air compressor and various sensors and switches,
monitors and adjusts the height of the vehicle continuously. When the load is
heavy, on goes the pump and up go the shocks; when light, the system automatically
lowers. This is an excellent solution for vehicles that commute during the week
and tow on the weekends.
Some of the better known shock-absorber suppliers include Bilstein, Koni, KYB
and Tokico.
Stabilizer
Bars
Also known as anti-roll or sway bars, these components work by distributing
the weight of a cornering vehicle to the opposite side of the car.
Adding a stabilizer bar to a vehicle that does not already have one can greatly
reduce yawing and swaying.
Similar to a torsion bar in operation (see Part Two for more on torsion bars),
a stabilizer bar runs from one side of the vehicle to the other, attaching to
the frame and control arms via a simple bushing arrangement. When the car goes
through a turn, the bar begins to twist, but resists motion. This resistance
distributes vehicle weight more evenly from side to side, lending the vehicle
more stability.
Stabilizer bars can be added front or rear. Such vendors as Suspension Technology
and Eibach manufacture stabilizer bar kits for the aftermarket.
Strut Tower Brace
A strut tower brace is a simple metal bar that stretches across the front MacPherson
strut towers, unitizing the front end by increasing rigidity.
NOTE: Make sure your car is on the ground, removed from jackstands, before performing
the procedure below.
Open the hood of your car.
Locate where the front struts attach to the body of the car -- you'll see a
bolt punching through the top of each wheelwell with a nut tightened down on
it. The strut tower brace goes between these two bolts. Simply remove the nut
and washer, slide the strut brace over the bolt, and anchor it down with the
washer and nut. Easy as pie.
A lot of aftermarket suppliers build strut tower braces. Be sure to order the
correct one for your car and body type. It's amazing what such a simple modification
can do to increase front-end rigidity. You'll notice the difference right away.
And it's cheap. Most strut tower braces cost around a hundred dollars.
Aftermarket manufacturers of these components include GReddy, Neuspeed, Suspension
Technology and Eibach.
In Closing...
Well, as the Grateful Dead once said, what a long strange trip it's been. This
brings to a close our Four-Part series on suspension.
If you have any specific questions regarding suspension problems or issues,
address them to techcenter@edmunds.com
and we'll try to get back to you as soon as possible with an answer.
Remember, although a finely tuned suspension system is not essential to the
operation of a motor vehicle, it will add to your driving pleasure and comfort
for years to come. It also acts as a buffer between the highway and the rest
of the components in the car, protecting them, as well as you, from the undue
stresses and strains of the road.
For your convenience, we've pasted the URLs to the three previous articles in
the series below.
Shake, Rattle and
Roll: Suspension Basics
Suspension II: Still
Rocking After All These Years
Suspension III:
Active Suspension Systems
Stay out of the potholes, and keep your eyes on the road.
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