Springs
Stiffer, Stronger, Lower...Faster!
One of the first things enthusiasts
do to increase the road manners of their ride is to
install more aggressive springs.
Shorter, more aggressive springs
achieve two goals: 1st - shorter springs decrease body
roll and lower the cars center of gravity. The second
benefit is that higher spring rates reduce suspension
movement, with the hope of improving the wheel's contact
patch with the road.
The downside is the eternal compromise:
improved handling typically means a harsher ride. What
is harsh to one person may not be harsh to the next.
Though I used to think a "go-kart" suspension
was the ultimate set-up, I find the older I get the
less "harshness" I can take on my daily commute.
Progressive Springs
To help with the harshness issue, many spring manufacturers have "progressive" springs. What it really means is that the spring rate changes the more the spring is compressed. For example, a spring can be 10% softer than stock in its first inch of compression and then increase to 35% stiffer than stock as it is compressed farther. For daily driving, progressive springs will be more comfortable on the freeway and the provide the extra performace you want when cornering hard.
When installing new springs, be sure that the dampners
(shocks) are correctly matched to the springs. Some spring manufactures design their springs to work with the factory dampers, while more aggressive spring rates require new dampers.
Also, when you lower the car, you automatically change
the camber of your suspension (your wheels are tilted
in). Though increased camber usually helps with grip
at cornering limits, too much camber is a bad thing...just
ask my wife when I wore out my Bridgestone S0-2's ($225
each) in about 3 months (asking to spend another $1,000
on tires that have no inner tread is not a wise thing).
Therefore, be sure to get an alignment after installing
new springs.
Since the WRX is meant to be driven off road, be careful
not to reduce the suspension travel too much (unless,
you never plan to "rally"...but to me, that
is what makes the WRX different than every other car
on the road...it was MEANT to be driven off road...and
boy is it a blast!)
Linear Springs
A linear spring rate has one rate throughout its deflection. Meaning, if you have 300 pounds per inch spring rate, it takes 300 pounds to compress that spring one inch. A 300 pounds per inch linear spring, compressed three inches, would equal a load of 900 pounds. As you can see, one progressive spring can do the work of two or more linear springs. This is a big advantage in modern automotive chassis design, fulfilling the needs of today's discerning customers.
The nice thing about Linear Springs, is that they are readily available and inexpensive, allowing most race teams to use several different sets depending on track conditions. Linear springs are also easy to work with because the spring rate never changes, allowing for quick chassis set-up. This user friendly appeal is why so many chassis tuners are critical of progressive rate springs. These chassis tuners do not have the know-how to use progressive rate springs, or if they do have the knowledge, the manufacturer that they use is not capable of producing the design specified. Springs with a high linear rate would be used on a smooth racetrack, while on a rough or bumpy road course; you would use a softer spring rate. Since many racetracks have different road surfaces a suspension that is adaptive to changing road surfaces is desired. Progressive rate springs can offer a chassis tuner the means to achieve a compliant suspension in the rough and a tight suspension for high-speed turns.
Spring Ride Height
Stock
Prodrive - .75"-1.25" Front .75" Rear
Cobb - 2" Front 1.5" Rear
Whiteline Flatout - 1.75" Front 1.5" Rear
Eibach Pro - 1.2" Front 1.0" Rear
Tein H-Tech - 1.8" Front .75" Rear
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