- Joelís Bench: On-Road Suspension Essentials -
Tune to win!
Words: Joel Johnson
competition touring cars have the most
adjustable suspensions ever and can be finely
honed to any track and surfaceóif you know
what youíre doing.
Many drivers just donít know where to begin
when itís time to fix a handling problem or
get a little more out of a setup that works OK
but isnít fast enough. In most cases, all
you really need to know are the basics:
camber, caster, toe and ride height. When you
understand these essential elements of
suspension tuning, youíll be on the fast
Camber is the angle of the tires in relation
to the track and is the most basic adjustment
that any racer can make. It is measured in
degrees. When you look at the car from the
front or rear, the tires are not perpendicular
to the ground; they are typically angled in
slightly toward the chassis. When the tires
lean toward the chassis, thatís negative
camber. When the tires lean outward, thatís
positive camber. Adding a few degrees of
negative camber increases a tireís contact
patch when cornering; the tire stays flatter
as the suspension rolls due to the cornering
HOW IT IS ADJUSTED.
Camber is usually adjusted by changing the
length of the upper arm on the suspension or
the camber link. One to 2 degrees of negative
camber is generally all that just about any
race car needs. Exceptions to this rule come
into play only in extreme conditions.
Negative camber means the tires are tilted in
at the top (toward the chassis). This is most
common setup for any race car. The camber
setting should be dictated by how the tires
wear. Hereís what to look for to adjust
camber properly: if the tires wear more on
their outside edges, and negative camber
should be added. Adding negative camber on the
front of a car can increase steering, but 1 or
2 degrees of extra negative camber (beyond the
setting that causes the tires to wear flat) is
all you should add.
Positive camber is when the tires are tilted
out at the top (away from the chassis). This
setting is very rarely used, but you should
know the term. If the tires wear too much on
their inside edges, the car has too much
negative camber; positive camber should be
dialed in. When I used a solid axle in the
rear of my Trinity Reflex NT, I had to run
about 4 degrees of negative camber to keep the
tires wearing flat. This was necessary because
of the camber rise in suspension and the tire
wear that a solid axle causes.
I always adjust my camber so the tires will
wear flat and leave it set up like that
because there are many other ways to get more
steering. If you look at the tire wear and
then adjust the camber so that the tires wear
flat, you have set the proper camber for your
Most electric cars use a turnbuckle as
the upper suspension link. This is
where you adjust the camber by turning
the turnbuckle to shorten or lengthen
the upper link.
this is an example of negative camber.
Notice how the tire leans in towards the
Right: this is an example of positive
camber. Notice how the tire leans away from
this is an example of negative caster.
The axis on which the spindle pivots
is angled towards the rear of the car.
to change the caster on a pivot-ball
suspension, just change the position
of the clips from the front of the
upper A-arm to the rear of the upper
A-arm or vice versa.
Caster refers to the angle of the front kingpin or the
angle formed by the suspensionís steering-knuckle
pivots; its adjustment depends on the carís design.
Measured in degrees, caster is much more of a handling
adjustment than camber is, and smart racers make this
adjustment more often. The most common position of the
kingpin in all setups is negative caster; that means
that the top of the kingpin leans toward the rear of
HOW IT IS ADJUSTED.
Electric cars generally require a front caster-block
change to alter the angle of the A-armís hingepin
mounts. On most nitro touring cars, caster is added or
subtracted by sliding the top A-arm back and forth on
Caster directly affects how a car turns by changing
the size of the contact patch as a tireís steering
angle changes. Adding negative caster will yield more
high-speed steering and on-power steering while
reducing the low-speed and off-power steering.
Negative caster will also cause the car track much
straighter than when no steering inputs are applied.
In general, larger tracks require more caster and
short, tight tracks require less.
Positive caster is when the top of the kingpin is
angled toward the front of the car; this setting is
BEST BET. I
recommend that you start with the caster thatís
suggested in the kit setup and work from there. If you
stray from the kitís setup, to dial in the true
amount of caster, you must consider the angle of the
front A-arm and then add that degree measurement to
that of the caster block. For example, if the
suspension arms have 10 degrees of kick-up and you
install 10-degree caster blocks, youíll have 20
degrees of total caster. Depending on the design of
your touring carís suspension, measuring the exact
caster might require a setup board. When you get
serious about racing, a setup board will be necessary.
When checking ride height, be sure to
always measure from the same location
on the chassis. Also make sure the
chassis isnít worn in the area you
choose to measure as this will throw
off your measurement.
Ride height is the gap thatís between the bottom of
the chassis and the ground.
HOW IT IS ADJUSTED.
Ride height can be changed by adjusting shock preload
by installing spacers inside the shocks, or by using
downstops (aka ďdroop screwsĒ) in the suspension
LOWER RIDE HEIGHT.
In most situations, you want to run your car as low as
the rules will allow. Lowering it lowers its center of
gravity (CG), and that generally make it handle
better. This is especially true on high-traction
tracks because a lower ride height helps to control
the chassis roll from side to side.
HIGHER RIDE HEIGHT.
The only time you would want to increase the ride
height is when you run the car on low-traction
surfaces. The higher CG of an increased ride height
causes the car to roll more from side to side. This
transfers more weight to the wheels on that side of
the car, and additional weight on a tire equals more
BEST BET. To
change the handling, some racers adjust the ride
height so that itís different in the front and rear.
By raising the front of the car, more weight will be
transferred to the rear of the car when itís under
acceleration. This additional forward traction causes
the car to steer less when it exits turns. Running the
front ride height lower than the rear will have the
opposite effect: more on-power steering when the car
exits the turns. This is simply the effect of weight
being transferred from the front to the rear instead
of from side to side.
There are many other
factors involved in tuning a sedanís suspension, but if you learn
and apply what each of these adjustments does to the carís handling
in relation to your driving style, then youíll be well on your way
to tuning your car like a pro.
Toe-in and toe-out are used on the front and rear of
any touring car. Toe adjustments dramatically affect
handling. In the front, toe-in or toe-out changes the
The easiest way to spot this adjustment is to look at
a car from the top. If the fronts of the tires point
toward one another, the car has toe-in. Conversely, if
the front of the tires point away from one another,
there is toe-out. On a 4WD car, the typical setup is
toe-out in the front and toe-in in the rear. Toe-in
and toe-out are measured in degrees; they are referred
to numerically, but not as positive and negative.
HOW IT IS ADJUSTED.
Front toe is typically adjusted either by shortening
or lengthening the front turnbuckles by the same
toe-in at the front of a car allows it to react more
quickly when itís off-center, and it can cause it to
wander while running straight.
TOE-OUT. When its
front wheels toe out, a car will generally track
straighter and initial turn-in will be decreased.
Toe-out gives the car a more forgiving feel and is the
preferred touring car setup.
BEST BET. In
general, 4WD cars run about 1 degree of toe-out or
toe-in. When checking the "toe" on the front
of a 4WD car, make sure that you pull on the front
edge of the wheels to take out any slop in the
steering linkage. When a 4WD car accelerates, the
front tires are pulled toward the rear of the car by
the force of acceleration.
toe-in is usually set by the arm mounts, and
can only be adjusted by installing different
mounts. Pivot-ball cars are the exception. To
accurately set rear toe on a pivot-ball car, a
setup board (like the one shown below) is a
high-quality setup board with measuring tools
is an essential part of any serious racerís
set. You should use these before every event.
In the rear, toe adjustment usually ranges from zero
to 5 degrees of toe-in. Modest toe-in at the rear
gives you the best of both worlds, but with rear
toe-in, you must consider ďdrag.Ē The more wheels
are angled, the more drag you will have; drag
contributes to lower straightaway speeds and reduces
efficiency. The most efficient setup is the one
without any rear toe-in (to reduce drag), but this is
very rare. In most setups, there is at least 1 degree
of toe-in, if not more.
HOW IS IT ADJUSTED.
The way toe-in is adjusted differs from car to car.
Some sedans require a change of the rear hubs; in
others, the inclination of the rear A-arm hingepins
can be adjusted so the whole arm is swept forward. On
most nitro touring cars, the length of the rear pivot
ball on the bottom A-arm is adjusted. I suggest that
you stay away from changing the rear hingepin
inclination because that changes more than just the
Adding toe-in will increase the on-power forward
traction, but it wonít affect off-power lateral
traction, or ďsidebiteĒ (as some call it). This
means that when you enter a turn off-power, the car
will generally rotate as well as or better than a
setup with less rear toe-in, but when you apply power,
the car will track straight. With that setting, it wonít
finish the turn as well as a setup that has less rear
rear toe-out. I have yet to see a car that runs any
rear toe-out. Adding it will result in a highly
BEST BET. When
adjusting rear toe-in, stick with changing the rear
hubs or adjusting the angle of the rear hubs or the
pivot ball. If you need more forward traction, add 1
degree of rear toe-in at a time, and then run the car
to see the difference. In general, this adjustment
usually stays between 1 and 4 degrees.