Toe
Toe is a word that describes the angle of a particular wheel, relative to the centerline of the chassis. Toe
in refers to when the front edge of the wheel is closer to the centerline than the rear edge of the wheel.
Toe out refers to when the rear edge of the wheel is closer to the centerline than the front edge of the
wheel.
Front Toe
Front toe is adjustable by lengthening or shortening the steering turnbuckles. Front toe should ALWAYS
be set after your camber and chassis heights have been set. Front toe is typically measured using a
ruler, calipers, or other measuring device. In general, I like to consider front toe as a setting, rather than
an adjustment. Although you can adjust your front toe to be toed in, neutral, or toed out, I like to keep
things simple by always running a very slight amount of front toe out. For 1/10th scale cars, I run 1/16” of
toe out (.063”). For 1/8th scale cars, I run 1/8” of toe out (.125”). Again this is something I use as a
setting, and I literally never adjust the amount of front toe; however you must check your toe after each
camber, chassis height, caster, or camber link adjustment. All of these adjustments play a role in what
length steering turnbuckles you must have for proper front toe.
If you decide to tune with front toe, here is a basic guide to what each adjustment does:
Front Toe In – Less turn in steering, more exit steering, more aggressive down the straights, sometimes
twitchy or darty feeling.
Front Toe Out – More turn in steering, less exit steering, more balanced down the straights, usually the
most comfortable feel.
Rear Toe
Rear toe is adjustable by changing the rear toe blocks and/or the holes through which they mount to the
chassis. Rear Toe is measured in degrees. In general, the more toe in you run, the less overall steering
you will have. The lesser the amount of toe in you run, the more overall steering you will have. In dirt
oval cars, rear toe technology has evolved greatly over the past 4-5 years. Now it is somewhat common
to run up to 6 degrees of left rear toe in, and sometimes racers even run right rear toe out! One very
tricky aspect to tuning your dirt oval chassis and its rear toe in setting is that each corner affects the car
differently.
Left Rear Toe
Left Rear Toe is ALWAYS run toed in on today’s dirt oval chassis. Typical amounts of RR Toe in are
between 0 and 6 degrees. In general, we use the LR toe angle to adjust how the car ENTERS the corner.
The more degrees that the LR is toed in, the more rotation the chassis will have on corner entry, both on
and off power. The fewer degrees that the LR is toed in, the less rotation the chassis will have on corner
entry. Foam tire setups often run between 1-3 degrees of LR Toe in, while Buggy tire setups often use 4-
6 degrees of LR toe in.
Right Rear Toe
Right rear toe is usually set at fewer degrees than the LR, and sometimes in extreme conditions, is even
run toed out. Typical amounts of RR toe are between 3 degrees of toe in and 3 degrees of toe out. In
general, we use the RR toe angle to adjust how the car EXITS the corner. The more degrees that the RR
tire is toed in, the more forward drive, and less on throttle rotation the car will have. The fewer degrees
that the RR is toed in, the less forward drive, and more on throttle rotation the car will have. Foam tire
setups often run between -1 to +3 degrees of RR Toe, while Buggy tire setups often use 0-4 degrees of
RR toe in.
Rear Toe Cheat Sheet:
Tight on Entry – Increase LR Toe In
Loose on Entry – Decrease LR Toe In
Tight on Exit – Decrease RR Toe In
Loose on Exit – Increase RR Toe In
Camber
Camber is the angle of the wheel and tire in relation to the ground or flat surface. This is measured using
a Camber Gauge. If the tire leans in towards the centerline of the chassis at the top it has negative
camber. If the tire leans out at the top it has positive camber. The camber link controls the position of
the wheel and tire as it moves up and down through its suspension travel. Camber is adjusted by
lengthening or shortening the camber link turnbuckle until the desired camber angle is achieved.
Camber has a tremendous effect on how the tires react and provide grip on the surface you are running
on.
Foam Tires
With foam tires, the tire has a consistent density throughout the tire, and running higher camber angles
will usually increase tire wear and create a wear situation known as “coning”. This situation also results
in a reduced amount of traction for that particular tire. With foam tires, the goal is to set your camber so
that all 4 tires wear evenly. My foam tire cars usually have the tops of both front tires leaning towards
the right, and the tops of both rear tires leaning to the left. I read my tire wear after each run, and adjust
my camber link length accordingly, in an effort to have all 4 tires wearing flat.
Rubber Tires
With rubber tires, the tires have foam inserts which act like air pressure, and often gain more grip when
the camber settings force the tire to transfer the cornering forces to the inside edge of the tires. More
negative camber on the right front wheel produces more steering and is more responsive. Less negative
camber on the right front will have less steering but will be smoother. To a point, more front positive
camber on the left front wheel will give better steering into and out of a turn. Less positive camber will
similarly smooth out the steering but be less responsive. Typically, with rubber tires, all four wheels will
have the top of the tire leaning to the left.
Camber Cheat Sheet:
Foam Tires
LF – Negative 1*
RF – Positive 1*
LR – Positive 1*
RR – Negative 1*
Rubber Tires
LF – Positive 1.5*
RF – Negative 1.5*
LR – Positive 2*
RR – Negative 2*
Caster
Caster is the angle of your kingpin relative to an imaginary line perpendicular to the chassis plate. If you
were to look at your chassis, and draw an imaginary line through the middle of your kingpin, and then
measure the angle between the kingpin and a line perpendicular to the chassis plate, the measured
angle would be your caster angle. Total caster is figured by adding your kick-up angle and your caster
block angle, to come up with total caster. We will get into kick-up in a later chapter, but for now, we will
focus on total caster and its effects on chassis handling.
What Does Caster Do?
Caster affects the handling of your chassis in two ways: Straight Line stability and Camber increase as
steering input is given.
Straight Line Stability
The higher degree of Caster you run, the more the car will want to stay straight while driving straight.
The lesser degree of Caster you run, the more the car may want to wander while driving straight.
Typically, more caster is better for straight line stability in low bite conditions and less caster can keep a
car from feeling numb in high bite situations.
Camber Increase via Steering Input
As you turn the wheels, the angle of Caster affects the angle of camber. The greater the amount of
caster you run, the more camber you will gain with steering input. The lesser the amount of caster you
run, the less camber gain you will achieve with steering input. Generally speaking, as you increase
caster, you will gain steering as a result of increased camber. This is not an absolute scenario however;
because if you have too much camber gain, you can actually reduce the amount of traction that a
particular wheel can make causing the tire to be overloaded and slip. In some conditions, Caster may
need to be reduced, to reduce camber gain via steering input, in order to increase contact patch on a
particular corner which can result in improved grip for that particular tire. Like any adjustment, too
much caster can be a bad thing. The goal when tuning with caster is to find the ideal handling
characteristics both in a straight line and while cornering.
Caster Split
Caster Split is the difference between LF and RF caster angles. Typically, I suggest no more than 5
degrees of Caster Split. Five degrees of caster split is achieved by running 5 degrees less caster on the LF
than the RF. Caster split helps the car turn into the corner easier, and in most instances, increases mid
corner steering. Caster Split usually allows a racer to run less steering throw or dual rate, which in turn
reduces corner speed scrub. In some extreme situations, racers have been running very aggressive rear
toe settings, and in order to make these setups easier to drive, have been running negative Caster Split.
Negative Split is when the RF has less caster than the LF. I suggest that racers keep caster adjustments
simple, and run either 0 or 5 degrees of caster split for a balanced, easy to drive race car.
Wheel Spacing
Wheel Spacing is an easy way to change the way your chassis drives, without changing the balance of
your chassis. Front Wheel Spacing has a greater effect off power during corner entry, while rear wheel
spacing has a greater effect on power during corner exit.
Front Spacing
In general, as you space your front wheels to the right, you tighten up corner entry. Spacing your front
wheels to the left will free up your corner entry.
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Tighter entry = easier to drive but less potential for corner speed
Freer entry = harder to drive but more potential for corner speed
Rear Spacing
In general, as you space your rear wheels to the right, you free up corner exit. Spacing your rear wheels
to the left will tighten up your corner exit.
Tighter exit = More forward drive and less on throttle rotation
Freer exit = More on throttle rotation and less forward drive
Chassis Tuning 101
Matt Murphy’s Dirt Oval Chassis Tuning Guide