| 1. Tire
Pressures |
Each time the car is setup make sure to
put the tires at the pressure you will race them to make sure that any
other measurements taken are relative to how the car will be raced. |
|
2. Approximate Ride Heights |
Put the car on a level flat
surface and then set each corner to the height you want it in race trim.
Even though this step will be repeated later it is important to do it
now at this point also to ensure the next steps are accurate.
Choose whether or not to complete these steps with or without driver and
then always do it the same way for uniformity. Because this is
kids racing and they are not always to find doing without driver is the
most common. This means that comparing ride heights with other
handlers may not always be an apples to apples comparison but it will
make sure your process is consistent. |
| 3. Square
the car |
Most often this is done by taking off
the wheels and hubs and placing the car into a set of alignment bars.
While some setups result in the rear axle being slightly out of square,
for a baseline start with it parallel to to the lower roll cage bar in
front of or behind the engine. Be careful to measure precisely
using squares to your level surface for references to make sure your
measurements on each side are consistent. Even 1/16th of an inch
in variance will make a big difference. Adjust your rear radius rods
accordingly to put the axle square. |
|
4. Square birdcages |
Most brand cars are
designed so that the rear bird cages or "bearing carriers" are
positioned so that the two radius rod mounting points are directly above
/ below each other. If a line was drawn from the top point to the
bottom and continued to your level surface it would be perpendicular to
the level surface. Not being square can result in some funny rear
axle steering movement as it travels up and down. This is also
adjusted by lengthening and shortening the radius rods, again be careful
to either make equal adjustments on top and bottom or to re square the
rear axle when you are finished. |
| 5. Set Axle
Lead |
Next the front axle lead is measured by
tape measuring from the outside edge of the front axle with wheels in
straight position (if they were on the car) back to the rear axle with
the table parallel to the outside frame rail of the car. There is
a big difference is brands of cars with this setting. Anything
from from the right side shorter by a quarter inch to the right side
longer by a whole inch. This is adjustment by lengthening or
shortening the front radius rods. Making sure to adjust the top
and bottom rods evenly on the side adjustments are made. |
| 6. Set
Caster Camber |
Caster can be set with either a caster
/ camber guage or an angle finder. Use an angle finder to measure
the angle from the top of the spindle bolt to the bottom parallel to the
length of the car front to back. Right front caster is usually set
somewhere between 2 and 5 degrees. Caster is adjusted most often
by shortening or lengthening a single radius rod on that corner of the
car. Tiny adjustments make a big difference. Most front
axles have a caster split built into them so setting the caster is done
on a single corner and the LF will be what it will be. |
| 7. Set
Front Alignment |
The Toe-In / Toe-Out is set next so
that the front wheels are are parallel with each other while the car is
in the alignment bars or has the wheels on it on a level surface. |
| 8. Final
Ride Heights |
With all the wheels and tires back on
the car and back on your level surface check the tire pressures one more
time then re-measure to make sure each corner of the car is set to the
desired height. |
| 9. Wheel
Spacing |
Make sure the wheels are moved in or
out to the desired position for each corner. This usually means
the left sides are tucked in as far as legally possible (not inside the
side nerf bars) and right rear in the middle of its adjustment range. |
| 10.Scale
the car |
Using anything from accurate bathroom
scales to electronic scales put each wheel on its appropriate scale pad
and record the weights. Make adjustments to the coil spring
collars or torsion bar adjusters to each the Cross Weight or Left Rear
Split you are looking for. Make sure to make 4 equal adjustments
all the way around the car. This will ensure that the ride heights
remain where they should be.
For example if the cross weight is 50%
(LR + RF) / Total and you are looking for 54% then put 1 turn in the LR
and RF (clockwise) and take a turn out of RR and LF (counter-clockwise). |
| 11.
Practice |
Put the car and driver on the track |
| |
|
|
Ackerman Steering: |
As the front
wheels turn through the corner the left front turns a shaper corner than
the right front. Ackerman is the principle of creating steering
geometry so that as the driver turns the steering wheel the left front
will turn more than the right. Some quarter midgets have a set
amount built in to the spindle and others leave it adjustable. |
| Alignment
Bars: |
These devices are used to
line up the front and rear axles for squaring and to set the toe for the
front wheels. After the wheels are taken off the car the rear axle
and front spindles are placed into the appropriate fixture. |
| Axle Lead: |
This measures how far out
of square an axle is set in the car. Most car builders recommend
setting the rear axle with no lead so that when at ride height it is
perfectly perpendicular to the cars main frame rails. Front axle
lead anywhere from 0 to 3/4 inch is commonly found on various cars, this
would be the right side of the axle forward of the left. Front
axle lead is determined by measuring from the outside edge of the rear
axle forward to the outside edge of the front spindle and comparing the
two sides of the car. |
| Baseline
Setup: |
Refers to basic starting
points for your chassis setup and includes a setting for each of
the variables that can be adjusted. Every type of car uses
different baselines and many have different baselines for different type
of tracks based on banking, grip, surface, etc. A common practice
is to always revert the car to its baseline for the upcoming track so
you know exactly where you are when its time for adjustments. |
| Bicycling: |
This what a car is called
when it goes up on two wheels. In the center or exit of a corner a
car with too much side bite or grip can transfer enough weight to lift
the two left side tires. |
| Birdcage
Timing: |
The birdcages, or "bearing
carriers" are the free-floating pieces on the rear axle that connect the
axle to the rest of the car. For suspension systems that use two
radius rods to join the birdcage to the car frame the "timing" or bird
cage angle is important to car setup. Even after the axle is
squared it should still be checked. Most cars are designed so that
the upper and lower arms are mounted directly above one another.
This is because the shock is also connected to the birdcage and if the
timing is off then as the car goes through travel the shock mount could
rotate forward / back or up / down and create unpredictable results by
"jacking" weight onto or off that corner. |
| Body Roll: |
This is what the car does
as it is turned into and goes through the corner. How much the
body rolls does not change how much weight transfers but affects how
fast and where it transfers from and to the different corners of the
car. |
| Camber: |
Describes the angle of
each front wheel and tire if you were looking at the car directly from
the front. It is measured in degrees and can be negative or
positive. Negative camber means the top of the tire is leaned in
towards the car and positive camber means the top of the tire is leaned
out away from the car. A small amount negative camber is used on
the right front tire of quarter midgets to keep the tire from rolling
over when it gets loaded during cornering. Left front tires are
usually straight up or have an smaller amount of positive camber.
Some cars have specific camber adjustments in their spindles and others
are adjusted by using different sized tires on the two sides. |
| Caster: |
This is angle of the part
of the front spindle that it rotates around. Looking at the
spindle bolt or "king pin" from the side of the car. If the top is
leaned backwards it is known as positive caster and if the top is leaned
forward it is negative caster. Too much positive caster and the
car will be hard to turn, not enough and it can be very "twitchy" or "darty"
for the driver. Most quarter midget axles have a "caster split"
built into them of 2 to 5 degrees or so, so that more positive caster
can be run on the right front and less positive, 0, or even a small bit
of negative caster on the left front. Besides providing tracking
and driver feel caster does two other important things. When
wheels are turned with caster in them the ride height for that corner is
changed so the corner weight is adjusted or "jacked". In addition
negative camber is added or "gained" as a wheel with positive caster is
turned. |
| CG Height: |
Center of Gravity Height,
refers to the center mass of the car. The higher the CG Height the
more body roll will occur. Most important at two points, directly
above the front and rear roll centers. If a line was drawn from
the front CG Height and rear CG Height it should be parallel with a line
drawn between the front and rear roll centers to provide unbound body
roll. |
| Corner
Weights: |
When setting up the car it
is important to set the corner weights. This means actually
weighing each corner of the car on a scale adjusting them by changing
the ride heights for each corner. Every car manufacturer has
different recommendations for their car that should be followed
depending on the springs and shocks that are used. |
| Cross Weight: |
This term refers the
percentage calculated by adding the diagonal combination of left rear
and right front corner weights and dividing by the entire car weight.
Depending on whether the car is locked or not and depending on
how much it is using the LF tire changing the cross weight will either
tighten or loosen the car up. Different cars react different. |
| Durometer: |
Device used to measure the
hardness of the rubber on a tire. The readings can be used to
compare different compounds of new tires or to track the life of
an existing tire that will get harder over time until it is no longer an
effective tire. |
| Gas Shocks: |
Shock absorbers or
"dampers" that have a small chamber in them filled with nitrogen to keep
pressure against the shock oil so that bubble are not created when the
shaft goes in and out. |
| Gear Ratio: |
A measure of the actual
RPM reduction from the engine to the rotating rear axle. It is
calculated by dividing the number of teeth on the axel gear by the
number of teeth on the engine gear and multiplying that by the engine's
gear box reduction ratio. For Honda engines this is 6.0 and for
DECO engines it is 5.73. For example a 30 engine gear with a 25
axel gear would be 25 / 30 * 6 = 5.00 |
| Locked: |
Refers to the type of left
rear wheel hub used. A locked car uses a hub that directly
connects the wheel to the axel while an unlocked car connects the wheel
to a hub with a free spinning wheel bearing. A locked car uses
both rear wheels to drive the car and an unlocked car uses only the
right rear. A locked car is more stable and tighter in the corners
but will scrub speed on the straights. |
| Loose: |
Describes the cars
handling when it wants to turn more than the driver is trying to turn
it. Also known as over steer. |
| Pattern: |
The line around the track
that the drivers takes the car. Low in the corner and high in the
straight for asphalt tracks. Different tracks have different
preferred patterns with small differences like how close to the wall the
car should be, how far down the straight the car should be before it
turns, and just where in the corner the driver should apex. A
driver can also adjust their pattern to accommodate the car's handling.
Different classes sometimes have different patterns because of the power
differences. |
| Panhard Bars: |
The suspension link that
locates each axle laterally in the car. One per axle, this
normally straight bar with rod ends connects on one end to the axle and
the other on the chassis frame. The center of this bar determines
both the height and left to right location of the roll center for that
particular end of the car. |
| Push /
tight: |
A car with this handling
condition does not turn as much as it should. Its hard to get down
to the bottom of the corner in the middle and hard to keep off the wall
coming out. It results from the rear tires having more grip than
the front. In addition to being hard to keep off the wall this
condition can also bog down the motor exiting the corner. |
| Rake: |
The difference in ride
heights from the back to the front of the car. Positive rake means
the rear of the car is higher and is common for asphalt tracks. |
| Rear Split: |
The difference between the
two rear corner weights. Expressed as a single number it is
usually expressed as how much more the left rear corner weighs than the
right rear. Negative rear split would means the right rear corner
weighs more than the left rear. |
| Ride Heights: |
This measurement describes
how far the bottom of the chassis from the ground. It is taken at
each corner of the car. Some manufacturers recommend taking from
cross tubes whiles others measure directly from the underside of the
frame. It is important to track and maintain proper ride heights
so the chassis geometry stays as intended. |
| Roll Center: |
The imaginary point of the
chassis that it pivots "over" as is rolls into and our of the corners.
Each car has a front and rear roll center. For most QM suspension
types it is determined by find the center of the panhard bar for each
end of the car. Typically raising the roll center results in less
body roll and loosens the car while lowering it lets the body roll more
and tightens it up. |
| Scaling: |
Process of determining how
much static weight is on each corner of the car while it is just sitting
there. It is done by sitting the car on four individual scales or
scale pads. |
| Scrub
Radius: |
The imaginary line between
the center of a front tire contact patch and the axis that it pivots
around when the wheel is turned. Newer cars tend to have a much
shorter scrub radius that results in easier steering and potentially
less speed "scrubbed" off through the corner. |
| Shock Valving: |
The inside make up of a
shock that determines how easy or hard it is to push it in or extend it
out. Straight valved shocks are the same in both directions while
split valve shocks require different levels of force to move them in
from moving them out. The higher the shock number the stiffer it
is 'valved'. Shocks determine how fast weight is transferred from
corner to corner in a car, now how much weight is transferred.
Heavier valved shocks are typically required for heavier and faster
cars. |
| Spring Rate: |
The wire thickness, coil
diameter, and number of coils a spring has determine the rate of a
spring. It is measured as how many pounds of force are required to
compress the spring one inch. |
| Squaring: |
Process of making sure the
rear axle of the car is perpendicular to the frame of the car and that
front axle is parallel with that. A axle accidentally out of
alignment will cause undesired steering. |
| Stagger: |
Difference in
circumference between the two rear tires. When the rear axle is
locked up it is important to have the proper amount of stagger so that
the rear tires can work together through the corner and not fight each
other and scrub speed. Since the outside tire has to go around a
bigger circle it requires a bigger size because the same axle is turning
both tires at the same time. |
| Sway Bar: |
A rigid bar that connects
one corner of the of the suspension to the other on the same end of the
car. Also called an Anti-Roll bar its purpose is to provide roll
stiffness to lessen the amount of body roll into and out of a corner. |
| Tilt: |
The difference in ride
heights from the right side of the car to the left side. Positive
tilt means the right side of the car is higher than the left.
Negative tilt would mean the left side is height. A car with 1/8
inch of tilt would mean the right side of the car is 1/8 inch higher
than the left. |
| Tire
Compound: |
Type of rubber used to
construct the contact surface of the tire. Every manufacturer has
different letter codes to designate the hardness and type of rubber.
Softer tires are stickier and provide traction faster but will wear
faster and can become too sticky. Harder tires last longer but
take longer to "come in" and don't always provide enough traction.
The right tire depends on the track surface, class of quarter midget,
and chassis setup used. |
| Tire
Pressure: |
Measurement of how much
air is in the tire, expressed in pounds per square inch or PSI.
Right side quarter midget tires on asphalt are typically between 10 and
15 psi while left sides are typically below 10. |
| Tire Temps: |
Handlers will often
measure and record the surface temperature of the contact area of each
tire when a practice or race run is completed to help them make setup
adjustments to balance the chassis. Extreme temperatures on a
single tire usually indicates a setup that is not balanced. |
| Toe In / Out: |
"Toe" refers to one of the
front wheel alignment adjustments. Looking at the front wheels
from the top of the car if they are parallel to each other then the toe
is set to zero, the most common setup for a quarter midget. Toe In
means the front of the tires are pointed to each other and Toe Out means
the front of the tires are pointed away from each other. Too much
Toe either direction will scrub speed from the car but a slight bit of
Toe Out can provide some steering stability, especially for newer
drivers. |
| Torsion Bar |
A rigid bar that is
mounted on each corner of the car so that when the chassis goes up and
down it twists and absorbs force like a coil spring does. Very
common on dirt cars and older quarter midgets. |
| Weight
Percentages: |
Used to record corner
weights when scaling a car. Left side percentage, Rear percentage,
and Cross Weight are all calculated by adding the two appropriate corner
weights and dividing them by the total. |
| Wheel
Offset: |
Used to describe how a
particular width wheel is divided between its "inside" and "outside"
halves. For two piece wheels its is the width of each half while
one piece wheels are described by their total width and the distance
between the plate where the hub mounts and the inside edge. For
example an 8 inch wheel with a 3 inch backspace. |
| Wheel
Spacing: |
Refers to where the wheel
is positioned on its axle in relation to inside or out. Right rear wheel
spacing is a common adjustment for then handling of the car.
Moving that wheel in tightens the car while moving it out can loosen the
car. |
