Tire stagger is the difference in circumference between your right side tires and your left side tires. In oval
dirt track racing the right side tires are bigger than the left. This helps the racecar turn to the left. A good
example of this can be seen by using a tapered styrofoam cup. Set the cup on its side with the open end to
your right and the bottom to your left… push the cup. The cup will roll in a circle to the left, just like your oval
track racecar should. More importantly than that, the rule of thumb on dirt tracks for how much stagger to use
depends on the track surface. If the track surface has bite, this could be a heavy tacky surface or a surface
that has rubber, use more stagger. If a track surface is dry, slick and loose use less stagger. The actual
amount of stagger will depend on what your chassis builder suggests as a starting point, then simply adjust
from there according to track conditions.
Springs and Torsion Bars
The following section pertains to “offset chassis” such as dirt style center seated modifieds, sportsman, sprint
cars, midgets, mini-sprints, ect. With these type of racecars your left side springs should be heavier rated
springs. The reason behind this is directly related to the “offset” of the racecar. The left side of these type
racecars has a shorter distance from wheel to frame than the right side. Being that the racecar is “offset” the
greater amount of chassis weight is concentrated there, therefore the spring on the left side has to supports
greater weight than the right. The difference in left and right side springs also attribute to chassis handling,
by allowing the racecar to “transfer weight” when entering or exiting a corner or when accelerating or
decelerating.
Spring Rods
This section we start with a warning for new or inexperienced drivers. Spring rods can accentuate a push or
loose condition and may make a new driver uncomfortable and reduce the possibility of consistent laps. A
driver should get comfortable with a solid rod and then after some experience move to a spring rod set-up.
Spring rods allow the right rear tire to “drive forward” shorting the right side wheel base for a short period of
time and pointing the rear wheels towards the inside of the track. This combination of effects tightens a
racecar while under acceleration and can improve drive off of a corner.
To make a spring rod adjustment, first measure the length of your spring rod. There are two washers, one on
either side of your spring rod. Make sure to measure the same way each time, measuring from the inside of
one washer to the inside opposite washer will tell you the length of the spring itself. Most modified chassis
manufacturers suggest starting at 3 ¾ inches. Now, to make an adjustment loosen the setscrew located in
the jam nut against the spring. Then adjust the jam nut in or out depending on the adjustment you are
making. Check your measurement until you have reached the desired length. Make sure to have the
setscrew lined up with the flat spot of the threaded rod, and then tighten the setscrew.
Spring rod adjustment varies similar to that of stagger. On a track surface with bite, like a heavy tacky track
or a track with rubber, shorten the spring of the spring rod, this allows less travel and will reduce the chance
of a push on exit. On a dry, slick or loose track, lengthen the spring of the spring rod, this allows more travel
and will reduce the chance of a loose corner exit. Make sure to make small adjustments with your spring rod
as even a ¼ inch in or out can make a noticeable difference in handling.
Radius Rods
Radius rods are female threaded rods, usually made from aluminum or steel, which work in conjunction with
suspension components. The rod ends or heim joints provide a pivot point that allows the rod to work on a
“radius” and even allow for some side-to-side movement.
When assembling rod ends into radius rods be sure to first treat the threads of the rod ends with never seize.
Also, make sure to run the rod ends into the rod an equal distance on each end. When mounting the radius
rods to the racecar be sure to have each rod going in the same direction. For example, each rod has a
marking that indicates the left hand thread end. If you assemble your racecar so that each left hand threaded
end is pointing towards the front of your racecar you will have consistent loosing and tightening directions on
each rod. For those radius rods that work as pan hard rods follow the same rule of thumb, mounting all in the
same direction. All of these processes will allow for easier adjustment when needed.
Here are a few tips on making radius rod adjustments. Be sure your radius rods are well maintained, cleaned
and properly lubed. After washing your racecar the use of a WD-40 type product right after cleaning will force
moisture out of the ball and socket of the heim. Then lubricate and make sure you have good movement.
When tightening the rod end to the rod the use of a 9/16 open-end wrench on the flat spots of the heim to
avoid twisting of the ends.
