are some of the guidelines for Grooving and "Siping" tires
one thing every racer has to remember is that the tires are the
only link between the chassis, engine and track, and an otherwise
perfectly set up race car can not perform up to it's potential.
have to pick the right tire compound much like an asphalt racer,
but there is another important step to getting the most out of a
dirt tire. Dirt racers often have to alter the design of a tread
pattern to best work with the conditions at a particular track,
on that day and with their driver's style or habits. We can't tell
you exactly the specific kind of grooving that will work best for
your situation, but we can provide basic information to make you
better able to decide for yourself as you encounter different racing
We also have
to consider the abrasion of the track, how wet or dry the track
is and if the track contains rocks or other debris that will tear
up the tire. All of these conditions must be considered when deciding
on what kind of groove to use, how deep to cut and how many grooves
can be out without causing the early demise of the tire. Along with
these factors racers must consider the amount of heat a track puts
in their tires. In addition to enhancing traction, grooving helps
the tire dissipate heat and can be used to help control tire temperatures.
Any time a groove
or sipe is cut into a tire it accelerates wear. The trick is to
balance the benefit of grooving with the increased wear. One of
the reasons we sipe a tire is to prevent the tread surface from
glazing over and becoming slick. Sipes keep the surface wearing
and the tire working throughout the race.
recognize the amount of wear you can expect from a track not only
helps you choose the right compound tire for the night but is important
information for deciding what pattern and depth grooving to use.
The object is to maintain the highest level of traction throughout
the race without wearing the tread off of it with five laps to go.
With an understanding
of the basics of grooving tires racers will be able to look back
on their experience with the tracks they have raced on and make
better decisions on what type of grooving will help them most. Keeping
records of the results of your decisions is the best teacher, so
if you are not already keeping a "book" on each track,
start one now.
run soft tires in a race, especially the 100 lap events, but grooving
soft tires correctly can be a big help in qualifying or short heats
on a wet track. Softer tires are generally used on tracks that have
a lot of moisture but not a lot of abrasion. You may also use a
soft tire on a surface that does not generate a lot of heat in the
tire and may have loose dirt or clay on the surface throughout the
race. Cutting more grooves can help clean away loose dirt, plus
improve traction because of the increased number of edges available
to dig into the tracks surface. On tracks where you are not moving
or throwing any dirt, but the surface is still relatively soft,
a soft tire can often be run effectively with little or no grooving
Keep in mind
that grooving not only increases traction, but increases the rate
at which a tire wears. A soft tire will begin losing it's traction
sooner as the amount of grooving increases. The softer material
naturally tears easier and fatigues sooner, causing the tire to
slow down. On a surface with a lot of traction or if it contains
rocks and other debris, the tire will tear up much quicker with
excessive grooving. Determining the correct amount and style of
grooving comes with experience and watching how the tire wears and
what the driver felt s the race goes on.
One of the things
we do with soft tires is only groove about half way across the blocks
to prevent weakening the structure too much. With the large stagger
block tread design we can often run that tire with little or no
additional grooving, depending on the condition of the track. Usually
we will run that pattern on all four corners on a wet track.
when we run a ribbed tire on the right rear and do the grooving
ourselves, we will follow the groove lines the factory put on the
tire and then wait to see if the tire is going to start tearing
and how many laps it takes for the tire to start working well. If
the tire needs a couple of laps before it starts working we may
add some grooves or sipes to give the tire a little extra grab until
it develops enough heat to work on it's own.
harder tires may withstand grooving better than the soft compounds,
the track conditions that made you choose a hard tire may not require
much in the way of grooving. In the South we often do not groove
the harder tires much at all. In fact, there are some tracks that
pack down to where they are similar to asphalt and we have run tires
with no grooves at all. We leave the tires full slick.
the Tread "Shoulders"
shoulders can be helpful if you plan to run the high line or on
a cushion and need to be moving some dirt. Grooves on the shoulders
help clean away some of the loose dirt to get at moisture beneath
it. Sometimes the outer row of blocks is also grooved on the right
rear to work with the shoulders.
On some of the
harder natural rubber tires we sometimes sipe the shoulders. This
can really help when you are rolling the tire under when running
lower tire pressures on a very slick track. The sipes can help prevent
the shoulder area of the tire from glazing over and losing traction.
The shoulder is as important a part of the tire as anything else
and if you are going to be running on it due to low air pressure
or because you are running against the cushion you need to make
the best use of it.
do not have a lot of abrasion to them and edges on the tire can
increase traction considerably. When we get on a surface like that
we will use wider grooves to present a cleaner, more prominent edge
to the racing surface. Narrow grooves may not have enough distance
between edges to allow them to work properly.
On some tracks
you can groove the tires twice as much with a narrow groove, or
half as much with a wide groove and accomplish the same thing. It
depends on the track surface and how abrasive it is or if it contains
rocks that will tear the tire up. You don't want a lot of grooves
on a rocky or highly abrasive track. Fewer, but wider grooves stand
up to these harsher conditions better.
of the Grooves
There are three
basic shapes used in grooving: square, V, and sipes. Square grooves
are the same width through it's entire depth. V grooves start out
wide at the top and taper to nothing at their bottom. Sipes are
thin slits cut by installing the blade upside down in the holder
and using the separate ends of the blade to cut slices in the tire.
All three types
of grooves can be used in various depths depending on conditions
and the length of the race. The V groove is often used when the
track is expected to need more tread contact later in the race.
As the tire wears, the grooves become smaller or disappear completely.
Square grooves can be used the same way but the extra width could
provide enough leverage for an abrasive track to tear the tire if
the track becomes abrasive.
Siping is usually
meant to make the tread more pliable and does not produce the edges
square or V grooves do. Siping also helps the tread maintain a more
consistent wear that helps keep the tire working uniformly.
The angle at
which grooves are cut determines how much of the edges are exposed
to the track when the car is in various degrees of slide. Dirt race
cars seldom if ever run in a straight line but the driver will try
to keep the car much straighter when the track is slick than when
there is a lot of bite to work with. When the track is slick we
keep the grooves pretty straight. But when we spend a lot of time
with the car sideways we put more angle into the grooves.
How much of
an angle is dependent on the drivers style and experience is the
only way to determine the best angle for your situation. The idea
is to keep the maximum amount of the tires edges facing the direction
the tire is actually traveling. As a dirt car travels around the
track on a given line, the body is actually pointed towards the
infield a certain number of degrees. If the driver is consistent
you can determine an angle for the tire grooves that will work best
for your combination.
We almost always
cut circumference grooves in our front tires because they help make
the tread blocks more flexible which increases traction and helps
the steering. Here also the width of the groove is determined by
individual track conditions.
At some tracks
we will also sipe across the circumference grooves so that we are
making little blocks that are more flexible yet. These smaller blocks
can help a lot when you catch little rough areas on the track.
We have found
that as the roughness of a track increases, so does the need for
grooves. Unless the track surface is very smooth, some sort of grooving
is likely to be necessary to be fast. When you groove a tire more,
it makes the tread surface much more flexible. It can then follow
or shape itself to the surface much better to provide the maximum
amount of bite possible.
naturally put a lot of heat into a tire and can actually cause the
tire to melt or blister. On these kinds of tracks we have found
that grooving helps cool the tire. The grooves (and sipes) help
move air across the tires surface which keeps the tread temperatures
down. Grooving also produces more surface area which helps transfer
the heat out of the tire to the air. You have to balance grooving
with the amount of abrasion or traction available because tracks
that generate a lot of heat may also be very abrasive or contain
rocks that want to tear the tire up if it is grooved too much. Too
much grooving or siping on a high traction (or abrasive) track can
cause the tire to start tearing up very early in the race.
To help a tire
dissipate heat without weakening the tread blocks too much we will
cut grooves in the center of each block instead of cutting all the
way across it. We have even made a tool for drilling a circle in
the middle of individual blocks to help cool without weakening the
blocks structure too much. This kind of grooving works well when
you want as few grooves as possible for speed but need to increase
cooling to prevent blistering.
The number of
laps to be run is an important consideration when deciding how to
groove your tires. Softer tires may be used in shorter races of
25 to 40 laps and you will have to be careful about removing too
much rubber which may cause the tire to wear out prematurely. Accelerated
wear caused by excessive grooving can be a problem with harder tires
normally used in 100 lap races depending on how abrasive the track
We try to decide
how much wear we expect on a particular track, then adjust our grooving
accordingly. Often we will groove only half way into the depth of
the tread so as the races progresses and the track turns smooth
and abrasive normal tire wear produces very shallow or grooves that
begin to disappear. Then when we need the most rubber on the track,
the grooves are just about gone.
Records is VITAL
tracks on which you race and how they change over the course of
an evening of racing will go a long way in helping you learn to
groove tires. Keep track of how your last grooving ideas worked
with the condition of the track surface. What were the other guys
doing that drove past you? Read your tires after the race to see
if another style or amount of grooving would have worked better,
then write it down so you will have that information the next time
you are in a similar situation.
Much of learning
to prepare and drive on dirt surfaces comes from experience and
applying that information to your current situation. You may spend
some time writing down what DIDN'T work, but that puts you closer
to what WILL work to make you faster