6. What are some of the guidelines for
Grooving and "Siping" Late Model dirt tires?
(Answer compiled with the assistance of driver Scott Bloomquist.)
The 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
Dirt racers 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
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.
Grooving and Wear
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. (see
Learning to 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.
Racers rarely 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 at
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. (see photo)
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.
Occasionally 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.
Though some 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.
Grooving the Tread "Shoulders" - (see
Grooving the 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.
- (see photo)
Some tracks 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.
Shapes 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.
Grooving Angles - (see
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.
Rough Race Tracks
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.
Grooving and Heat
Some tracks 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. (see
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 is.
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.
Keeping Records is VITAL
Learning the 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. (Top)
7. Does it matter which
direction I mount my Hoosier RACE TIRES? (click here)
How do I sipe or groove my Hoosier
sprint tires? (click here)
9. What are the
do's and don'ts when storing Hoosier race tires at the end of the racing
The useful life of a tire, whether mounted or dismounted, is directly
affected by storage conditions. Tires should always be stored indoors in
a dark, cool, dry room.
1 Remove the tires from the vehicle.
2. Remove the air from the tires and store them on their side in a cool/dark/dry
3. Place tires in a black plastic bag when stored during
4. Make sure the temperature range in the storage
location is between 40-90 degrees Fahrenheit.
1. Don't store tires in direct sunlight or near electric
motors. (Electric motors emit small amounts of ozone.) Tires need to be
protected from light, especially sunlight. Light causes ultraviolet
damage by breaking down the rubber compounds. The storeroom should not
contain electrical welding or any other equipment that could produce
2. Don't apply any chemical treatments to Hoosier tires.
(It's not necessary and may actually damage the integrity of the tire by
breaking down the rubber properties of the tire.) Tires must not be
allowed to come in contact with oils, greases, solvents, or other
petroleum products that cause rubber to soften or deteriorate.
3. Don't store tires in sub-freezing temperatures for
any length of time. (The rubber can freeze and may crack as a result.) (Top)
I would like to sell Hoosier tires in the US or Canada, how do I become a
Hoosier Tire Dealer?
Hoosier has an established
network of independent Hoosier Distributors. They, in turn, establish
their own network of Hoosier Dealers. You will need to contact the Hoosier
Distributor in your area who handles the particular tire line you are
interested in carrying. You will ask the Distributor whether they have a
need for a dealer in your particular location.
What are the recommended operating temperatures of Hoosier sprint tires under
various track conditions?