60 APRIL 2020 scca.com
The art of tire grooving is one that has been practiced across various
forms of rally for decades. In fact, many
dedicated rally tires have patterns and
guides for grooving based on the surface
and conditions the vehicle is about to
face. Beyond that, tire grooving is also
a useful skill for racers on a budget
who can’t afford the latest and greatest
RallyCross tire but can replicate the pattern
on a cheaper carcass. That said, before
putting any rally tire under the knife,
you need to know what you’re doing.
For the uninitiated, tire grooving refers
to the act of cutting a different pattern into
a tire’s tread. This can be performed using
several methods, but the most common
practice is to use a dedicated tool that
consists of a blade and a heating element.
The basic idea is that as the heating element
warms the blade, it will slice through the
rubber of the tread blocks allowing you to
cut the most precise pattern possible. Prices
of these tools range from $100 for the basic
versions up to $400 or more for the higher
wattage models with various temperature
settings. While not legal for SCCA’s Stock
RallyCross category, grooving is A-OK in
Prepared, Modified, and Constructors.
One of the most common reasons for
grooving a tire is to widen the void area in
the tread to help evacuate dirt and mud in
sloppy conditions. Many folks who have used
winter or gravel tires with tight tread patterns
know how frustrating it is to feel their tires
turn into gumballs as they pack with mud.
Selectively opening the void area in between
the tread blocks and toward the outside or
inside shoulder will allow the tire to eject the
mud and dirt rather than hold onto it, thus
exposing the available tread blocks to bite into
the surface. “Squaring” off the tread blocks on
a tire will also help it bite on muddy or loose
surfaces. This gives the tread blocks a sharp
edge to dig into the surface under acceleration,
deceleration, and even laterally, depending
on how aggressive you get with the cuts.
By combining these two methods of
grooving, you can take an ordinary winter
tire and turn it into a full-fledged mudder.
The key with this method is to balance the
void area with the number of remaining
squared-off tread blocks. Too much void
area results in an overall loss of traction
due to insufficient tread. Not enough void
area, or a poorly designed pattern, will still
trap mud and soil in the tire, limiting the
effectiveness of the squared-off blocks.
Selecting a tire that lends itself to
being grooved in this pattern is also
important. The Cooper Weather Master S/
T2 for example, is an old favorite for this
due to its blocky tread shape and design.
However, there are plenty of other tires
that can be grooved to suit various needs.
Other ways tires can be improved by
grooving include creating water channels
to evacuate rain, adding circumferential
grooves for the front tires to aid steering
response as well as lateral traction, and
sharpening rounded edges on tread blocks
of used tires. Some racers will also perform
this type of grooving on new gravel tires
with rounded outside tread blocks.
Done right, grooving is a great way
to get more life out of a set of tires or to
get extraordinary performance out of
ordinary ones. So, the next time you’re
eyeing some new RallyCross rubber,
remember that an equally viable option
may be just a few cuts away.
GET INTO THE GROOVE
Tire tread designs range
from all-season to rally-specific (BELOW). Picking
the right tire and tread
pattern in RallyCross
made a huge difference
at the 2019 DirtFish
Grooving your own RallyCross tires is possible, but you have to
know what you’re doing | WORDS Matt Wolfe | MAIN IMAGE Rupert Berrington