Dirt track racing is extremely...
Dirt track racing is extremely popular, and rightfully so. The tires are vitally important to how well a driver is going to perform at the track. Photo by Kevin Thorne
What I loved most about living in Missouri during my teenage years was that I could point my car in any direction on a summer weekend night and drive for one hour and end up at a dirt track. Whether I ended up at Monett Speedway, Bolivar Speedway, Springfield Speedway or Wheatland (now Lucas Oil Speedway) didn't matter.
Dirt track racing gets my vote for the most exciting racing out there. Not to say that pavement racing isn't exciting, but there is just something about watching an 800 horsepower Dirt Late Model get thrown sideways by the driver as he mashes the gas, which picks the left front tire off the ground as the car rockets off the corner, only to repeat the action on the next corner.
The tires used for dirt racing, regardless of class, go through some extreme conditions, with ruts in the middle of the turns, spots that are wetter than others, not to mention the car being sideways while experiencing all this. Dirt racers not only have to consider what compound to use, but also what groove they want to use in the tires. Most tires will have some type of grooves cut into the tire that not only assist with the handling of the car, but also impact the temperatures that the tire builds up. When you stare at a dirt tire it seems that the grooves are there for traction, which is true. But the grooves that the manufacturer puts into the tire also allow the tire to release temperature build-up more quickly.
Hoosier tires have been the...
Hoosier tires have been the go-to tire for Dirt Late Model racers for quite some time. They are able to withstand the extreme conditions that the tires experience as the driver slides through the corners. Photo by John Pyle
Tire compounds also come into play. When you first look at a list of tires, it can be overwhelming. Tire manufacturers produce different types of compounds that work for different track conditions. The softer compounds are perfect for a wet or muddy track because the track will help cool the tire and allow you to run the softer tire. However, when the track starts to dry out, the team will have to stay on top of the track changes and change compounds as necessary. When the track is dry and gets a glazed look to it, you should be running a very hard tire. Because the track has a lack of moisture in it, it will heat up the tires quicker.
To help with the build-up of heat, racers have the option of cutting more grooves or sipes into the tires. Grooves and sipes are very similar in that they both are cut into the rubber that is on the tire. However, they vary greatly in the way they are cut. Grooves and sipes can be applied to the same tire, and more times than not, the deciding factor is what is required for a competitive run at your local track.
This is a Hoosier Race tire...
This is a Hoosier Race tire that hasn't been touched by grooving or siping. Notice the angle put into the tire. This would definitely be a tire to run on the front of the car for added side-bite. Photo by Jeff Huneycutt
Cutting a groove requires a special u-shaped blade that is heated and cut into the tire. Grooves can be cut a number of different ways. They can be cut at an angle, for example, which will add side-bite and increased traction. Most of the time, rear tires are grooved with a line perpendicular to the ground. This not only provides better traction, but it also helps the tire sling the mud or dirt off before that particular part of the tire travels back to the ground. But you can also cut grooves in angles that will give you more side-bite as the car is sliding through the corner.
Hoosier Tire Company is the leader in the dirt racing world. The company has won numerous championships in not only Late Model competition but also in Modifieds, Sprint Cars, and World of Outlaws. On the company's website, hoosiertire.com, there is a dirt track guide for grooving tires. If you are having trouble understanding when you should groove a tire or when not to, the Hoosier site makes perfect sense of it. The site warns that a groove or sipe accelerates wear. According to Hoosier, the key "is to balance the benefit of grooving with the increased wear. 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."
Grooving creates edges in the tire and edges create better traction.