Grooving and Siping

Altering tires by grooving and siping can maximize the amount of traction and enhance the performance of the tire. However, how to prepare a tire is dependent on many variables, including track conditions and how the track will change throughout the night. Obviously, a heavy track will behave far different than a black, slick track. Therefore there is no one “proper” way to prepare a tire that will work in all conditions, so this article is just attempting to give you the basics on grooving and siping and what each technique does.

The purpose of grooving a tire is to remove rubber and allow it to run cooler, and to possibly enhance grip. Grooving a tire does two things; first it creates sharp edges for grip and more resistance against the car sliding or spinning the tires. Second, it helps sling dirt off the contact patch of the tire by helping the tire clean itself off before it rotates back around and makes contact with the track. There are many different ways to groove a tire but just starting out with the basics can help tremendously. Rear tires transfer the torque to drive the car, so when grooving rear tires the grooves should be cut perpendicular to the rotation of the tire. This will promote forward bite and help the tire “dig” into the track. Grooving front tires will allow for more steer in the car, which will help the car turn with less resistance. You can achieve this by making grooves in the tire that run parallel to the direction of rotation. This helps the tire dig into the racetrack (side bite) as the driver turns their car right or left. Grooving also helps reduce heat in the tire. It allows heat to escape from the block, or the rib, of the tire as the air flows across the tire surface.

Unlike grooving, that helps cool the tire, siping is done to build heat in the tire. In a nutshell siping is the act of razor blades cutting tiny slits into the tire. As the tire rotates and makes contact with the track the inside of the sipes will rub against each other and generate heat. The sipes will also allow the tread block, or rib, to flex more which also generates more heat. This will allow the tire to heat quicker in fewer laps which will allow the tire to grip faster. Unlike grooving, siping a tire only puts a slit in the tire and doesn’t actually take away any rubber. Caution must be used in siping or grooving since cutting the tread too deep can cause the blocks to rip or tear which will cause traction loss.

While grooving and siping can help the performance of the tire, keep in mind that altering a tire will actually increase the wear rate of the tire. Too many cuts can compromise the tread and damage the tire. There is always a trade-off when cutting a tire. Each racer should calculate what they wish to accomplish. If getting the tire to “fire quickly” is the goal, then siping is an option. However, if the track is taking rubber and is black slick, the track will get very abrasive and the tire can overheat late in the run, and cause it to give up and not repeat. If the goal is to be fast late in the run, then minimal siping may be the best option on softer compounds, since the tire will run cooler than the same tire with more siping. In this situation it may be better to use a harder compound and more siping to get the tire to heat up later in the run but won’t give up like a softer compound tire. Again, each track scenario is different depending on the track conditions encountered. Since there is not just one correct way to groove or sipe your tires, the best way is to experiment to find out what works best for you. Every driver is different, therefore every driver will groove and sipe their tires differently.