The plates that separate each...
The plates that separate each blade shown above can be placed in different spots to widen or tighten up the space between each sipe. Photo by Rob Fisher
Here's a helpful tip on grooving from Mr. Furney. "For anything under 35 laps, the grooving iron should be adjusted to cut a U-shaped groove with the bottom of the groove no more that 1/4-inch deep or the same as the factory tread groove. For longer features of 50 laps or more, tire wear may be significant. In those cases we need to consider the condition of the track at the end of the race. Often you start tacky and end dry slick. At the green flag you need a lot more grooving than you do at the end of the race. Therefore, for a long race you need to cut a V-groove as opposed to a U-groove. As the surface of the tread wears through the race, the percentage of your grooving will decrease thereby giving you an appropriately prepped tire for a dry-slick track.
For this article Speedway Motors sent us the new state of the art patented Van Alstine G-1000 Tire Groover. This groover has an instant-on feature so that when you touch the Teflon padded head to the tire surface the blade gets hot instantly. After smoking the tires with the highest setting we backed down to a "3" to groove our Hoosier D21s. This groover made quick work of prepping six tires for an upcoming trip to Ocala Speedway, a central Florida high banked half-miler that usually goes somewhere between black slick and dry slick by nights end. Ocala runs the Late Model feature second, so the track should still have some tackiness by the time we get on. The 25-lap feature is not long enough for the V-grooves so we stuck with U-shaped ones and added some sipes.
Here's a little tip to make...
Here's a little tip to make your siping life easier. Ordinary baby powder or talcum powder makes pushing a siper through the tread a bit easier and helps to keep your cuts straighter. Photo by Vahok Hill
Speaking of tire siping, did you know that it actually has its origin in the nautical industry? It was discovered that shoes with fine cuts in the soles at right angles to the direction of travel would assist sailors in maintaining a good grip on a wet deck in high seas. While the same principal works for race tires, siping also allows the tires to heat up faster by reducing the stiffness of the tread blocks. This is particularly beneficial on dry-hard/black slick or dry-slick tracks where there tends to be a lot of cautions as the tires will come back up to temperature quicker.
A tire under static load will deflect to a certain degree. A tire under a dynamic lateral load (as in going through a corner) will deflect even more. Siping a tread block increases the deflection and in turn generates more heat, consequently softening the rubber even more, thereby creating greater traction.
Like grooving, how you sipe a tire is directly related to the track conditions. Sipes are by and large useless on wet, heavy tracks and make the most difference on a dry-slick track. They can be as close as 3/16-inch apart, but that takes a lot of skill if you don't have the right tool. Getting them too close together can lead down the path of chunking, which we will get into a little bit later. So to keep our sipes parallel we relied on the Speedway Motors Mega Siper. This siper is machined out of billet aluminum and has 14 adjustable blades. Adjusting the blades is a snap by removing just two screws on either side. We chose a pattern that only used half of the blades because we knew that Ocala would retain some of its tackiness so we didn't need as many sipes as we would have if the track went dry slick.
Note how this racer spread...
Note how this racer spread the powder evenly over the tire. Photo by Vahok Hill
Another nice feature of the Mega Siper is that you can vary the distance between each sipe by changing the number of plates in between each blade. Plus, it uses standard utility knife blades that you can buy at your local hardware store.
Grinding is significantly different from grooving or siping, but no less important. Grinding knocks off the new surface of a fresh set of tires. That allows you to immediately utilize the good rubber from the drop of the green. Since you don't have to wait for that top layer to wear off, grinding is particularly useful in short heat races where the tires don't get much wear.
Grinding is also a valuable step in prepping tires that already have some laps on them. Not only will grinding remove the outside work hardened layer of rubber from a used tire, but you can also use a grinder to smooth out inconsistencies to return it to like new status. However, grooving is probably the trickiest of the three tire prepping processes.