One step down from the slushy track is the heavy track, where the tires send chunks of soil flying through the air. These chunks of mud, up to 3/4-inch in diameter have the consistency of soft modeling clay. While most of the traction still comes from the shearing of the soil (aka tire digging into the surface), some begin to come from the surface of the tire itself. To gain maximum performance you’ll want anywhere from 40 to 50 percent of your tires grooved.
A tacky track is characterized by stringy shaped chunks of soil whose consistency resembles stiff or hard modeling clay. Traction on tacky tracks comes approximately 50 percent from shearing of the soil and 50 percent from the tires. Therefore, Furney says you’ll want approximately 30 to 40 percent grooving.
Not surprisingly Furney’s definition of a shiny track is one that shines under the lights, largely due to the moisture content of the clay. These tracks tend to be very smooth and very slick. The surface wetness of the track makes it very difficult to gain good traction. Furney says you need up to 60 percent grooving on a track like this.
The dry-hard condition is also called black slick, getting that name from the visible black rubber coating that develops on the surface as the tire wear deposits increase as the race wears on. Depending upon atmospheric conditions, dry-hard tracks can be just a handful of laps away from going dry slick. Sticky tires are the rule for a dry hard/black slick track. Do not go anymore than 15 percent grooving, siping will also help on this track surface.
Ah dry slick, characterized by the cloud of dust that develops behind the cars, all of your traction on a dry slick surface comes from the tire contacting the track. For these conditions you’ll want somewhere in the neighborhood of 15 to 30 percent grooving plus a good deal of siping.
We haven’t been to too many dirt tracks where the surface stays exactly the same from hot laps until the white flag of the feature. That’s part of the beauty of dirt track racing. Since surfaces change, how you choose to prep your tires for the evening’s action will have a tremendous impact on how well you do. Often times, a track that starts out tacky ends up dry slick. If you’ve got heavily grooved and siped tires for a tacky race make sure you have another set of tires prepped with less grooves and more sipes for the feature when that track slicks over.
In addition, other factors can contribute to changes in the tracks surface. Take East Bay Raceway Park for example. Given its close proximity to Tampa Bay, a tidal body of water, East Bay’s racing surface changes with the tide. When the tide is in, the track tends to be more tacky and stays that way throughout the evening of racing. When the tide is out, dry slick is the rule.
Tracks in other low lying areas can experience the same phenomenon. East Bay track manager Todd Hutto told an interesting story about when the winged limited sprints come to the track. Even with the tide in, the track will go black slick. Hutto suspects that the extra downforce created by the wings cause additional rubber to be literally driven into the track forming a barrier that prevents water from reaching the surface.
“You can go out to the track after the Limited Sprints run and take a knife and cut a hole in the track and watch the water come up to the surface, yet the area around the hole will be blacked over and dry,” says Hutto.
Not only does that theory stand to reason but it brings up an excellent point. The division or class running in front of you has a lot to do with how the track will act when you go out. So keep an eye out for the order of the classes in addition to everything else.