In racing, staying in the groove means that a car can stay at or near its top speed for as long as possible. The driver won't have to slow down or waste time (and distance) trying to get into the optimal position. That may sound rather simple, but the groove can change as the race goes on.
As we mentioned earlier in this article, you can typically see the groove (or grooves) on a track because of the build up of rubber from the tires. NASCAR race cars use racing slicks. Racing slicks are a kind of tire that doesn't have ridges or grooves like a normal tire does. Instead, racing slicks are smooth on the surface that contacts the track. The racing slicks are made out of a soft rubber that gets sticky as it heats up. That sticky rubber helps the car adhere to the track; however, the tires are so soft and sticky that some of the rubber sticks to the track itself. That's what creates the black line that makes the groove visible.
Depending on the race-day weather conditions, that extra rubber on the track can either benefit or harm the drivers racing in the groove. If the race is held on a hot day and the track surface is warm, the extra rubber will quickly heat up and become sticky, giving any car in the groove extra traction -- a definite plus. Conversely, if the track is cold, that extra rubber will harden, making the groove a slippery place to be. If the groove is slippery, drivers try to avoid it by taking the next most efficient route around the track.
It's easy to see how changing weather conditions -- and changing groove conditions -- can make a driver change his race day strategy. But what happens when there's more than one racing groove to choose from? Read the next page to find out how the strategy changes when a track has two or more racing grooves.