I've just returned from a vacation that I think many of you would find enlightening — several races on the “World of Outlaws” sprint car racing circuit. I picked the races held in Rossburg, Ohio (Eldora Speedway) and Knoxville, Iowa (Knoxville Raceway), considered by many fans to be the premier races on the circuit. Although the closest hotel I could find for the Eldora race was 34 miles from the track, the experience was worth every mile of the drive.
Think of the World of Outlaw vehicles as simple, yet highly evolved chassis design cars with Nascar Winston Cup horsepower and half the weight. They're very fast — scary, in fact — and almost never travel straight ahead. The Circuit bills itself as the “Greatest Show on Dirt” since most of the tracks are unpaved ovals ranging from a quarter- to a half-mile long, raced counterclockwise.
The oval is negotiated by steering the car sharply left as the straight track section ends, then applying rear wheel power to cause all-wheel drift (oversteer) through the end turns, preparing for slingshot acceleration to speeds of 130 mph or higher down the opposite straight section. Much passing and jockeying for track position occurs during the all-wheel drift sections, while the cars are actually steered to the right as they turn left, giving new meaning to the notion of trusting your neighbor.
Since the track surface is constantly changing, chassis tuning and tires are two variables that often determine the winners. The torsion bars are screw-jacked to load each corner of the car for maximum track bite and desired driver “feel.” Tire inflation is tailored to track conditions, as well as the driver's preference for a loose or tight feel.
Individual tire selection setups are works of art: three, if not all four, corners use different tires; tire brands can differ across an axle; and right rear tires are several inches taller than left rears. The resulting tire stagger, coupled with a locked rear axle, creates a strong left turn preference that, when properly matched to track length, banking and speed, powers the car around the oval with uncanny precision — even though it appears to be only marginally under control.
Some crews use special tire carving irons to alter tire tread designs in search of more “bite” under certain track conditions. Most rear tires are also designed to give a calibrated increase in diameter when spun up to high speeds for incremental track speed or a “poor man's gear change,” while still retaining the high acceleration available from a shorter gear as the car enters the straight track sections.
Braking traction is nearly irrelevant, since these are “go” cars, not “slow and go” cars. In fact, if all is well and traffic permits, the cars appear to run flat out around nearly the entire oval. When the air is cool and damp — prime conditions for the methanol injection system — the suspension setup is right, the dirt is packed but not polished, and the tires are broken in but not used up, the sprint car symphony is a rare experience.
As I watched the crews working on their cars almost continuously in hotel parking lots and then later in the pit areas, I was impressed by the amount of attention they gave to tires. Some kept their best tires covered to hide individual carved pattern designs from unwanted eyes. Others used calibrated gauges to set inflations within a fraction of a PSI. They were all looking for that little detail that might provide the edge needed to win.
While these highly specialized tires and the jobs they're designed to do are very different from their trucking counterparts, the importance of their performance to overall success is similar. If you're not convinced, visit www.worldofoutlawsracing.com and schedule a trip.