A 4-bar dirt Late Model rear suspension is designed to have a large range of rear steer. T
Rear steer in a circle track race car is a condition caused by suspension movement. Under the right conditions, rear steer can be beneficial and enhance performance. Under the wrong conditions, it can ruin your handling.
We do not necessarily need to know the exact amounts of rear steer our cars are subjected to, but we do need to have a solid understanding of what produces rear steer and what effect rear steer has on the handling in our cars.
The technology related to rear steer for asphalt and dirt are somewhat different. There are a few similarities, but many differences in how we evaluate and use rear steer for each group. Since we cannot lump them together, we will analyze them separately.
With the rear end pointed to the left of centerline, the steering will cause the rear of t
The first element to understand about rear steer is that it is caused by rear suspension movement. As the rear corners of the car move, along with the controlling arms that locate the rear-end fore and aft, each side can move the wheel on that side forward or to the rear. Obviously, if both of the wheels did not move, or moved in the same direction by the same amount, we would have zero rear steer. When one wheel moves more than the other, we have a certain amount of rear steer.
Rear steer can either tighten a car or make it very loose. Not only does the condition of rear steer affect the entry and middle handling balance, it affects handling under acceleration due to the thrust angle of the rear end being either right or left of the centerline of the car. In dirt racing, it may be advantageous to incorporate a large amount of rear steer under certain conditions.
With the rear end pointed to the right of centerline, the car will be freed up going in, t
Tuning With Rear Steer
To see if rear steer is an important tuning tool, we turned to some experts. Joe Garrison of GRT Race Cars and Mark Richards of Rocket Chassis both said having rear steer capability in a dirt car was critical. "Rear steer helps the driver get the rear end around on dry, slick tracks without having to break the rear tires loose," said Garrison. Richards added that "if the driver has to countersteer the car a lot, you need more rear steer."
Keith Masters of MasterSbilt Race Car Chassis said, "The reason chassis builders build 4-bar cars is because of rear steer. The entry is more important to design for than the exit as far as rear steer is concerned." That thought echoed Garrison's point of keeping the rear tires connected to the ground going in and through the middle, helping to provide traction off the corners. A smooth entry provides a faster exit.
The 3-link rear suspension system can produce rear steer in both directions. As the chassi
We also talked with Sandy Goddard of Warrior Race Cars and he said his group of racers work with rear steer less than some other dirt teams, although he feels that using a degree of rear steer is very important at times. "Rear steer definitely helps get into the corners on dry, slick tracks," Goddard said, "but you can put too much rear steer into the rear suspension. A lot of guys take that to extremes."
C.J. Rayburn of Rayburn Race Cars, a driver as well as a car builder, echoed much of what the other buiders had to say. "We have always wanted rear steer," he said. "Rear steer is important in any design of dirt car." Rayburn builds the swing-arm type of rear suspension. Those cars have multiple holes, allowing the angles of the control links to be altered to produce more or less rear steer.
A rear end steered to the left of centerline will cause the thrust angle to be left of centerline and make the car tighter on entry and tighter on exit under acceleration. A rear end that is steered to the right of centerline causes the thrust angle to be pointed to the right of centerline and makes the car loose on entry and loose on exit under acceleration. Knowing these basics, we need to look at each type of racing to see how rear steer affects each type of car and how we might improve our performance using rear steer.