For corrections see our page on oversteer/understeer corrections.
Understeer has several common names such as plow, push or tight. Whatever word you use, it describes a condition where the car is not turning "sharp" enough. From the driver's seat, this may appear as the car not pointing where you want it to go, and often towards a fixed object like the wall.
MEASURING TAPE
A great little tool for diagnosing such handling
problems is a piece of white tape on the steering wheel. This tool has been used
on race cars for over 30 years now, but is very helpful once you know how it is
used.
Look at the
tape on the top of the wheel..this is only a reference. The tape may look
different, depending upon your steering wheels placement for racing.
The diagnostic procedure is to drive through corners slowly, as on a warm-up lap, and note the position of the tape on the steering wheel. Use this position as a base steering angle or reference angle. Next, with your car at racing speed, go through the corners and note the new position of the tape on the steering wheel.
Technically, if the angle is larger at racing speed, then the car is considered to be understeering. In some cases you can turn the steering wheel more (or even all the way to the locks) and the nose of the car still doesn't go where you want it to go. Obviously, the car is pushing in this case, but with the tape you can measure the amount of understeer.
If you are going around the corner and the nose of your car is pointing to the wall, note how much of an angle it is at, on the next pass back off the throttle a little earlier and just as you set the car into the corner give it a kick in the pants for a second and see what the nose does in the same spot. Will the car nose move down and the rear come around. if it does, you can back pedal your way around the turn and have enough grip with the tire force to cause minor slip angles with the rear end. as long as you can keep the cars nose pointed the way you want, you will gain opposite lock in the turns.
TIRE FORCES
If you are experiencing excessively large steering
angles in the middle of a corner, and must wait until later in the turn to apply
the throttle, then tire forces are worthy of consideration.
Often this problem can be reduced (or eliminated) by increasing the cornering force generated by the front tires. While this sounds simple, accomplishing this goal often eludes many racers (even some pros). Many factors such as temperature, compound, et c., impact the cornering force a tire can generate.
Front tire cornering forces are also impacted by the dynamic camber (or absolute camber) angle. With improper dynamic camber, you could very easily be loosing several hundred pounds of cornering force. This force could have been used to go faster, too! For example, we were working with a stock car at Accord Speedway and by optimizing the camber we improved the lap times by slightly over 1.5 seconds.
DYNAMIC CAMBER
A reduction of cornering force is not necessarily
because you have the wrong static camber. It's because the dynamic camber is not
optimal.
It is important to understand that static and dynamic cambers typically are not the same. As your car travels through a corner, the body leans. This causes the camber to be different on the race track than it is back in the garage (static). This is true for any car that has independent suspension such as the A-frames on the front of a stock car (weather it's a GM or Ford style), modified, or dwarf car.
CAMBER & SUSPENSION
When the car's body leans in a corner, the
outside suspension compresses and the inside suspension extends. In other words,
the outside suspension moves in the bumper direction and the inside suspension
moves in the rebound direction.
If your suspension has no camber change, as with the old VW suspension used on the front of dune buggies, then the wheels stay parallel to the body. If the body leans 5 degrees, then the wheels also lean five degrees. Unfortunately, the tops of the wheels lean in the wrong direction. This is why camber change (a.k.a. camber gain) is so important.
To illustrate this, imagine you were looking at the right front suspension of a car making a left-hand turn. In this turn, the car's body leans five degrees toward the outside of the corner. At the same time, the right front suspension has compressed 2 inches from its normal position. Say that back at the garage you placed a camber gauge on the right front wheel. You then move the wheel 2 inches in the compression direction. Now, when you check the camber gauge you find the camber has changed five de grees in the negative direction.
In this example, even though the body has leaned fives degrees, the wheel has tilted back five degrees and the dynamic camber for this example remains the same as the static camber. In reality, unless you set up your car to achieve a specific camber curve , chances are your dynamic camber will be very different from your initial static camber.
The best thing to do is simulate your caster camber gains and losses in the garage. We explain this in the caster camber section.
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