Have you ever wondered why the steering wheel re-centers itself without your input? Contrary to what you might think, there’s no complex mechanism behind the wheel’s return to the center position. Instead, it relies on a steering angle called the caster angle. If the steering wheel doesn’t return to the center automatically, your vehicle might have a serious issue.
How Does a Steering Wheel Return to the Center?
Two factors work together to ensure that the steering wheel will automatically return to the center position. One is the caster angle, and the other is self-aligning torque. Let’s take a look at both factors to see how they work together.
What Is the Caster Angle?
Sometimes shortened to caster or spelled as castor, the caster angle is the angle formed by the vertical line that represents the steering axis and a horizontal line set by the steered wheel. It’s one of the wheel alignment angles, the others being the camber angle and the toe angle.
You can get a better idea of the caster angle by observing your vehicle from the side. Envision a vertical line that passes through the front wheel’s center. That line is the steering axis.
Now, imagine another line that follows the suspension components attached to the center of the front wheel. The angle formed by that line and the steering axis is the caster angle.
If the caster angle slopes toward the vehicle’s back, it’s considered a positive caster angle. Conversely, if the angle slopes toward the front end, it’s a negative caster angle.
The caster angle moves the wheel’s rotation forward with respect to the road surface. It ensures that the front wheels’ pivot point is slightly angled backward instead of pointing directly perpendicular to the ground.
The angle doesn’t alter the part of the tire in contact with the road surface. Instead, it moves the pivot point ahead of the contact spot between the tire and the ground. Centripetal force (the force that makes an object follow a circular path) returns the tire and wheel to a straight position, and the steering wheel moves back to the center.
Because of the dynamics of the caster angle, when you turn the wheels all the way in one direction or the other, it raises the front of the vehicle slightly.
The center of the steering is the place where the bumper height is the lowest, so because of caster angles raising the front of the vehicle against gravity, the wheels naturally want to return to center because that’s the lowest spot and it’s where they like to rest, even if the vehicle is moving. This varies a bit from vehicle to vehicle but you can get a tape measure and demonstrate this change when the wheels are turned sitting still.
The center of the steering is the place where the bumper height is the lowest, so because of caster angles raising the front of the vehicle against gravity, the wheels naturally want to return to center because that’s the lowest spot and it’s where they like to rest, even if the vehicle is moving. This varies a bit from vehicle to vehicle but you can get a tape measure and demonstrate this change when the wheels are turned sitting still.
–Richard McCuistian, ASE Certified Master Automobile Technician
Self-Aligning Torque
Self-aligning torque is the torque generated by the spinning tire while turning around a corner. Torque is a force that makes the object rotate around an axis. In the steering system, self-aligning torque steers the wheels around the vertical axis that leads to the steering column.
Also called aligning torque, self-aligning torque is created by slip angles. These angles are the differences between the angles formed by the tire that touches the road surface and the angle of the wheel’s direction. If there is a slip angle, the self-aligning torque generally steers the tire toward the direction that the vehicle is going.
Self-aligning torque isn’t the only force that affects the steering wheel. For example, the pneumatic trail is an axis of movement in the tire that helps center the wheel and the steering wheel. However, self-aligning torque affects the tires and steering system more than the other types of force.
What If the Steering Wheel Doesn’t Return to Center?
The caster angle, self-aligning torque, and other forces work together to return the steering wheel to its neutral position. But what if the wheel doesn’t return?
Let’s look at the possible issues caused by a steering wheel that doesn’t return to the center position:
Stability
The steering wheel contributes to your vehicle’s stability. If it fails to return to the center position, it can make your car or truck vibrate. You may also crash if you don’t force the steering wheel to return to center, which can be extremely inconvenient if you have to do it on every turn.
Safety
You can compensate for steering wheel issues by manually turning the steering control part. However, it adds to your workload as a driver. You’ll get tired faster and might become distracted.
Possible Reasons For Steering Wheel Failure
What causes the steering wheel to stop returning to the center position? And can we do anything about these problems?
Improperly Adjusted Steering Gear
In many cases, the steering wheel doesn’t return to the center position because the steering gear was incorrectly adjusted or tightened. The steering system can develop issues like excessive play in the steering wheel. Technicians fix these issues by adjusting the steering gear, but they might make mistakes during the repair process. For example, if they tighten the steering sector too much, the sector shaft puts too much pressure on the worm gear.
Stuck Parts
Steering parts can bind to each other or get stuck. A stuck part can stop the steering wheel from centering after completing a turn.
Some of the steering parts that might prevent the steering wheel from returning to the center if they get stuck are the following:
- Ball joint
- Bell crank
- King pin
- Steering column
Misaligned Wheels
Wheel alignment affects the steering wheel’s ability to return to the center position. The wheels must align with the suspension to ensure stability. However, the wheels eventually lose alignment, which can lead to stability issues if left unattended. Since the wheels are connected to the steering wheel, misalignment in the former will affect the latter.
Fortunately, you can fix this problem with a wheel alignment service. Realigning the wheels should correct the steering wheel’s alignment.
Incorrect Caster Angle
The caster angle might have changed at some point. A collision or accident can jolt the steering parts out of alignment, changing the caster. Alternatively, installing and adjusting parts in the wrong way can change the angle. The steering system will need realignment to correct the angle.
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