When involved in a collision, things tend to be knocked askew. Body bends and frames twist. A twisted frame can cause all kinds of problems, primarily with the steering. Most modern cars involve what is called unibody construction. The body is designed to act as the frame. Rear suspension components can be incorporated into the body as well, but usually the design includes framing components to mount the suspension and drive elements to the car. Most pickup designs still incorporate separated body, bed and frame. If the frame is out of alignment it will cause uneven tire wear, steering problems and mechanical parts may experience premature failure and wear. Collision repair includes checking and restoring the frame alignment. Hydraulic rams and winches are used to pull the frame into shape. Then there is steering. There are many constituent specifications that define proper steering geometry. Caster, camber and toe-in. Top Notch Body Shop & Mechanic delves more into this topic below.
Toe In Car Handling
First toe-in. If you measured the from center to center across the front of the steering tires, the front measurement is narrower than the back. This is tow-in. Mechanical steering components have play in steering joints and the tie rods and other linkages flex. Driving forward forces tend to spread the front tire leading edge out. Without toe-in these forces would push the front out and the rear in causing scuffing and wear of the front tires. A slight tow-in allows the tires to spread out to their proper alignment saving the tires and aiding steering.
Negative Camber Alignment
Camber is the tilt of the tire in or out vertically from top to bottom. Generally, a negative camber is used for those with an aggressive driving style. Negative camber indicates that the wheel tilt in at the top. Perpendicular is zero camber with a tilt of 00. Negative camber improves handling on turns, but the wheels run more on the inner edge that on the full tread reducing straight-way traction and creating a phenomenon known as camber thrust. If the wheels have traction everything is okay. But if one wheel loses traction, in wet or icy conditions the vehicle will be thrust in the direction of the wheel that has lost traction. Because of this camber can be a bit controversial.
Caster Angle Problems
Caster is the forward to backward tilt of the wheels turning parts in relation to the axle. This tilt is what allows the steering wheel to return to the neutral position. But it is set to allow drift to the outside or right. This allows the compromised or inattentive driver’s vehicle to pull to the outside of the road rather than drift into oncoming traffic, it is a safety measure and is referred to as cross-caster. If you noticed that on turning the car drops slightly into the inside of the turn as the outside rises. This aids handling, but after the turn the car wants to return to a neutral loading on both wheels, this is what pulls the wheels into a straight direction and is a result of caster. Positive caster may increase turning effort, not a problem with modern power steering, but positive caster makes the vehicle more stable as the speed increases and will increase tire lean in turns as well.
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As can be seen, not only is wheel alignment a parcel of compromise but is necessary for safe and reliable handling, just make sure it’s within the manufacturer’s specs. Of course, this depends on a straight and true frame. Most frames are factory specifications, better than many out of the factory due to construction tolerances, but a body shop must put the frame to specs, in many cases creating a better aligned frame than that from the factory floor. Not all vehicles allow fine tuning of the steering geometry’s in all aspects and therefore rely on factory frame specifications to make all things right. Top Notch Body Shop & Mechanic can handle all your auto body needs. Contact us to discuss your next project.
