Suspension Glossary

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Suspension Glossary

Post by Amskeptic » Sat Jan 14, 2012 10:57 am

********** Suspension **********

Toe - wheels are not exactly parallel, toe-in is if they want to roll towards each other, toe-out if away from each other. Front axle prefers toe-in, rear prefers toe-out

Camber - wheels are not exactly vertical, if they lean in at the top camber is negative, if they lean out at the top camber is positive

*Caster- the centerline of the wheels is slightly behind the centerline of the steering axis at the ball joints > this helps car roll and return to straight

*Steering Axis Inclination - helps dial in dynamic response and centering action > a steering axis that is inside of the tire footprint will tell driver of braking loads by jerking wheel towards side of greatest traction (positive scrub radius), negative scrub radius will actually try to help car self-correct in uneven braking traction events

*Ackerman Effect - front wheels describe two different size circles in corner, angle of steering arms will make inside wheel turn sharper to hold the smaller inner circle > if outside is 20*, inside needs to be 23*
*non-adjustable parameters

Ball Joints - allow steering and suspension movement between the supporting arms and the steering knuckle/wheel assembly > early VW used horizontal link pins at arms and vertical king pins for steering axis ... we like our ball joints

Tie Rods - transmit your intentions from the steering box or relay lever to the wheels using baby ball joints at the ends for flexibility

Drag Link - sort of like a "main tie rod" from steering box to relay lever on buses, it has baby ball joints too

Pitman Arm- is the stout push/pull lever coming out of the steering box

Relay Lever (swing lever) - in buses, transfers the fore/aft push/pull of the drag link to side-to-side action of the tie rods and wheels

Four Wheel Alignment - the superior method of getting all of your wheels cooperating with each other as to where they all want to go

Spring Plate - the thin wide plate arms that go from the rear wheel assemblies to the torsion bars which spring the car, they also transfer all acceleration and braking forces

Diagonal Arm - introduced with the half-shaft rear axles, they transfer cornering forces to the rear torsion tubes > older VWs swing axles used to transfer cornering forces directly to the side plates of the transaxle

Spring Plate Bushings - allow the torsion bar/spring plates to pivot in nice quiet isolating rubber
Torsion Bar Splines - allow you to adjust the ride height of the car by indexing the torsion bar to the spring plate
Sag - a typical result of torsion bar settling > it usually takes only once to re-adjust suspension back to factory height

Play - a description of what happens when closely fitted parts no longer do

Zerk Fitting - a spring-loaded ball in a nipple that allows the introduction of grease into suspension components without it subsequently leaking out

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