STEERING & SUSPENSION

Steering system types - 1

Rack and pinion

 

Rack-and-pinion steering is the most common type of steering on cars, small trucks and SUVs.

A rack-and-pinion gear set is enclosed in a metal tube, with each end of the rack sticking out from the tube. A rod, called a tie rod or axial rod, connects to each end of the rack.

The following diagram shows how the rack-and-pinion gear set interacts with the steering wheel.

The pinion gear is attached to the steering shaft. When the steering wheel is turned, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm which is attached to the spindle.

The rack-and-pinion gear set has two purposes:

- It converts the circular motion of the steering wheel into the linear motion needed to turn the vehicle’s wheels.

- It creates a gear reduction, which makes it easier to turn the wheels.

 

Variable ratio steering

Some cars feature variable ratio steering.

This rack-and-pinion steering system has a different number of teeth per cm (tooth pitch) in the centre than it has at the ends. This makes the steering less sensitive when the steering wheel is close to its centre position. When it is turned towards lock, the wheels begin to react more quickly to steering input.

There are two types of rack-and-pinion steering systems:

- End take off, where the tie rods exit from the end of the steering rack via inner axial joints

 
 
 
- Centre take off, where the tie rod ends attach to the centre of the rack with bolts

Steering system types - 2

Recirculating ball / Steering box

 

Recirculating ball steering is the most commonly used steering system in heavy vehicles, trucks and the larger/heavier SUVs.

Parallelogram linkage:

- Pitman and Idler arm remain parallel
- System absorbs shocks and vibrations

How does the system work?

The steering wheel is fixed to the steering shaft which has a threaded rod at the end, like a bolt. When the steering wheel is rotated, it turns this rod. Instead of twisting further into the block as a conventional bolt would, the rod is fixed. Therefore, when it spins, it moves the block. The block has gear teeth cut into the outside of it. These engage a gear that moves the pitman arm.

 

 

The threads in the rod are filled with ball bearings which recirculate through the gear as it turns. The ball bearings serve two purposes:

- They reduce friction and wear in the gear.

- Without the balls in the steering gear, the teeth would momentarily come out of contact with each other when the steering wheel changes direction, making the steering feel loose.

The recirculating ball / steering box steering system has two main advantages:

- The pitman arm and idler arm are always parallel.
- The system absorbs shocks and vibrations better than the rack-and-pinion system. However, it is not as compact and is usually less responsive.

 

Please publish modules in offcanvas position.