What’s a spindle?

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Spindles attach a wheel assembly to a vehicle and are typically made of forged steel. They rarely require maintenance but can fail due to heat or stress. Trailers use spindles instead of full-length axles for better movement. Multiple axle-mounted wheel assemblies with an air lift system can prevent spindle breakage.

A spindle is part of a vehicle’s suspension. By tying the wheel and tire to the steering system, the axle is at the front of the vehicle in most cases; however some front wheel drive vehicles also have rear spindles. The shaft rotates between the upper and lower A-frames or on the strut. The inner and outer wheel bearings mount to the axle and the retaining nut on the end secures the wheel in position. On most vehicles, the front brake caliper is also mounted on the axle.

Acting as a short axle, an axle is used to attach a wheel assembly to a vehicle. Typically made from one piece of forged steel, spindles must be extremely strong and durable to support the weight of the vehicle. While most spindles use a wheel hub to mount the wheel and tire in place, some wheels mount directly onto the spindle without the use of a hub. These wheels are known as spindle mount wheels.

Trailers and farm implements often use spindles instead of full-length solid axles. These screws are subjected to incredible loads and occasionally break. When this happens, it is rarely possible to weld the spindles in place and repair them. New spindles are used to replace broken ones and are usually changed as a complete unit. The use of spindles instead of axles in machinery allows for better articulation and movement of the tires and suspension from side to side.

Vehicle spindles rarely require specialized maintenance. Greasing the inner and outer wheel bearings and making sure a cotter pin is in place in the castle nut is usually all that is required. Most spindles fail due to heat from a dry or over-tightened wheel bearing or stress from turning a very sharp corner. When the unit is turned too sharp it causes the tires to skid and drag around the curve. This drag puts a tremendous amount of stress and load on the screws, often cracking and breaking them.

To prevent breakage, trailers often use multiple axle-mounted wheel assemblies combined with an air lift system to lift selected wheels up and off the road when making sharp turns. Once the platform has completed its turn, the label spindles are lowered back onto the road. This arrangement allows multiple wheels to evenly disperse the weight of the load to prevent damage to the spindles.

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