What is a Leaf Spring?

A leaf spring is one of the earliest and most simple forms of spring within the automobile and motorsport world. It is simply a length of an iron or steel blade, attached to the chassis and each end and tied to the axle in the centre.

They are usually stacked with different tapered thicknesses determining the spring rate and if a higher spring rate is required, more blades are stacked on top of each other to stiffen it up.

Leaf springs are effectively extinct within motorsport but many historic and classic racing cars used the leaf spring as it pre-dates the coil spring by many years.

How does a Leaf Spring Work?

A leaf spring works by simply bending the metal blades when a force is applied. The metal will always want to return to its centre resting position and will spring back to it when the force bending it reduces.

The spring rate is measured by adding the spring rate of each individual blade together in the assembly. With each end of the leaf assembly bolted to the chassis it allows the axles to be bolted to a position along the length of the spring. The mounting position can alter the effective wheel rate of the spring as well.

Benefits And Draw Backs of a Leaf Spring

The main benefits of a leaf spring and why they are still used in the automotive world today are:

  • Cheap manufacturing costs
  • Fast and simple assembly
  • Easy and cheap maintenance
  • Determine and hold the position of the axle fore, aft and side to side with no other components required
  • Very strong spring rates are achievable for very heavy machinery

The disadvantages and main reasons why leaf springs are not used within the majority of Motorsport any more are:

  • They weigh much more than alternatives such as coil springs
  • They tend to rust and crack from debris impact and weather easily
  • They take up a lot of space on the chassis
  • Low ride heights are not achievable due to how they mount to the chassis
  • Changing spring rates is very time consuming unlike swapping out a coil spring
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