Part 1 of our education programme. Myths around coil spring preload

Part 1 of our education programme. Myths around coil spring preload

After working with Outback Armour as one of their Suspension Design Engineers for nearly a decade and having spent a total of three decades immersed in the suspension industry, I've encountered my fair share of myths and misunderstandings surrounding coil spring preload. It's an area where misinformation can lead to misguided adjustments and suboptimal performance. Let's delve into one of the most common misconceptions I've observed over the years and set the record straight on coil spring preload.

Preload Increases Spring Rate

There's a common belief that increasing preload automatically boosts the spring rate, making the suspension stiffer. Spring rate primarily depends on the design and material of the spring itself. This can not be altered with preload. Excessive preload can indeed stiffen the suspension but this is due to other changes that are happening in the suspension such as changing the roll centre.

The height of a spring at normal ride height is governed by the weight that's applied to it. By repositioning the spring seat to a different position, (eg winding up the seat on a coilover strut) does not alter the height of the spring because the weight applied to the spring at ride height has not changed. This only changes the ride height of the vehicle.

There are disadvantages to excessively increasing coil spring preload. One of them is coil binding (going to solid) before the suspension makes contact with the bump stops. This happens if the distance between the upper and lower mounting positions for the coil spring is greater than the distance to the bump stop while also taking motion ratio into consideration.

MCA has a good video on this topic.


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