For example Toyota Tacoma’s and 4Runners generally run 2″ of preload in the front. Some vehicle specific applications do have different preload requirements. If you’re purchasing springs from us we also check other factors to make sure you have the ideal spring rate. When you have too much preload the springs can’t do their part.įor most applications 1″ of preload in the front, and 2″ of preload in the rear is a good starting point. We look at suspension as a complete package and every piece of it has a purpose and it all needs to work together. When this happens we have to compensate with shock valving and sometimes that can lead to harshness. Springs work in both extension and compression so too much preload makes the springs too soft on compression. The concept that “Springs Just Hold The Vehicle Up” has some merit on long travel setups but is not true for short travel and mid travel setups. So as you can see accurate spring preload becomes much more important on shorter travel setups. While a more standard vehicle will see a 167% change in spring force for equivalent change in preload. As seen on the graph below, a long travel desert truck going from 0″ of preload to 3″ of preload only results in an 8% increase in spring force at 5″ of droop. A shorter travel vehicle with 6″ of droop will see a much larger change in spring force from an equivalent change in preload.
For suspensions with 15+” of droop the springs are already very soft and changing preload has very little impact on spring force. “Springs Just Hold The Vehicle Up” is a common saying stemming back to long travel off-road race trucks. Why Do People Say: “Springs Just Hold The Vehicle Up”:
Under articulation the spring preload increases tire contract pressure improving traction. On big bumps at speed the spring preload pushes the tires down to better follow the terrain and make a smoother, more controlled ride. Spring preload pushes the tire down and makes the suspension work. The only time spring length can affect preload is if there aren’t enough threads on the shock to get the desired preload, or if the springs will go to coil bind.Įveryone thinks about what happens when springs compress, but it’s also important to think about what happens when they extend.
The result is the same amount of ride height. Because spring rates are the same each spring will collapse the same amount under the weight of the vehicle.
In both cases you’ve applied 100 lb of force before the vehicle weight collapses the spring. An 18″ long, 100 lb/in spring with 1″ of preload will give you the same ride height as a 10″ long, 100 lb/in spring with 1″ of preload. Preload is independent of spring free length.
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