If you are a car enthusiast, you may have heard the term “preload” and “how to adjust preload” questions before. If you are unsure what it is, in this article we will be discussing what “preload” is, how to adjust it and the benefits of doing so in regards to aftermarket coilovers.
What is preload?
Preloading springs involves “compressing” the spring to reduce the level of play in the springs. The more you compress the spring, the distance the suspension has to travel will decrease. Increasing the compression of the spring will reduce the amount of travel the suspension has to travel when the suspension takes on the weight of the car. The shorter the stroke, the more likely you are to bottom out. Also, the shorter the spring length, the firmer the ride (most of the time, but not necessarily a “rule”).
How do I adjust the preload on my front coilovers (coil over spring)?
We have created a tutorial video that demonstrates the steps needed to adjust the preload for your front coilovers. You can view the video below:
How do I adjust the preload on my rear coilovers (divorced damper and spring set up)?
This is one of the most common questions that we get and also one of the most commonly mis-installed part of installing your aftermarket coilovers (video coming soon).
We’ll run down the install step by step:
- Once your old spring and shock/damper is completely out of the car, you want to install the rear spring & spring perch set up first
- Make sure that there is NO SPRING PRELOAD once the rear control arm is bolted back in the car (this is the arm that the spring sits in) – you should be able to move the spring around, but not necessarily remove it completely once the arm is bolted back up (do your best to “set the desired ride height” during this step)
- After the rear spring is installed and the rear control arm is bolted back in the car (make sure the adjustable perch is in the proper location – some are on top of the spring & others are on the bottom of the spring), bolt the upper shock/damper to the vehicle (DO NOT BOLT THE LOWER PART TO THE CAR)
- After the rear shock/damper is bolted in to the upper rear shock tower, place a jack under your rear control arm and raise the arm until there is roughly 5mm of preload on the spring – you can measure the total length of the spring to determine preload (if the unsprung length of the spring is 180mm, it should measure 175mm with 5mm of preload)
- With your jack holding the rear lower suspension in place and properly preloading your rear spring, adjust the lower portion of your coilover shaft to the necessary length so that you can thread the lower shock bolt in place without adjusting the tension on the spring (a slight adjustment may need to be made using the jack, but it should be minor)
- Once the lower shock/damper bolt is tightened, you can now remove the jack from under your suspension and the rear spring/suspension is properly preloaded
- Complete your rear coilover install
Why should I adjust the preload? What are the benefits?
One reason it is important to preload your coilovers is to reduce the likelihood of the coilover from completely unseating. You want to prevent the spring from unloading to the point where the spring becomes off centered and is unable to properly re-seat itself. Secondly, each spring is designed to operate under a certain preload, similar to how car engines are most powerful under certain RPM’s. By preloading your coilover to the manufacturer’s recommended load, the coilover will be able to operate at it’s intended specs.
The most common complaints that we hear about aftermarket coilovers is usually related to preload……or the lack thereof. We recommend that you have your ISC coilovers installed by a professional shop that is not just familiar with aftermarket parts, but also familiar with aftermarket coilovers. Believe us, your money will be well spent and you will thank us……..and your passengers will thank you!