What Does ‘Pre-Assembled Coilover’ Mean and What Must the Installer Still Do?

Whenever you shop for suspension parts, you might come across the term “pre-assembled coilover”, which stores also often seek as a complete strut assembly. Even though it sounds like a plug-and-play solution, it doesn’t mean that zero work is required. Someone has already done a specific set of jobs for you, but the rest is still for you to deal with.

This page explains what does pre assembled coilover mean, and what an installer needs to check before sending the car back onto the road. 

What Pre-Assembled Actually Refers to 

A coilover is basically a shock or strut combined with a coil spring that is mounted around it. When you build one from scratch, you start by compressing the spring, then you seat it currently on the strut, and fit the upper mount, bearing, dust boot, and bump stop. This all should be done in the right order and with the right preload.

Pre-assembled means that the manufacturer has already done this stage of the work on your behalf. The strut, spring, mount, insulator, and other related hardware arrive to you already in one bolt-in unit. There are no loose parts that you would need a spring compressor to assemble yourself. 

This is the entire explanation of the term. It explains how the component itself was built before it ever made it to the shop’s shelves. 

What Parts Come Pre-Assembled 

In the most typical pre-assembled strut or coilover unit, you will normally get:

• The strut or shock body;
• The coil spring, matched and rated for the unit; 
• The upper strut mount and bearing;
• Spring insulators and isolators;
• The dust boot and bump stop;
• In many cases, mounting hardware. 

These parts are put together and calibrated at the factory. As a result, you avoid the risk of getting an old, tired coil spring or a worn mount. These are the most common problems that often come with an otherwise brand-new strut. 

What Pre-Assembled Does Not Cover

Apart from the things that come with the package, it’s important to consider those that do not. A pre-assembled unit takes care of the strut assembly itself. At the same time, it does not take care of such things as:

• Vehicle-specific compatibility checks. It will not confirm that the unit matches your exact specifications (trim, engine, suspension setup, etc). This will have to be done manually;
• Removal of the old assembly. It will not disconnect brake lines, ABS wiring, sway bar links, and lower control arm bolts;
• Torque specs. Every strut nut, camber bolt, and mounting bolt has a manufacturer torque value that must be respected; 
• Alignment. Whenever you swap struts, it changes ride height and geometry slightly, which almost always affects camber and toe; 
• Corner-specific fitment. If either left or right unit is installed on the wrong side, it can significantly affect handling and wear; 
• Final inspection. The final checks before test-driving are also not done on your behalf. 

In short terms, the assembly is done for you, but not the installation. Those are two different jobs. 

What the Installer Still Needs to Do 

There is still some job left to do after the pre-assembled coilover arrives. The main steps in the algorithm include:

1. Confirming fitment before removal. Matching the part number to the vehicle’s year, make, model, and trim.
2. Supporting the vehicle properly. Installing jack stands, wheel chocks, and disconnecting the battery where required. 
3. Disconnecting and labeling everything attached to the old strut. These include brake lines, sensor wiring, and sway bar end links. 
4. Torquing to spec. The installer has to tighten the strut-to-knuckle bolts, upper mount nuts, and any camber adjustment bolts to the manufacturer’s exact torque.
5. Reconnecting and bleeding as needed. If brake lines were disturbed, the brake system may need bleeding before the car is safe to drive.

Once all the previous steps are done, the installer will have to get an alignment of all the parts right. This is the step that is most often skipped. 

Final Word

A pre-assembled coilover is a component. It means that the spring, mount, and strut have already been matched and put together correctly at the factory. Even though a part of the work is done for you, it doesn’t mean you won’t have to deal with the correct removal, torque, corner-specific fitment, and a post-install alignment. 

Pre-assembly handling does around 20% of the traditional strut job, which is also the hardest. The remaining 80% still depends on the installer and whether they can do their part of the job properly.