Inverted Shocks and what you should know..
Inverted shocks require a basic routine service!
Don't let that scare you, but we just want to be clear about it. Inverted shocks differ from a standard upright in design which makes them much stronger. Because the entire assembly is larger and the piston rod is housed inside of the threaded base, your inverted shock can take a lot more abuse, and because the "guts" of the shock are moved away from the hub, the inverted shock runs cooler - which means it performs at peak for much longer.
The downside of an inverted shock is a clunk noise that can develop over time. To explain this as simply as possible, inside the threaded housing (the lower half of the assembly) are a series of alignment shims (it keeps the shock insert centered). To keep everything sliding smoothly, there is grease applied to those guide shims. As we live on earth, we deal with gravity, and that force causes the grease to slide down and away from the shims.
This is exacerbated by the fact that no strut assembly is perfectly straight up and down, there is a bit of caster (forward/ rearward lean) on each strut. This means that the shock when moving up and down into the housing is not a directly straight line. There is an edge that gets favored. That edge is where the grease wears first and that's when the clunk starts. Here's a visual explanation (OEM Subaru STI Pinks shown for reference, but exact same concept/ explanation):
So the clunk you hear is the shock going in at a fraction of a degree, and striking the dry shim. The grease not only keeps it lubricated, but also acts as a bushing, in simplest terms. When there's no grease, the "bushing" is gone.
It doesn't matter if you have an $11,000 rally suspension, or OEM Subaru STI pinks; they need service. It's not exclusive to certain brands; and if they say otherwise, they are uniformed of how an inverted shock works. You have two metal pieces sliding in-between each other with grease in between - grease isn't a forever item. It has to be reapplied.
So, how do you service inverted shocks? It's easy and there's actually a ton of videos on youtube, but here's a written step by step (search "inverted shock clunk" on youtube if you want to see videos)..
- Remove the assembly from the car
- Remove any preload from the spring
- On the bottom, remove the blue adjustment cap to expose the 19mm nut
- Heat the 19mm nut with a small torch and remove the nut with a few quick bursts with an impact (do not let the nut spin to oblivion)
- Pull the insert from the housing
- Apply a heavy coat of grease inside the threaded housing coating the brass bearings as much as possible. *CV Axle grease works well
- Apply a thin coat of grease to the insert body
- Carefully place the shock insert back into the housing
- Reinstall the 19mm nut
- Reinstall the blue knob cap
- Reinstall on the car
*To help prolong this service, routinely apply a coating of grease where the insert goes into the housing, and about 3-4" up. You do not need to take anything apart to do this. Just apply some grease to your finger tips, and rub it around the insert body making sure to get an even coat all around.
As I said, this is a very common service for inverted shocks. The benefit of an inverted shock far outweighs an upright shock in every way, even factoring this service. Once the assembly is off the car, this is a 15 minute task per shock.
If you want to take advantage of our 3 year warranty, we will provide this service at no charge during the warranty period. You just have to send them in.
This service should be performed soon after the noise starts to develop. If it gets bad enough, the inner shim can shift out of position and do further damage to the inverted housing and insert.
*Be advised that increasing caster angle during your alignment will create more angle on the inverted body and could increase the interval times on servicing.*