Part 1: Setting Up And Maintaining Coilover Shocks
Do you own a set of coilovers yet? Why not? Your neighbor just sold off two kids to get a set for his Chevy LUV. Why don't you step up? Do you think they're not important enough to your suspension? Do you think they're too complicated? You'd be wrong on both counts if you did. They're probably one of the most versatile components you can add to your suspension, and really not all that expensive when you think about it. They give you the option of changing valving stiffness, spring rate, and even ride height, and it can be done after they're already purchased. You can break down the damping and ride qualities and abilities into different replaceable components with coilover shocks, giving you the ultimate in owner-adjustability. No other suspension component does this so well and at such a sensible price.
We felt confident enough to maintain and set up up our own coilovers after taking a little time to sit down with Bilstein's Joel Ward and Shane Casad to take a look at how a typical coilover shock (in this a case a 9100 Rock Crawler with digressive valving) can be modified and maintained to perform the way we wanted. And luckily we snuck in a camera as well so we could show you how to become an unauthorized pro at working on your own coilovers. Mind you, we're demonstrating on a set of Bilsteins, and this might not be the shock you have, but most steps are either the same or very similar, so use this as a general guide.
By the way, any type of valving and spring-rate generalities we make go right out the door once you turn your shock more than 10 degrees sideways. For shocks turned at an angle, valving and spring rate will have to be much stiffer.
This month we only have enough room to show you the routines for shock maintenance and setup of a coilover on your ride. Next month we'll cover the coil setup rituals you can use to dial in on your own truck.
Before we delve into this, we should probably explain how a standard coilover remote-reservoir shock dampens. This is not an external or internal bypass shock we're talking about, just a standard remote-reservoir shock that controls compression and rebound via the valving (mostly).
First of all, the shock is pressurized with nitrogen. The nitrogen does not mix with the oil in the shock, but instead holds pressure on a dividing piston inside the reservoir, which in turn puts pressure on the fluid in the shock to keep it from cavitating. The shaft of the shock travels up and down inside the body of the shock, with a valve stack and piston on the end of the shaft that controls how fast or slow the shaft travels into or out of the body of the shock.
Whether you're changing the valving or rebuilding the shock, you're going to have to know how to tear it apart and put it back together. Most of the steps can be done with a rubber mallet, a torque wrench, a couple of Allen wrenches, a towel, a pick, snap ring pliers, and a gallon of oil. We're working on a Bilstein Rock Crawler shock, but this should be pretty much standard teardown for all coilover shocks.
To disassemble the shock, start by unthreading the coil retainer ring and removing the coil equipment. Release the nitrogen via the Schrader valve on the reservoir, and place the shock in a soft-mouth vice, holding it by its cap (upside down). Incidentally, this top cap should never have to come off the shock tube, and if it does for any reason, then it should probably not be done by you.
On our Bilstein coilover, three Allen screws hold the shock together. Once these are pulled, the wiper (lower) cap will come off the body. A rod guide is in the bottom of the shock's body doing exactly as its name implies. The rod guide is held in by a snap ring that needs to be removed. Using either the special shock-rod guide hammer (which we're sure few of you own) or by finding another way to do it, gently tap down on only the rod guide to make room to get the snap ring off, taking care not to pound on or near the shaft or its bushings, nor on the body tube of the shock. Once the snap ring is removed, slowly and gently slide out the shaft, rod guide, and valve stack. With any luck, you won't displace too much oil out of the shock body and the only reason you'll need to add any is if the shock oil should be replaced (call your shock manufacturer to find who sells their shock oil or a compatible substitute).
Now that you have the shaft out of the shock's body, you can start to work on what you need to. If the shock tube or the reservoir needs replacement or maintenance, you'll have to empty the shock of its oil (into a proper oil receptacle).
The rod guide allows the shaft to slip in and out of the shock body with very little friction. The rod guide will come off after you remove the valve stack at the end, but before you slide it off the shaft, you should check for any play or wear in the bearing on the guide. If it seems a little sloppy or the seals look a bit trashed, don't hesitate to buy a rebuild kit since they're cheap and well worth the price of a well-working shock. To pull out the seals and replace them, use a dental pick (once you touch them with the pick, they're shot, so don't pull them out if you don't have extra ones).