Sealed suspension shocks, such as those made by Bilstein, typically offer predictable and reliable performance over their lifespan. Because they are not adjustable, however, these shocks are generally discarded when they age and begin to sag. By adding your own valve to each shock, you can re-pressurize them as they sag, and fine-tune the stiffness at each wheel.
Instructions
- 1
Put on the safety goggles. Secure the shock in the clamp at the base of the drill press. Bilstein shock cylinders have a slightly widened "shoulder" at the top of the outer shock body. This is the ideal location for the valve, as the broader shape gives additional clearance for the tip of the valve inside the cylinder. Position this "shoulder" below the drill bit.
2Fit the 1/8-27-inch bit to the drill and power it on. Move it very carefully down to the edge of the shock and apply very light pressure. When the wall of the shock is breached, it will depressurize quite suddenly. This will possibly force out some of the metal shavings from the drilling, so be sure your eyes are fully covered by the goggles
3Fit the machine tap to the drill and push it through the drilled hole, forming a thread in the wall of the shock. Keep the piston still and remove the shock from the clamp. The cylinder is full of metal shavings, so moving the piston could damage the shock internally. Rinse out the shock thoroughly with water.
4Tap the blade of the chisel or spatula into the rim of the cap at the end of the shock. Work all the way around the edge until you can lift it out. Push the seal head down and pry the snap ring out of the recess at the edge of the cylinder. With the snap ring removed, the seal head should lift out, along with a quantity of oil. Avoid compressing the shock as you do this.
5Measure how far the dividing piston is seated inside the cylinder and mark the position. Thread the valve into the drilled hole and connect the pump. Pump air into the shock very slowly and carefully to drive the dividing piston out of the shock cylinder. Do not pump too vigorously or the piston will fly out of the cylinder at a dangerous speed.
6Clean and rinse all the internal components, making sure they are free of metal shavings. Slide the dividing piston into the cylinder up to the mark you made in Step 5. Refill the shock with oil and replace the snap ring and seal head. Replace the end cap and repressurize the shock up to the desired tension, using the pump.
