Shock Absorber Maintenance Checklist
Track use, whether on or off-road can be punishing on your suspension system. We've put together a guide for maintaining your shocks and suspension components. Depending on the type of circuits your racing on and the level of competition events you enter, you'll want to repeat this checklist after every race. Maintaining a race car will make it more reliable and therefore, more competitive.
The checklist assumes normal wear and tear from track use. If you get into a crash, get airborne during the race or are competing at a track with a rough surface or big curbs, you should inspect the suspension even more rigorously. It will be easier in some cases to remove the shocks for inspection. This has the added bonus of getting you familiar with removal and refitting process in case you need to swap a damper during an event.
Item 01: Clean the Shock
Cleaning your shocks should be done as often as possible. It is easy to spot leaks for example on a clean shock absorber. But keeping them clean will also help the seals last longer, with dirt & grit less able to break down the rubber. You can typically use any traffic film remover or liquid soap that is safe for use on rubber materials. If you are using a pressure washer, be careful to not aim the spray nozzle directly at any seals, which could force water inside the shock. A soft brush will help remove any stubborn build up of muck. Dry off with compressed air or a microfiber towel.
Item 02: Damage to Shock Body / Coil Over Threads
When inspecting for damage to the shock body, you are looking in particular for dents or cracks. If a shock body is dented, the rod may no longer operate smoothly. The uneven response from the opposing shocks will create a real handful for the driver. This especially applies to mono-tube shocks, on a twin tube body, the dent may not be noticeable in operation.
Check too that a threaded coilover has no stripped threads.
Either way, a cracked or dented shock body should be replaced.
Item 03: Spring Damage
Coil springs can snap over time. This is likely to happen in areas where powder-coating has chipped off and the underlying metal has begun to rust. If you spot a stone chip anywhere on your shock or spring, it's a good idea to clean the area and paint over it, preventing the corrosion from spreading.
A snapped spring is extremely dangerous if you find that your spring has deformed or cracked, replace it immediately. Failing to do so could cause additional damage to the car, including bottoming out on your oil sump. You will likely also hear clunking and banging noises whilst driving.
Item 04: Leaks
Wearing rubber gloves, inspect the coilover or strut for leaks. Shock oil is almost entirely transparent, but you'll see leaks as a wetness around seals, maybe even pooling in the spring seats or splashing onto surrounding parts. Gently feel around the shock for even the slightest amount of shock oil. If you find you have a leaking shock and it is rebuildable, then send it back to the manufacturer for servicing. If not, then you'll have to replace the whole shock.
Item 05: Bushes
Take a prybar and test for any movement in the suspension bushings. Check any bushings on the control arms and trailing arms. If you find there is slack or play in them, replace them. Worn bushes can cause the suspension system to operate less effectively, to bind up or begin to place extra stress on other parts. Many track car builders chose to use polyurethane bushes where possible, they are easier to replace than factory metaplastic ones and available in varying grades of hardness for improved handling response. Again, you may notice worn bushings whilst driving from the dull clunking type noises the bush makes as it moves around.
Item 06: Fixings
Check fixings too for wear. Sometimes, during the fitting of parts, shock mount bolts can become damaged by cross-threading occurring. Fixings can become worn over time. Always refit suspension bolts to the correct torque settings so as to not over tighten them. Also, check tie rod ends and castellated nuts for damage or missing cotter pins. Constant wear on bolt threads can wear them down. Nyloc locknuts should be used only once, after removing one, always replace it with a new one.
Item 07: Shock Performance
It is possible to get a rough approximation of shock performance by bounce testing the car. Firmly push on each corner of the car and see how well the rebound is damped. If the car continues bouncing for a while, then the suspension isn't working properly and the springs are taking most of the load.
Taking the damper off the car, it's always best to test them with a dyno if possible. But you can evaluate them by putting the shaft on the floor and giving it a good push to compress the shock. If you feel a spot with less resistance or even none, you may have air within the shock. If you feel a spot of increased resistance, perhaps the rod is bent or a seal has become loose. At this stage, you would want to assess the damper and consider having it serviced.
Item 08: Dust Boots and Bump Stops
Bump stops are the blocks of rubber that the car drops onto once the suspension has reached its maximum contraction. Sometimes they sit under the dust boot, other times it may be a block of rubber attached to the frame. Either way, you should check the condition of the bump stop. If it is cracked or split, it will need replacing. Because these are usually made from a rubberized material, they do wear out and are susceptible to damage from grit and even UV light.
Likewise, inspect your dust boots if there are any fitted. If these are split, they can hold water and debris, causing extra wear on the rods and seals. Replace split boots as soon as possible.
Item 09: Check the Rods
The piston or shaft that extends from the shock absorber body can be exposed to the elements. The shaft is often coated with a corrosion-proof alloy, but if this coating becomes compromised, corrosion or pitting can take hold. This, in turn, can cause the seals to wear prematurely and ultimately cause the shock to fail.
Also, check the shaft hasn't bent as the result of an accident or hard knock. You can do this by extending the rod and turning it around. If the shaft moves around, it is likely bent and will cause tight spots and an uneven ride height.
Item 10: Check, Clean, and Oil Bearings
Any bearings within the suspension system should be inspected regularly for failure. Some coil-overs have bearings built into the top hat or shock mount. Bearings can be cleaned first by using a spray cleaner like Brake and Clutch cleaner. This removes dirt and debris from them. Once that's evaporated, apply some light machine oil to protect them and offer some lubrication. The bearings will operate nice and smooth using this method. Always wipe away excess oil as this will attract dirt.
Item 11: Mounts
Finally, inspect the mounts. Check for wear, corrosion, failed fixings and damage to the mount itself.
Following the above checklist regularly as part of your post-race stripdown will prolong the life of your suspension, reduce the likelihood of it failing (because you've maintained it, but also because you find problems before they happen and replace components) and make your track car as competitive as possible.