The spring caps support the...
The spring caps support the load of that corner of the car. Make sure they are in good shape and not worn excessively or cracked. These are just the kind of cheap, replaceable parts that can ruin your race day.
In the case of a sealed shock, it's always a good idea to send the shocks to the tech center for evaluation, dyno-ing and/or rebuilding or replacement. In this case, maintenance by the team is not a choice and all we can really do is hand cycle the shock and look and feel for obvious damage externally.
If you have user-serviceable shocks, then read on, and we'll tell you how to proceed with your maintenance. This still means you should visually inspect the exterior of your shocks before disassembly.
Look for obvious leaks, shaft damage such as a bent shaft, scratches, or scoring. A discolored shaft is a sign that the internal temperatures are too high and the oil may be burned. Nicks and dents on the outside of the shock body may have carried through to the inside walls of the shock restricting movement of the piston.
Inspect the rod ends for corrosion, excess wear, and damage such as dings and cracks. If a shock was bent in a collision during the season, many teams will remove and reuse the rod ends. They might have missed damage in the heat of the moment. Now, we can take time to do a thorough inspection after the ends have been cleaned.
Before you disassemble your...
Before you disassemble your adjustable shocks, record the settings. You will want to return them to the positions where you left off last season. Turn the compression adjuster to the right and count the clicks to full lock. Then write that down. For the rebound adjuster, move the wheel from left to right facing the shock with the rod end down. Again, count the clicks to full lock and record.
Cycle each shock by hand. Place the shaft end of the shock on the floor and push the shock in or down and note the resistance. This gives somewhat of an indication of its condition. Feel for spots where the shock movement is easier or harder. This indicates a bent shaft or scored inside wall. Clamp the shaft end and pull on the shock in the same way.
Gurgling sounds and skipping are signs of cavitation and indicate that gas may have mixed with the shock fluid, or the seal separating the compression fluid from the rebound fluid has leaked or worn out. I've had shocks that were either very easy to move or solid and did not move. Amazingly, the driver could not tell us that the shock was stuck.
Once you have carefully inspected the exterior, we can disassemble the shock and evaluate the interior parts. Look over the threads that are a part of coilover shocks for height adjustment. These can be repaired if they are dinged or worn by filing. The adjuster ring should spin freely with no sticking anywhere along the range of motion you will be using. A light lubrication can be applied later.
INSPECTION OF INTERIOR As we disassemble the shock, we'll see the shock oil first. Note the color and texture of the oil. If it has endured high heat and been used too long, it will appear dark and smell somewhat burnt. Strain the oil to look for material that may indicate a decomposing seal or broken parts.
This shock cap has been rubbing...
This shock cap has been rubbing on the frame or shock mount. This can have a huge affect on the motion of the suspension. Conflicts such as these can ruin an otherwise great setup and will be very hard to find. Look over your installation when mounting the shocks onto the car. They should not make contact with anything on the car in a full range of motion of the suspension. The cap shown made hard contact and that definitely affected the car's handling.
Note the condition of the shaft seals along with the O-rings around the piston and the piston seal. With gas pressure shocks, the floating separator piston needs the same inspection.
Look at the valve discs and see if they are still sealing well. Inspect the inside wall of the shock body and look for inward facing dents and/or scratches. The wall should be pristine in appearance or the shock body will need replacement.
Once the piston/valve assembly has been disassembled, look at the valve discs. Sometimes these will have burned oil caked on them in the pattern of the piston and will need to be replaced. The chance that they could be reassembled in exactly the same position is a long shot at best. If not positioned correctly, they would leak and affect the overall shock operation.
MAINTENANCE Shock maintenance is a process that depends mostly on the extent of use. A team that races 20 races a year will get by with annual maintenance. If you run a more southern schedule of 30 or more races a year, with a few touring races thrown in, you'll need to do maintenance twice or three times a year.