Let's face it. Parts break, parts wear our, and we can easily overlook minute issues that can turn into big problems down the road--especially in the harsh environment of a racetrack. What started as a near-perfect race car, suspension component(s), or chassis setup can quickly become just the opposite as wheel-to-wheel racing can wreak havoc on our cars. On the other hand, what started as good race car can slowly change over the course of a drama-free race season, and with so many parts working together dynamically, diagnosing a problem can become frustrating and time consuming.
The halfway point of the race season is a great time to give the chassis and suspension of your race car a good onceover. We know the majority of racers are in tune with their race cars and have their hands on the major components on a regular basis. But a solid inspection and some preventative maintenance can go a long way--especially in the second half of a season when you're chasing a championship.
Preventative maintenance is extremely important for a number of reasons. Catching issues early can help you avoid problems on track, and in many cases can be much less expensive and time consuming to fix before it turns into big problems. Another benefit is a more thorough knowledge of your race car. The more familiar you are with your chassis and suspension, the easier it will be to locate and identify problems that might have otherwise gone overlooked.
Over the next few pages, we are going to cover 10 of the most important parts of the chassis and suspension to inspect and service around the mid-season point. Much of what we are going to talk about works together, and can be the difference between a properly and ill handling race car.
Shocks are an extremely important component to any race car. They control the distribution of loads as the chassis adjusts to load transfer. Over the course of one short feature, shocks perform an incredible amount of work--especially if you consider how much most race cars weigh. As a shock cycles, it also creates heat, which can shorten the life of seals and oil's viscosity, effectively changing the shock rate.
After a thorough cleaning, inspect all four shocks for leaks, bent shafts, and internal damage. Cycle the shocks to ensure operation is smooth and have them dyno'ed if possible. Setup changes over the course of the season can affect not only what shock rates are needed, but could requre a different shock package.
To complete the inspection, check the shock mounts on the A-arm and the chassis for any bent tabs, and cracked welds. The shocks handle a lot of weight. Bent and cracked mounts are very common. Again, a good cleaning may expose a problem that was hidden by a little dirt build-up from being on track.
A thorough inspection of your race car and all of its major components is a great way to prepare for the second half of your race season
Roll Center or Moment Center is one of those unseen things that can negatively affect a race car, when everything else looks right. Checking to ensure roll center hasn't changed is extremely important, especially because changing ball joints, installing new length control arms, installing new spindles (they are not all the same height usually, even if they are stamped the same), and use of different tires with different circumferences (this changes all of the chassis mounting point heights) will all change the roll centers.
If adjustments need to be made at this point, go back and recheck your bumpsteer and toe settings after getting the roll center where it needs to be. Changes in control arm lengths and angles affect the arc on which the ball joint travels, and that affects the bumpsteer.
In reality, your alignment should be checked before every race. At the very minimum, you should be checking caster, camber, and toe weekly. As part of a mid-season refresh, or anytime you change any front or rear suspension components, the alignment needs to be verified.
Verify that the alignment is where is should be. This includes Ackermann, bumpsteer (could have changed with caster changes or spindle changes), rearend alignment and rear steer (trailing arm angles), and toe (front and rear). With so many moving parts in both the front and rear suspension, it isn't uncommon for tolerances to change, parts to move, and alignment specs to change. Slight alignment changes can make huge handling differences on track, and that could be the difference between winning and losing.
A-arms, like any other link connecting the chassis to the wheels, usually see large amounts of load. These links, especially ones that change dynamically during the course of a race, take a beating. The arms themselves, plus the mounting points, and the spindles are all susceptible to wear from normal use. Visual inspections will usually uncover any issues, but slight bends might not be noticeable to the naked eye. Make sure none of the arms are bent or damaged, and with them removed, check for cracks in the welds and ball joint straps, and check for rust. A build up of dirt can cause rust to weaken the material. Make sure the bushings are free and the arms move freely before reinstalling the arms.
Check the body of all shocks...
Check the body of all shocks for damage. Dents, cracks, and leaks can all be or lead to damage that will affect handling.
When using a coilover setup,...
When using a coilover setup, be sure to inspect the spring mount for wear. Be sure to also inspect where the spring contacts the cap.
The shock shaft seal is another...
The shock shaft seal is another important part to check. A leaky seal can lead to shock failure.
Moment center is extremely...
Moment center is extremely important, and needs to be checked whenever parts are changed. Changes of most major components will affect the roll center.
Wheel alignment is huge and...
Wheel alignment is huge and should be checked often. Caster, camber, toe, Ackerman, and bumpsteer all need to be set.
Specialized alignment tools...
Specialized alignment tools are available to make the job easier, like the laser level shown here.
All rod ends need to be checked...
All rod ends need to be checked for dirt and debris, as well as excessive wear. Any worn or cracked rod ends need to be replaced.
A-arms should be checked for...
A-arms should be checked for bends or cracks. Bent A-arms should not be used.