9 Common Suspension Problems and How to Diagnose Them
The suspension system is designed to increase the road holding ability of a car and offer a degree of ride comfort, though that may be less important to a track day enthusiast. The suspension also isolates the chassis and important components from vibrations. Without suspension, your car would likely fall to pieces!
The suspension system on a Caterham kit car
The suspension system is made up of a number of components:
- Damper / Shock absorber / Struts
- Coil spring
- Upper and lower control arms
- Control arm bushings
It is these components that are designed to work together to increase the number of contact tyres have with the road and smoothen the cars handling characteristics. Without suspension, your track car would flop around as though it were weeble.
Suspensions systems are constantly wearing whilst a vehicle is in use and so they begin to lose effectiveness over time. It is important that you constantly monitor the performance of your suspension, especially in cars that are raced or driven hard in competition.
We've put together this simple guide that will help you identify some of the common symptoms of failing suspension parts.
The car feels like this?
Symptom #1: Rocking Back And Forth
If you notice your vehicle rocks more than it used to, front to back, side-to-side or nausea inducing the combination of both, then it is a sign that your dampers are producing less damping response. The car is now swaying on the springs, which will create this perpetual movement.
You can test this by pushing down on each corner of the vehicle if one corner continues to shake after you've stopped applying force to it and takes a long time to settle to a rest, chances are the damper has failed.
On the track, the effects of this will be pronounced with willowy, barge-like handling and a magnifying of every bump.
Steering wheel feel heavy? Is it shaking?
Symptom #2: Steering Wheel Judder / Heavy Steering
A steering wheel that judders on an otherwise straight piece of the track are an indication that your suspension could have failed or any number of bushes have worn. This should not be ignored as it will only get worse, until the point of total failure.
Keep an eye out for a "bump steer" like sensation, where the car will quickly jolt and change the course of its own accord, again this points to suspension problems. Another sign is the car diving in corners or veering to one side.
Even mild crosswinds could highlight suspension issues, if you find that you have to over-correct in even slight breezes, something is not right. The body of the vehicle is catching the wind and acting like a sail, introducing a veer counter to the direction of travel.
During hard turning, if you feel a dead spot in the steering, or the wheel is resisting your input, this also could be suspension trouble. This might also point to worn bushes in the steering system.
Symptom #3: Noises
A well-maintained track day car shouldn't make any out of the ordinary noises. It is important for drivers to listen for anything untoward and be observant of unusual vibrations. Knowing how your car sounds normally will help you pick-up on problems early.
Failed components will sometimes make loud clunking or squeaking noises when traveling over bumps or clipping a pronounced apex kerb. Deep, low clunking noises could be a failed strut that is offering no rebound whatsoever. A muffled thud might be the car bottoming out on its bump stops. A loud crashing noise could be parts smashing together because of the suspension as destroyed your rubber stops.
A particularly bad leak on a coilover
Symptom #4: Leaks
Shock absorbers, dampers, and struts are all sealed units. Inspect them regularly for signs of leaking oil. In a perfectly operating damper, there should be no visible leaks.
You may have to take your hand and wipe it around seals to inspect it more closely. If you feel a wetness on your fingertips, determine whether it is just water or oil. Check under rubber boots too and it's worth purchasing inspection mirrors & lights to include in your toolbox for hard to reach areas.
Symptom #5: Wobble
After each event, take time to jack up your car and then support it safely on stands. Check each wheel for any obvious slack or excessive movement. Place your hands at 12 and 6 and then 9 and 3, gently rocking the wheel. If you sense any slop or hear any knocking, check your suspension and control arm bushes. Be careful not to unsteady the car to the point it topples off your jack stands.
Symptom #6: Excessive Weight Transfer
Under heavy braking, if you notice weight transfers rapidly and almost unopposed to the front end, inspect and adjust your front suspension. If the suspension is offering less support and resistance, the weight shift caused by braking will be exaggerated. Your front end could even bottom out on the track. This will also unsteady the car in turns and force the driver to ease up on the brake pedal.
On the flip side, under acceleration, if you notice the same issue at the rear, you'll need to inspect those dampers.
Symptom #7: Abnormal Tyre Wear
Tyres should wear evenly across the board, except in cases where you are running large amounts of negative camber. If upon inspection, a tyre appears to be wearing unusually, or differently to it's opposing counterpart, you may have an issue on your hands. Check for high or low spots or places where the bead wiring has begun to poke through the rubber.
Tyres are one of the key ways you can tell something is not right with your car, so it's worth evaluating their condition frequently, even after each run if time allows.
Symptom #8: Rusted / Pitted Rods
Rods are usually treated with a chromium outer coating for corrosion resistance. If this protective layer breaks down and the rods become pitted with rust, it will increase resistance and cause jerky operation. This will make a car unpredictable, so when looking over your suspension, keep an eye out for this.
Symptom #9: Car sits wonky or low on one side
Most racing cars are set to run a positive rake angle, with the front end lower and some might be set so that they are level when the driver is sat behind the wheel. But if a car is sat at an odd angle, something is probably wrong, especially if it's only noticeable on one corner. We're talking differences of 1/2" sometimes. This could have been caused by a cracked spring or a bent shock after a crash.
Final Thoughts
The suspension system is critical to a car's safety and handling. Check yours often and carry out simple maintenance such as frequent underbody wash downs to reduce corrosion. If a damper is leaking, have it rebuilt and serviced. Prevention is always better than having to find a cure.