Put simply, the function of your vehicle's suspension is to enable up and down movement. And that movement creates vibrations and noise which travels into your vehicle's cabin... and if it wasn't for suspension bushes, the noise and vibration in the cabin would be much, much worse.
Suspension bushes uncovered: All the questions you could ask.
Suspension bushes are essentially cushions mostly made of rubber and polyurethane. Mounted on car suspension and steering joints, bushes absorb road bumps, control the degree of movement in the joints, and minimise noise and vibrations.
Anything else you could possibly want to know should be covered in the following Q&A:
How long do car bushings last?
Bushes usually expire between 90,000 and 100,000 miles, although they may wear out quicker should your drive often involve things like large potholes, or if you've had a high impact collision. Individual components like ball joints might also wear out.
How often should bushes be replaced?
At the front or lower control arm, bushes should be replaced at least once during your vehicle's lifetime. Unavoidable aging symptoms include the rubber drying up and leading to bad cracking.
Is it safe to drive with bad bushes?
While a bad control arm bushing is not technically unsafe, it could still mess with your driving experience.
How many bushes does a vehicle have?
Control arms typically have two bushes, in some cases only one, depending on the suspension design.
What does a faulty bush sound like?
If you hear a knocking or a thumping noise, particularly when going over bumps, this may mean there is worn bad control bushes in your vehicle - the sound is caused by worn bushes ceasing to hold the control arm in situ, so it moves around.
A little known piece of priceless information about bushes...
...if your vehicle is pulling to one side, it's not necessarily wheel alignment or tyre pressure - it could also be bad bushes!