People just don't check their ball joints. It's an unseen part of the car that takes effort and a certain
amount of knowledge to understand what you are actually looking at. The main problem is that these
components are very important and are unfortunately placed in one of the worst areas for corrosion.
The first you normally know about a failed ball joint is the MOT guy walking towards you about to make your day
really shitty with a fail sheet, meaning you have to pay out extra for parts and labour that you weren't expecting.
But it could be a lot worse than that. Early fortwos had an issue with faulty ball joints and the first you
knew about it was one of the front wheels was no longer connected to the wishbone and was flapping
around in the arch. Needless to say, if this happens, you are in deep shit. It will destroy the wheel,
hub, arch, suspension, steering rack, brake lines and your underpants.
The ball joint is the only thing that holds the wheel hub and suspension to the suspension arm.
It has to be able to move and pivot to take both steering and suspension movement but it
must also be incredibly strong to take the punishment.
This is what new ball joint looks like, it is a solid metal block, a stud and a rubber protective boot.
And here is a ball joint in position at the bottom of the wheel hub.
The whole assembly sits 6" off of the ground at the front of the car. It's one of the
first thing that gets splashed in puddles, covered in grit, salt and that fox you ran over.
Needless to say, considering the harsh conditions, they don't last forever.
There are 2 reasons that a ball joint will fail an MOT, either it will have too much play in it
(too much lateral movement) or the rubber boot is split that protects the internals. Too much
unnecessary movement will cause excessive internal wear to the point where the 2 parts could separate.
If the rubber boot is split, all that water, grit and salt can get inside, cause wear and corrosion.
There are 2 checks that you should consider doing
Firstly, jack the front of the car up, hold the wheel at the top and the bottom, push in at the top and pull out at
the bottom. Then pull the top and push the bottom. Repeat over and over. There should be no movement at all.
See the ball joint checking page
Secondly, remove the wheel (for better viewing) and look at the rubber seal of the ball joint.
Give it a quick wipe clean and give it a visual and manual inspection for splits or damage.
If either of these tests fail, you'll have to fit new ball joints. Not just for the MOT, also for your safety.
Joints? Yes, don't just change the 1. Always do both sides at the same time.
Jack the car up and take off the front wheel to reveal the brake disc and caliper.
Unbolt the caliper and zip tie it up to the suspension spring, this stops you stressing the brake pipes.
Remove the brake disc to leave you with the bearing, hub and hub carrier.
You have to remove the metal cap from the centre of the hub. Beat the crap out of it with a
hammer and chisel or screwdriver. Don't even try to remove it intact, just get replacements.
What you uncover is a stretch bolt. It'll be very tight and about 1 mile long (about 5 inches).
Remove it with a Torx E14 socket and the longest ratchet you have (you have a torque wrench right!).
Always fit new stretch bolts, part number is listed below. Refit at 120Nm.
With that bolt out, you can pull the bearing off the stub.
Then remove the metal guard.
Congratulations, you have just revealed the hub. Next thing to do is disconnect the shock absorber.