The strength of the BMW M4 Coupé is evident in every detail.
I have said it many times and it still holds true, especially for drivers who are not mechanically minded.
It pays to have your vehicle regularly serviced or at least driven, say once a year, either by a knowledgeable friend or a professional mechanic, to get an opinion of its general condition.
Unfortunately, or perhaps fortunately, come to think of it, wear on any moving parts is normally gradual and the regular driver may well be unaware of brakes that are not quite as good as they used to be, or a clutch lever that no longer operates at the correct level.
Of course, wear in the engine might make itself known by excessive oil consumption or knocking. Wheel bearing wear will show during turns. Universal or constant-velocity joints must be checked for play and after a high mileage the crown wheel and pinion may be past their best.
Wear in shell bearings may often be shown by draining the oil and examining it for metallic particles.
A case I came across recently was severe judder while braking. The car was well maintained and in fact the owner had fitted new brake discs and pads in the past few months. I drove the car and the judder could be felt at the brake pedal and at the steering wheel.
Judder may be caused by warped or distorted discs, but as these were new and of top quality, we could rule that out.
So I removed the front wheels and clamped a dial gauge in position to check for disc run-out and this proved to be excessive.
Your handbook will give you maximum allowable run-out, probably around 0.15mm (0.0059 in). It will also state minimum allowable disc thickness.
A disc that is worn too thin may prove useless under heavy braking, so checking is essential.
The discs were then removed and cleaned off and the disc seating on the hub proved to have quite a bit of dried grease on it and was thoroughly cleaned using a wire brush.
This did the trick and there was no more judder.
Occasionally, when the judder persists, it is worth swapping the wheels from front to rear as this sometimes works. Try using the spare too and if that makes any difference, examine the original wheel for run-out or tyre damage perhaps caused by clipping a kerb.
Generally, judder felt at the steering wheel suggests trouble with the front brakes. If the fault lies with the rear brakes you will probably feel vibration throughout the vehicle.
The rear brake drums should be checked for ovality and minimum thickness and check also for anything more than just perceptible play in the callipers.
Wear in steering and suspension bushes may also contribute to judder, so give them a look too.
If you do not have access to a dial gauge, the old fashioned way of using a pencil works well enough. Secure the pencil to the calliper with the point touching the brake disc.
Turn the disc and, if there is run-out it will show as a gap between disc and the tip of the pencil. - Star Motoring