Pitted Brake Discs

This last week I’ve had a couple of vehicles in with a  brake disc severely pitted, the first being a Peugeot 406 with one of the rear brake discs being severely pitted, this lead to a couple of reasons for failure, one being the severe pitting but it also caused the brake application to be  uneven, although we do not talk about rear brake balance, the mismatch between one side and the other was in the region of 60%.

Initial thoughts on the cause of the problem suggested perhaps the caliper on the pitted side was not functioning efficiently or sticking, however once the pads were removed a thorough check revealed no stiffness or stickiness in operation. Once new discs and pads were fitted the brake operation was checked and the mismatch was down at 5%. Perhaps the vehicle had not been used for a while and the disc on that side of the car had been more exposed to the weather somehow.

Certainly  the Fiat Seicento the following brake disc came from had been laid up for a while (6 mths), the original problem to cause the lay up had been a wheel stud in the drive flange loosening off and causing severe brake judder.

On test the pitted disc had severe judder  and caused severe imbalance in the region of 45%,  this was also dangerous to drive particularly as it was on the drivers side of the car, pulling towards oncoming traffic.

Replacing the discs, pads, the damaged drive flange and studs was necessary.Slight surface rusting of brake discs isn’t normally a reason to fail unless it causes judder or imbalance, however the above examples are extreme and a fail was justified on the amount of pitting alone.

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