Shudder on braking
I have a 2005 BMW X5 3.0d Sport. For the past few months there has been a severe shudder when braking at 30mph and upwards. The vehicle went in for its MOT a month ago, so I assumed the problem would be picked up, but the car passed with no advisories. I didn’t mention it to the tester, but perhaps I should have. Do you have any idea what the problem could be? George Gill As the vehicle has just passed its MOT, we should hopefully be able to discard the possibility of wear or play in the suspension joints. Although the brake test in the MOT will show up any imbalance in braking efficiency, it won’t necessarily indicate the presence of distorted brake discs or brake pads which have become hardened by heat or age. The distortion to brake discs refers to a variation in the thickness of the brake disc which can occur over time. This can be caused by either the brake discs not being seated correctly or by hot spots developing on the brake discs and causing variations in hardness that results in the disc face wearing at different rates.
The brake disc runout can be checked with a dial test indicator gauge (DTI) and this may be a good first move in diagnosing the source of the judder. The maximum runout of the brake disc is 0.08mm, although a more acceptable reading would be 0.04mm. Brake pads that have become hard due to age or because they have been subjected to excess heat can also cause a judder at higher speeds.
The Sealey VS0290 brake disc runout test kit.