Date: Fri, 08 Sep 2000 15:50:55 +0200 From: Robert Brown <rjbnopsamnetnospam.se> Subject: Re: brakes go CLUNK!
Hi, This is a "feature" of the older style Girling brakes, once they start getting worn. These were fitted to the earlier classic 900's / 99's / 90's until somewhere about 1987, at which point more modern-looking calipers were used. The (giant sized) yoke plate is designed to move towards the centre line of the car when the brake pedal is pushed (this of course causes the outer pad to push on the disk). At the same time, a downward force is applied to the yoke (if car is moving forward) due to the spin of the disk. A new yoke, apart from moving inwards-outwards as just described, has an upwards-downwards play ofslightly less than 1 mm (I think factory tolerance is 0,5 +/- 0,1 mm). On more worn-out brakes, the play can increase to over 2 mm. This means that there will be a significant gap between the cylinder body and yoke *bottom* sliding surface. When reversing and applying the brakes, the yoke will want to travel upwards, and it gets a whole 2 mm or more to do so before hitting the underside of the cylinder body. Thus you get that lovely "clunk". Excuse the wordy description but it's damned hard to explain otherwise ;-) You can get a workshop to weld a couple of shims onto the yoke to reduce the gap, but there's always a risk that the sliding of the yoke will be impaired. Result: excessive outer pad wear and overheating of disks. May be best to put up with the noise until you buy new brakes (reconditioned ones cost about USD 80 (SEK 700) per side). The original poster said that the car was a 1987 model. Not sure which brakes were fitted to that model year, so there's a risk that this info is useless in that case. But the above definitely applies to the 1982 cars. Regards, Robert Gothenburg (1983 900, 1999 9-3 200) theMan wrote: > "Spy" <D.Spynopsameonline.net> wrote in message > news:39B82C7A.A9CF9348nopsameonline.net... > > If I gently apply the brakes when reversing, there is a loud > > clunk from the front brakes. It feels as if something is shifting > > position (shoes?). Brakes seem to work ok, its just a rather > > alarming noise. Is this normal or something to worry about. > > > > BTW it is a '87 900i. > > I have that very same problem on my 82 900, it's a HUGE clunk and it doesn't > sound very healthy. > I have had it looked at but they say there is nothing wrong with it. It > really sounds like something is going to break one day. I am not a mechanic > at all but all I can possibly imagine with my car is that I didn't get the > break cylinder back properly when I changed pads.