A 'Clunk' on BX front suspension

PJ · Post by PJ » 05 Jun 2003, 16:05

I own a BX 19GTi and it produces a nasty sounding 'Clunk' when the brakes are first used when going backwards. The typical scenario is reversing into a parking place after a drive and the first time the breaks are applied - 'clunk'. I had a similar problem on a previous BX which was solved completely by replacing the track rod ends. So, feeling smug, I changed the track rod ends on this one and it did absolutely nothing[:(]
Candidates for the problem could be Brake callipers; Swivel Ball Joint on the suspension arm; Subframe/Front suspension arm bearings; other?
Interestingly - if when in reverse, I slow the vehicle down on the clutch - using first gear, then no 'clunk'!
Does anybody have any suggestions or tests I can do to track the problem down? Or any similar tails that may suggest a trend?
Thanks in advance
Paul.

alan s · Post by **alan s** » 05 Jun 2003, 16:18

Paul,
You've got two options; first is that for some reason, non genuine brake pads seem to be more likely to do this than non genuine...nobody can explain why. It has been suggested that the anti-rattle clips may not be fitted correctly. If it only happened after the brakes had new pads fitted you can do no more than to start there.
Option two is to spend a bit of time & no money on the front end. I have long found that in the case of BXs in my experience and no doubts time will also tell if later models also suffer from the same thing, that ball joints associated with the front end/steering, tend to get water in them, partially seize & then begin to make a cracking sound when forced to turn in a certain direction. This is a noise not dissimilar to a small bore rifle shot at times...keeerrraaack!! I have devised a way of both freeing them up & also improving the ride whilst eliminating the noise in the process.
Check out this link as I feel you'll find it should be of some help.
Let us know if & how it works & if necessary, we'll come up with more but usually, this sorts it.
Alan S
http://www.aussiefrogs.com/snippets/bx_clunks.htm

AndersDK · Post by **AndersDK** » 05 Jun 2003, 17:52

When servicing the brakes - you find that the BX front brake pads DO have some play - even from new.
Seems most of this play is designed to ease the replacing/fitting of pads.
Usually the pad springs should readily take this play - but going from stop to reverse & then apply the brakes - the pads move a bit compressing the springs - with a resulting end-stop "clonk" sound from the pads.
First time noticed - a bit scary - but nothing is wrong with your BX front brakes - unless a garage fitted springs incorrect - or (once in my case) did'nt fit them at all.

Post by **Jon** » 05 Jun 2003, 18:14

Also worth securely jacking the front of the BX up, putting it in low, then use a lever bar to check for play in the front arm bushes.
When they're badly worn, the whole arm can move when you reverse, causing a terrible clunk!

tomsheppard · Post by **tomsheppard** » 05 Jun 2003, 19:33

If you had ever owned a Saab 900 you wouldn't worry about it. It is known as "Saab Clonk" and has crossed the species barrier. It is usually incurable but benign. The pads are lifted when the wheel rotates in the reverse direction. Unsettling at first, but you get used to it.

PJ · Post by PJ » 05 Jun 2003, 22:54

Thankyou all for your comments. I think the favorite is brake pads and springs. I will look at these - change if nessesary - check spring positions and see what happens.
Thanks again - let you know what the result is.
Paul.[:)]

jeremy · Post by **jeremy** » 06 Jun 2003, 12:21

I keep seeing references to springs on the front brake calipers of BX's and am always curious as to what is meant - or is my car missing something?
I have a thin strange looking springy device for each front pad but the only function of this is to steady the pad wear warning sensors, and they simply fit around the forward horn of the pad and are trapped between that and the caliper when the locating bar is fitted.
Should there be a spring and if so where does it fit?
Incidentally my car does make a good clunk from the brakes when the direction of travel has changed. I find it quite re-assuring as at least everything hasn't seized solid!
jeremy

Post by **RichardW** » 06 Jun 2003, 12:55

That's the spring in question Jeremy. Its function is actually to stop the pads jumping about - it's called and anti-rattle spring. Has nothing to do with this clunk which is due to wear in the caliper slides etc, and poorly fitting pads which all slide about when you apply the first time in reverse. Bendix pads reduce this a lot.
Richard

PJ · Post by PJ » 06 Jun 2003, 18:28

Well, I changed the front disc pads and noticed that the right hand side didn’t have any springs at all. I then investigated what the springs should be doing.
They seem to serve two purposes:-
1. As Jeremy stated - they steady/hold the outer brake pad wear cable.
2. When fitted correctly they pull the pad radially outwards removing any 'radial' slack. This puts the pad in a position where any 'angular' slack is also removed.
If the spring is not fitted correctly - or not fitted at all - as with mine, then the pads have some (not a lot but enough) angular slack. This means the pads can be ‘snapped’ back to the other end of their angular travel when the brakes are applied in alternate directions, resulting in a ‘clunk’ at the first application of the break pedal.
Anyway, after ensuring that all was where it should be, I test drove the BX .. And … the ‘clunk’ was no more.[:)]
So … many thanks to you all – this forum has been very useful.[:)]
Regards, Paul.