handbrake/caliper adjustment - thoughts please!

[tim]

Despite my recent post about handbrake cables I haven't really achieved 'closure' on this. The White One now has two new, evenly balanced cables and yet the lever need about 13 clicks and is only just holding. Not good. My idea was to take up all this excess travel by using the adjusters on the cables but Citronut said not to; it seems to me to be a logical way of solving the problem but I tend to respect what the man says. No, there is no 'excess' slack in the cables and the pads aren't worn.
So I stripped out our 'scrappy' caliper to study the relevant parts and I can't see what the problem might be. You have a threaded rod, it bears on the piston, you move it with an arm and presto, you have a handbrake. How can it not work?
How exactly does it 'self-adjust'? The only possibility I can think of is that the previous fitter didn't wind in the peg fully, but thnat is a wild guess only, based on 'wtf else can it be?'
I tried to locate a 'rebuild kit' as suggested by Haynes but I can't find any. Luckily the scrappy ones can donate parts if needed, but the parts look fairly bombproof anyway. So what, when I take off the calipers on the car, should I be looking for?
As an aside, I did my own cables recently and last week I was heading down the open road when a car in front slowed down, I could see his brake lights coming on and off. Sensible, as it was downhill with a damp road. I then realised that he'd actually come to a STOP and his brake lights were flashing on and off. Is this a new gimmick from car manufacturers? Is it actually legal? The moron almost had a ton of BX climbing over his back seat. However, after the full wheel-lock rubber-laying stop, the handbrake was much tighter! Someone else mentioned that in a previous thread.

[citsncycles]

Yep the handbrake adjusts by application of the foot brake. I found with my last BX that hard braking would reduce the handbrake travel, but pulling the lever too hard would increase it again.

[Vanny]

The handbrake adjusts by application of the handbrake. There is a cam controlled by the hand brake lever on the brake cylinder, it is this cam that takes up the slack. Problem is that the cam slips so you need to apply the foot brake to lock the cam while adjusting the hand brake travel.

The lever on the brake calliper is meant to be well lubed with grease. In time this grease dries and hardens, and stops the cam from adjusting. I dont think the rebuild kit will help much, it has a couple of new sliders, a rubber cover for the lever and some grease. I've managed to successfully rebuild a few callipers by taking the rubber cap off, removing all of the grease, and reapplying making sure to work the new grease into the lever and the cam.

[tim]

On my last thread Citronut said about doing the thing with the brake pedal, and that is what I did - made no difference at all. After my emergency stop thing I tried doing the same with the White One - I know Malcolm said not to 'stamp' on it but I did an emergency stop on the way out from Andy's drive, the full monty. Still no change, so there is obviously something wrong with the 'self'adjuster'? Vanny, what you are suggesting is that the mechanism is all gummed up and stiff, and so not working?

[citronut]

if the hand brake cable or the lever on the caliper are not in the fully off position the mechanism in the caliper will not adjust,

maybe Tim you have over tightened the cables,

i also disagree with Vanny the mechanism in the caliper is ment to self adjust with the foot pedal,
not the hand brake lever,

also after fitting new pads you are ment to press the foot brake hard 3 or 4 times to re/set the mechanism in the caliper before re/connecting the cable

regards malcolm

[Dollywobbler]

I had been told (many years ago) that the adjuster worked by pressing the brake pedal and operating the handbrake but have since discovered myself that an emergency stop doesn't half improve the handbrake! Mind you, that emergency stop also knackered up one of my calipers, which is perhaps why the 'don't stamp on the brake' warning applies! (to be fair, it was clearly already suffering anyway).

[citronut]

the reason i say dont stamp on it is you could end up with the contents of you citro blood tank in you drivers side front foot well ,

that is if you protector cap splits

regards malcolm

[RxBX]

....................

I also disagree with Vanny the mechanism in the caliper is meant to self adjust with the foot pedal,
not the hand brake lever,

also after fitting new pads you are meant to press the foot brake hard 3 or 4 times to re/set the mechanism in the caliper before re/connecting the cable

regards malcolm

Spot on there Malcolm

Tim, also check that the pads have been fitted correctly (i.e. that you have the 'Pip' on the pads on the piston side of the caliper and engaging correctly onto the piston groove/slot) as this may affect the correct operation of the self adjustment by not maintaining the correct 'Take up' as the pads wear down !

I've seen some right horror's with incorrect fitment on BX's and XM's front brake pads over the years !

a) where someone's fitted the pads with the 'Pips' fitted to outer-side (non piston side) of the caliper on both N/S and O/S wheel/hubs.

b) Another configuration I've seen is the fitment of both the plain faced pads to one side (of a wheel/hub) and the ones with the 'Pips' to the other wheel/hub.

c) Pads fitted in the correct configuration, but where the 'Pip' on one pad had not been engaged into the piston groove/slot and such, the piston had been pushing the pad such the 'Pip' had damaged the piston face with a slight indentation (From the single point/pressure contact).
This particular vehicle had similar/poor handbrake performance (As your describing) due to this one pad being incorrectly fitted, which was also the only item for its MOT fail.
After fitting a new set of pads correctly , the handbrake performance was reinstated back to normal service and achieved an MOT pass after a retest.

I just thought it was worth mentioning it, as it could be just that ?



.

[mds141]

Richard, does the XM have the same self adjusting mechanism as the BX?

[KevR]

a) where someone's fitted the pads with the 'Pips' fitted to outer-side (non piston side) of the caliper on both N/S and O/S wheel/hubs.

Another favourite is fitting Renault Express brake pads, which are exactly the same shape but thinner pad material, and they don't have the pip on them. Result is the adjuster winds itself up over the next 20-30 miles until the brake is locked...
Don't ask me how I know this...

[Brian]

If after you have carried out all the above suggestions and still have no no joy.

It is not common, but sometimes the curled spring on the shaft has to be located at the bottom end, and the short 90 degree bend of this spring shears off.

But to check means having to dismantle each calliper.

Good luck.

[RxBX]

Richard, does the XM have the same self adjusting mechanism as the BX?

Hi Mark,
Yes, basically the same design/operation on the hub/caliper end but obviously the other end of the cable (inside the cabin) you have the extra pedal for the foot operation, so it really can't be call the 'Hand-brake' so its normally referred to as the 'Parking-brake' .

.

[tim]

I haven't changed the pads - they are simply not that old; a mechanic fitted Peugot pads and this caused the calipers to bind, this was several years ago and the pads were subsequently changed for the 'right'ones. but not by me..... However, this is certainly something to check. I'm pretty certain the spring isn't broken as I have just fitted new cables, don't forget, and both arms are moving happily and snappily. All I can do is strip each caliper in turn, fit new pads and check that everything is assembled properly, then we'll see. But if it's all OK then we are back to the original question!
As it refuses to adjust on the brake pedal I have to assume that SOMETHING is wrong somewhere. And I'd still like to know exactly HOW this self-adjusting takes place. The peg is a screw thread, the arm is dogged to the spring and the peg with a steel tab, and the spring is locked into the arm. So it looks deceptively simple! What exactly do the dished washers do? And what in this set-up is free to adjust itself??

[citronut]

i have never striped one down but im sure i have seen an exploded drawing somewhere ,
that shows two pistons one inside the other and as you press the brake pedal this push's on the inner piston, which wind's its way up the thread as the pads wear down,
so this stops the outer piston any more than it needs to which should keep it adjusted up

the dished washers act as a spring to keep a load on the back of the piston

regards malcolm

[Brian]

Tim wrote:
I'm pretty certain the spring isn't broken as I have just fitted new cables,

The spring that I refer to in my post above, cannot be seen without a complete dismantle.
It's a short tight coiled spring open at the top end and fixed at the bottom with a short 90 degree bend.
The spring is fitted round a shaft so it acts to rotate the shaft in one direction only.
If the spring fixing is lost, then the self adjustent will not function.