xantia rear brake excessive fluctuation

[John Plum]

On Inspection:
The discs didn't spins freely - some binding.
The pins are bone dry.
Only one thin plate had been re-fitted - the others were missing on original (two years back) dismantling. How many should there be - 2 or 4?
Do those thin plates aid separation of disk from calliper or what?

The pads, Although in good condition with plenty of material, vary in mm thickness (side to side to bottom) up to .6mm, and .5mm top to bottom
The copper ease is still evident, but needs regressing.

Of course, there is the question of bleeding too. I wonder if I should fit new pads, probably not.

[John Plum]

BTW, you shouldn't use copperslip or similar metal-loaded grease on any joints that move in normal operation, as it is slightly abrasive and will cause wear.
You also shouldn't use on brake calipers, as it is not temperature stable, and when the brakes get hot, it will run and contaminate the pads (which could be your current problem).

what is the best grease? I want get some now if I need to. Local supplier had no specialist grease to buy, but gave me a sachet from their stock of parts. I also got some cleaner. I'll refit the old pads and bleed now,

[John Plum]

Well, ECP do sell the rear brake kits, with the covers, springs and all.

for my car, an manta 2 estate, the ECP brake kit offered has no covers, pins or springs, so far as is shown on their site. But I found the kit on eBay for £8.52

[Hell Razor5543]

I did enter the details as to your vehicle details, but not using the reg, and I did get a response.

[Mandrake]

Only one thin plate had been re-fitted - the others were missing on original (two years back) dismantling. How many should there be - 2 or 4?
Do those thin plates aid separation of disk from calliper or what?

If you're talking about the thin metal plate on the back of each brake pad that only covers about half the pad its called a bias shim.

It's designed to apply more force on the trailing edge of the pads than the leading edge (for normal forwards rotation) to prevent the pad grabbing on the leading edge. This makes the pads quieter and helps even out the wear as otherwise the leading edge would tend to grab and bite harder than the trailing edge. They have to be installed the correct way up to work.

If you leave the bias shim out its not the end of the world - the pad will wear a bit unevenly (more on the leading edge) and may shudder a little bit in use. If you put the bias plate the wrong way up you'll end up with a wedge shaped wear pattern on the pads and they will not work well at all!

Not sure where you would get hold of new ones if they originals have gone missing though...

[John Plum]

Thanks simon. Are there meant to be two on each pad?

[John Plum]

I did enter the details as to your vehicle details, but not using the reg, and I did get a response.

I tried again, but it insists upon registration number for me.

Im going to refit old pads, with a new sachet of grease donated by local supplier from their kits (no tubes available of specialist grease there), but leave the one bias plate I have out.
The bleed and look for improvement.

[Hell Razor5543]

Well, try using the product code 107545108

[Mandrake]

Thanks simon. Are there meant to be two on each pad?

No just one each. Extra shims wouldn't make any difference to the pad bias.

Every pad should have one bias shim between the piston and the backing plate of the pad, up the correct way.

[John Plum]

Thanks Simon and HellRazor.
I need one more bias plate then.

Put it back together with good clean up and greasing; bled rear brakes.
Actually the rear Wheels do spin OK - with the wheel on. Wheel off I could detect a little aconcentric binding.
The LHM fluid was a little blackish at the wheel extremity.

The MOT failed it on a non-working rear parking brake, as we'll as imbalance across the two wheels. SO, as they know little about the car, perhaps they are making other mistakes when inspecting.

I think, if I load the boot (it was empty) that would help.

[c.morewood]

I think, if I load the boot (it was empty) that would help



Yes that always does. 2 years ago we had 4 breeze blocks in the boot,2 mechanics and myself in the rear seats,trying to get the rear brakes to work on the new mot automatic rolling road!

[Hell Razor5543]

I had one MoT examiner also believe that the hand brake should operate on the rear wheels (but I took off a front wheel and showed him the handbrake cable). I was able to show him why that was a bad idea. I chocked the front wheels, and then sent the Xantia through the full suspension travel. The Xantia did not move backwards or forwards. I then did the same, but with the rear wheels chocked. The Xantia moved a few inches backwards and forwards. He told me that he had learnt something new, and would read up on Citroens with hydro pneumatic suspension.

[John Plum]

@Hell Razor Ah yes James, I read that in a post of yours yesterday while searching of info; nice one!