Xantia brake caliper maintainence ?

Mandrake · Post by **Mandrake** » 28 Jul 2005, 03:32

Hi All,
The brakes on my recently aquired VSX are fairly poor compared to my Dad's SX, (poor "bite") and all along I've suspected crappy hard compound pads so yesterday I finally got a chance to take the front pads out and have a look, and sure enough that was the case, (quite worn, very glazed, and a very hard surface compound typical of cheap pads) so I've ordered some better quality ones.
Meanwhile I was looking at the piston and caliper slide arms with the intention of lubricating them as I usually do on this type of single piston caliper brake system, but it seems that it only has one slide, and that has a permanently attached sliding rubber boot on the slide, with no easy way of getting any grease into the caliper slide ??
If I remove the Alan key bolt on the end of the slide will it come apart in such a way to make it possible to get some grease under the boot and into the slide ? Or am I asking for trouble ?
Also the piston itself has a small rubber boot on the side of it, whats the best way to lubricate the sides of the piston (if any) with a little bit of grease ? Or is this not possible without major hassles or upsetting the handbrake adjuster ?
Regards,
Simon

Kowalski · Post by **Kowalski** » 28 Jul 2005, 06:12

The front caliper slide can be greased, the best results I've had are when I've unscrewed the pin, taking it out and stuck the oil can into the hole and pumped a little bit of oil in. You'll need a torx bit (T-30 I think) to remove the pin, it has a thread lock compound on its threads. If you remove the pin with the caliper fully assembled and the handbrake on, the brake will hold itself together rather than droppoing to bits when you remove the pin.
The rubber boot you can see on the piston is around the outer piston, this is the bit that screws in and out to automatically adjust the handbrake mechanism for pad wear. There is a smaller inner piston inside, you can't really lubricate either one of them separately without a lot of dismantling.

Mandrake · Post by **Mandrake** » 29 Jul 2005, 09:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Kowalski

The front caliper slide can be greased, the best results I've had are when I've unscrewed the pin, taking it out and stuck the oil can into the hole and pumped a little bit of oil in. You'll need a torx bit (T-30 I think) to remove the pin, it has a thread lock compound on its threads. If you remove the pin with the caliper fully assembled and the handbrake on, the brake will hold itself together rather than droppoing to bits when you remove the pin.
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Thanks for the info.
Are you sure its a Torx driver ? Although I didn't shine a light on it it looked to me like about an 8mm Allen key head on the slide bolt, or are you refering to a different bolt ?
<blockquote id="quote">quote:<hr height="1" noshade id="quote">
The rubber boot you can see on the piston is around the outer piston, this is the bit that screws in and out to automatically adjust the handbrake mechanism for pad wear. There is a smaller inner piston inside, you can't really lubricate either one of them separately without a lot of dismantling.
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Ok, I might leave that bit alone then. Sometimes its enough to just work a sticky piston back and forwards a few times, as they spend most of their time sitting in one spot...
Regards,
Simon

Kowalski · Post by **Kowalski** » 29 Jul 2005, 15:06

The caliper slide pin is the bit that the caliper slides on, it has a rubber boot on each end of it. The slide pin is definately a torx, my brother managed to strip the splines out of one and we had to weld a nut onto the end of it.

Mandrake · Post by **Mandrake** » 30 Jul 2005, 15:39

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Mandrake

Hi All,
The brakes on my recently aquired VSX are fairly poor compared to my Dad's SX, (poor "bite") and all along I've suspected crappy hard compound pads so yesterday I finally got a chance to take the front pads out and have a look, and sure enough that was the case, (quite worn, very glazed, and a very hard surface compound typical of cheap pads) so I've ordered some better quality ones.
<hr height="1" noshade id="quote"></blockquote id="quote">
Well, put some nice new pads in the front today, checked the mechanism seemed to be free and working properly, went for a drive and..... a little bit disapointing... a definate improvement, and it is slowly improving over the few times I've driven today, but not the big improvement I was hoping for, and still nowhere near as sensitive or responsive as the brakes on my Dad's SX. [}:)]
Initial application of the brakes feels progressive, but fairly dead and doesn't have the finger touch sensitivity of the other Xantia, and a reasonable amount of pedal pressure is required to get moderately hard braking. Even with very hard braking I can't feel the ABS pulsing so I'm wondering if it is even braking hard enough to (potentialy) lock the wheels.
I suppose I could pop the fuse out of the ABS and try it with no ABS to see if the brakes have enough oomph to lock the wheels, as its really hard to tell with the ABS in circuit and no pedal pulsing.
I was planning to bleed the brakes as well, but forgot to do it, and I also have the rear pads to do yet, so I'll do both of those next weekend. The "silly spring" is also already removed....
Any suggestions ? Although the brakes are up to a level that most people would find "normal" their sensitivity is still very disapointing compared to the other (non-ABS) Xantia. Is there any difference in the pedal sensitivity and initial application on ABS models or do the brakes behave identically up until the point where the wheels start to lock ?
Regards,
Simon

Kowalski · Post by **Kowalski** » 30 Jul 2005, 20:55

I've not noticed any difference between my ABS and non-ABS equipped Xantias, the ABS one does have bigger discs but the brakes are about the same overall, I don't really use them hard enough to overheat the smaller disks.
Do you have any idea what the state of your accumulator sphere is in? That sphere could have an effect.

Mandrake · Post by **Mandrake** » 31 Jul 2005, 03:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Kowalski

I've not noticed any difference between my ABS and non-ABS equipped Xantias, the ABS one does have bigger discs but the brakes are about the same overall, I don't really use them hard enough to overheat the smaller disks.
Do you have any idea what the state of your accumulator sphere is in? That sphere could have an effect.
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The accumulator sphere is nearly flat, and hopefully will be replaced next weekend. However the accumulator sphere is pretty flat on the other car as well... [|)]
Regards,
Simon

Kowalski · Post by **Kowalski** » 31 Jul 2005, 03:24

If the accumulator sphere is completely flat, like if it has a ruptured membrane, you have nothing in the system to smoothen out the pressure pulses coming out of the pump and coming out of the pressure regulator, hence you get brakes that pulse. You do get a degree of feedback through the foot pedal, I can feel through the brake pedal on mine when I put the handbrake on, I wonder whether that feedback with its pulses and the spring in the pedal can combine themselves to give you lumpy braking.

Mandrake · Post by **Mandrake** » 31 Jul 2005, 03:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Kowalski

If the accumulator sphere is completely flat, like if it has a ruptured membrane, you have nothing in the system to smoothen out the pressure pulses coming out of the pump and coming out of the pressure regulator, hence you get brakes that pulse. You do get a degree of feedback through the foot pedal, I can feel through the brake pedal on mine when I put the handbrake on, I wonder whether that feedback with its pulses and the spring in the pedal can combine themselves to give you lumpy braking.
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I don't notice any lumpy braking or pulsing of the pedal at all - in fact the braking is very smooth and progressive, the problem is that it is just not sensitive - it requires a lot more pedal force than the other car for normal amounts of braking, and it seems as if the maximum braking force is also a lot less.
Things that I still have left to do that may affect it are: Accumulator sphere, rear brake pads, and bleeding front and back brakes. If all of those don't solve the problem then I'll start panicing a bit [:D]
Regards,
Simon

XM-V6 · Post by **XM-V6** » 31 Jul 2005, 15:36

Hello Manndrake
Did you put some (only very little) cupper(Or Ceramic) grease to the side off the brake pad metal flange ? It is also important to remove the rust/dust in the caliper/pad touching surface, I did that on my XM using a large screwdriver and be carefull don't hit the piston rubber. Because it is metal to metal here it can give a lot of friction.
And yes the back brakes did make also a difference, after replacing my front discs, pads and cleaning/lube the back-ones my braking improved about 75% (Before impossible to let ABS coming in, now its is responsing like new.
Succes

jeremy · Post by **jeremy** » 31 Jul 2005, 15:57

Simon - If I read this thread corectly you have used a different make of pad on your old discs. Is it possible that the compound on the new pads is a different SHAPE from that on the old ones and they are rubbing on an unworn/rusted section of disc at the centre? I had this on the Zx and even after 10,000 miles the things still hadn't bedded in and in fact I changed the discs as they were cheap and fitted new pads. When I did the job in the first place I'd thought that the discs were Ok and when I came to fit the new ones I wondered why I was bothering as they didn't seem bad at all.
On looking at the old components when I dismantkled there was a distinctive band at the centre of the disc where the pads were running on the rust and had failed to clean the disc. Shaving the relevant bit of pad off would effect a cure. I'd use a wood chisel or similar blade rather than an abrasive to keep the dust down.
jeremy

Mandrake · Post by **Mandrake** » 31 Jul 2005, 16:53

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by XM-V6

Hello Manndrake
Did you put some (only very little) cupper(Or Ceramic) grease to the side off the brake pad metal flange ? It is also important to remove the rust/dust in the caliper/pad touching surface, I did that on my XM using a large screwdriver and be carefull don't hit the piston rubber. Because it is metal to metal here it can give a lot of friction.
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Hi,
All the dust from the old pads was cleaned out of the whole area. There didn't seem to be any rust where you describe.
<blockquote id="quote">quote:<hr height="1" noshade id="quote">
And yes the back brakes did make also a difference, after replacing my front discs, pads and cleaning/lube the back-ones my braking improved about 75% (Before impossible to let ABS coming in, now its is responsing like new.
Succes
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Still have the back pads to go yet, we'll see how it goes...
Regards,
Simon

Mandrake · Post by **Mandrake** » 31 Jul 2005, 17:00

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by jeremy

Simon - If I read this thread corectly you have used a different make of pad on your old discs.
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Yes, the old pads were "Roadhouse" the new ones are "Mintex".
<blockquote id="quote">quote:<hr height="1" noshade id="quote">
Is it possible that the compound on the new pads is a different SHAPE from that on the old ones and they are rubbing on an unworn/rusted section of disc at the centre? I had this on the Zx and even after 10,000 miles the things still hadn't bedded in and in fact I changed the discs as they were cheap and fitted new pads. When I did the job in the first place I'd thought that the discs were Ok and when I came to fit the new ones I wondered why I was bothering as they didn't seem bad at all.
On looking at the old components when I dismantkled there was a distinctive band at the centre of the disc where the pads were running on the rust and had failed to clean the disc. Shaving the relevant bit of pad off would effect a cure. I'd use a wood chisel or similar blade rather than an abrasive to keep the dust down.
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Yes, non flatness of the discs definately crossed my mind, and it is there to a certain extent on any old discs, however it looks to be very minimal. There is no rust at all on the discs.
Today I had another go at things, I took the front pads out again and worked the piston a bit - letting it press out against a bar under pedal pressure then winding it back in again. The left one was initially a bit stiff but the right one moved easily. I also bled both the front and back brakes.
Looking at the pad surfaces after a couple of days of use (including a few emergency stops) the pad surface does appear to be contacting across the entire surface with no obvious band of non contact.
There is a quite definite improvement now - the brakes seem a bit more sensitive and also respond faster. I still wouldn't call them 100% yet, (maybe about 80% of normal) but they are now working well enough that I can feel definate ABS pulsing when I brake hard, and that was not there yesterday.
I still have the rear pads to go yet. (Edit: also the faulty main accumulator sphere to replace too... forgot about that)
Looks like there is no one major clear cut thing wrong as I was hoping for, its just the cumulative effect of lots of smaller things being wrong. Hopefully I won't have to replace the front discs as I would do that as a last resort when all other possibilities are explored. (As I've probably mentioned before, new Citroen parts over here are extremely expensive)
Regards,
Simon