Disc Brakes xantia 1.9td 1994

frigate · Post by **frigate** » 05 Sep 2003, 23:59

I`am on my 2nd pair of front Brake Discs in a year due to them warping anyone got any ideas what could be causing them to warp.

AndersDK · Post by **AndersDK** » 06 Sep 2003, 00:52

Sure using genuine Bendix parts ?
Alternatives are a bit reputed on the problem you describe.
Other than that new discs MUST be allowed to run in against the pads - a few hundred miles with a light foot on both the acc & brake peddles.
Caning the car in everyday use costs you - in all aspects.
Other problems known are leaking drive axle gaiters - splattering grease on the discs - or leaking brake lines.
Some garages do such hasty jobs - they don't even care about cleaning fingerprints after assembly - or don't bother cleaning off well enough the stain protective layer on new discs.

pete.fair · Post by **pete.fair** » 06 Sep 2003, 02:35

had a similar problem earlier this year, after getting a new set, I checked the hubs and found a few bits of rust stopped them from sitting flat, once removed with a bit of emery paper, fitted the new ones with new pads and have had no problems since, hope this helps

Dave Burns · Post by **Dave Burns** » 06 Sep 2003, 04:48

Earlier this year my Xantia 1.9TD decided to destroy two sets of discs one after the other, first set were Bendix and the second were Brembo, I clocked them during fitting and they were well within tollerance, when they went bad I clocked them before taking them off and they were well out.
The next set I fitted (and I am very thourough in my work so I know dodgy fitting is not the cause) are still on and I have no problems at all with them, and infact they are Brembo's again.
I can't understand what happened to cause this, I went over the front of the car with a fine tooth comb and couldn't find anything wrong, I renewed the suspension rubbers just in case but the ones that came off weren't buggered, and even if they had been I can't see how that could affect the braking to the extent that the discs would warp.
I have never had a disc warp on any other car before, maybe I was unlucky and got two sets of bad discs but I vary much doubt that so I'm stumped on that one.
Icidentaly if you are going to clock the discs with dial test indicator to make sure they are true, its no good just putting the two countersunk screws in to hold the disc, you must also bolt the discs onto the hub with the wheel bolts using appropriate spacers, only by doing this are the discs forced tight against the drive flange as they will be during service, if not you will get a false reading.
Dave

jeremy · Post by **jeremy** » 06 Sep 2003, 13:22

Dave - I know you will have fitted the discs very carefully and removed any corrosion etc. I recell when I bought a pair of front ones for my BX when I first got it they came with a leaflet explaining the importance of getting everything clean and they calimed that a very high proportion of warping was due to poor fitting (75%?). This however must mean that quite a number failed for other reasons.
I'm amazed that anyone can manufacture and distribute and sell a highly machined article like a brake disc for £10 +VAT and although they look very good when cleaned up ready for fitting I do wonder about the quality of the material used etc.
Just a thought about your warping discs - did you use the same pads? If so is it possible that they had a ridge or lump which caused a excessively hot band when the brakes were applied? I know when I fitted bew pads to our ZX (bendix) front brakes with marginal discs I was able to get strange hot smells for quite a while presumably due to local overheating. I've never smelt my BX brakes despite what I would have considered harder use and both are on delphi pads (as they come with warning light wires).
jeremy

Dave Burns · Post by **Dave Burns** » 07 Sep 2003, 03:29

Jeremy, first set of discs that went bad were Bendix and with (new)EBC pads, the second set were Brembo and with (new) Textar pads, those same Textar pads (since they were still flat) are now on these third set of discs (Brembo), this time though its all hunky dory so far touch wood, they have now done a few thousand miles and are as smooth as silk, can't weigh it up, never known the likes of it before.
The specified max. runout according to the H book is only 0.05mm, (a gnats less than 2 thou) so when I fitted these discs and got readings of 0.02mm and 0.015mm then its a sure sign that they are correctly fitted with no crap about and that the machining is as about as good as it gets for a brake disc.
The discs that went daft ended up with a runout of between .07mm and .09mm, I clocked both faces before removal and they were definately warped as opposed to unevenly worn, so little out of tollerance yet they shook the car to buggery when braking from speed.
Dave

jeremy · Post by **jeremy** » 07 Sep 2003, 04:41

Dave
I wonder if disc warping has anything to do with cooling. If the car is stopped with hot discs the pads touching could either conduct heat away from the disc or alternatively insulate it keeping the heat in the contacted area - either way producing a stress in the disc. It could be that after a bit of use the discs become annealed and more resistant?
jeremy

Dave Burns · Post by **Dave Burns** » 08 Sep 2003, 02:06

Hmm...I think if that were the case Jeremy there would be many more post's on here about the subject.
Applying the parking brake to a hot disc is bound to affect its even cooling, question is what do we call a hot disc, my car doesn't get driven in a fashion that gets the disc very hot, being of the old school of driving, you know where you actually use a lower gear for descending steep hills and slow down in plenty of time.
Followed a bunch of cars down a steep hill today infact and the stench of brakes was awfull, hehe perhaps the problem is that my anchor's don't get pained enough.
Dave

algieuk · Post by **algieuk** » 08 Sep 2003, 03:54

I expect you have checked it, but how about the caliper slide? This may be OK when the calipers are free, but under load they might be binding and causing the caliper to pull the disk out of line when braking. If it did this while hot it could introduce a permanent warp.

jeremy · Post by **jeremy** » 08 Sep 2003, 04:37

Nice to come accross someone who drives like I do Dave. What always surprises me about Citroen diesels is how little engine braking there is considering the enormous compression.
I started to drive on a 1946 Austin 8 which had rod operated drums and on which the handbrake simply pulled on a cross-shaft and worked on all 4 brakes - very handy! That would fade without much trouble and I've found very few that wouldn't under what I consider quite modest braking - so use of the gears and not relying on brakes.
I'm sure everyone thinks im nuts!
Jeremy

AndersDK · Post by **AndersDK** » 08 Sep 2003, 05:37

Nut at all Jeremy [:D]
Comes with grey & diminishing hair growth - and the turkey head staring at you from mirrors.

Dave Burns · Post by **Dave Burns** » 10 Sep 2003, 04:21

Jeremy its good the have a high compression ratio for engine braking, whats not good though is to have the energy contained in the compressed air during the compression stroke, returned to the piston on its downward stroke, this negates most of the benefit of the high compression.
Don't know if you have ever driven a heavy lorry with a jake brake fitted, this is powerfull engine retarder and works by opening the exhaust valves momentarily as the pistons near the end of the compression stroke, thus venting the compressed air, then there is no energy to push the pistons back down, the service brake hardly need be used when a jake is fitted, as long as you are prepared to stir the box and keep usefull revs on that is.
Dave

pete.fair · Post by **pete.fair** » 11 Sep 2003, 02:14

Just a thought, but is it the disc that is warped or you just have a wheel vibration. A problem i had turned out to be a defective tyre (oval) that gave a rotational speed related wobble making me think it was dics warp. Had your tyres changed recently?, if so, maybe worth checking