Brakes binding, or normal behaviour?

C.J. · Unread post by **C.J.** » 16 Jun 2008, 22:36

I've noticed over the first two weeks of ownership, that when I come to a halt at traffic lights/whatever, that the car doesn't initially creep backwards/forwards like the rest of the fleet do if the handbrake isn't applied.
However, it does after approx 10 seconds of remaining stationary.

Is this just another Xantia foible, or have I got pending brake cylinder problems?

Unread post by **CitroJim** » 17 Jun 2008, 07:51

Hi Colin,

It's very tempting to say "they all do that sir.." and to an extent I think they do, certainly all three of mine do and you get used to it after a while. It only becomes noticeable (as most things about hydraulic Citroens do) when I drive dad's 205 which has the rolling resistance of a matchbox car with speedwheels on it...

I offer this as a possible explanation: The handbrake adjustment mechanism is via a very fine lead-screw behind the caliper piston which gives exceedingly fine linear adjustment unlike the click-ratchet on most self-adjusting drums and as a consequence the front pads sit very close to the disc at all times. Added to the fact that the front discs are big, the pads likewise, it takes very little to make the fronts bind very slightly. In fact, the fronts run quite hot as normal and this'll expand the disc and could well cause a little binding when you first roll to a halt which reduces significantly as the disc cools off.

That's all just theroy off the back of the proverbial fag packet. More to the point, it will not be time wasted to give all your calipes a good check. Start at the rear. these should not bind at all and the rear wheels should spin very freely indeed. Rear calipers have a habit of corroding to the trailing arm and this corrosion actually pushes the caliper out of line and causes the pads to wear wedge-shaped and if extreme, bind a little. It's a good idea to have the rear calipers off and give the mating faces to the trailing arm a good clean up and a smear of copaslip. Also give the rest of the caliper a good clean-up whilst you are there. To do the job properly, get some new 3.5mm hydraulic pipe seals so you can have the caliper right off to do the job.

Give the fronts a good clean and check, have the pads out and ensure the calipers are very free to slide sideways. Ensure the pads are replaced correctly. Check very carefully the handbrake adjustment is correct and that the handbrake cables or adjustment do not cause binding at full lock. Remember that to get the pistons retracted on the front calipers, they need to be screwed (rotated) back and not forcably retracted like conventional ones. Ensure the pads are correctly replaced by ensuring the pips on the back of a pad sit in a cutout on the piston face.

Finally, it is not unknown for deteriorating front flexi hoses to cause binding due to a ballooning effect. You apply brakes, the hose blows up like a balloon and is thus able to exert a small braking pressure after releasing the pedal.

Flexis are cheap and easy to change and look pretty conventional. No new hydraulic seals are needed. You'll find that LHM does not cause brake system corrosion like conventional brake fluid so seized nipples and unions are practically unknown. It can be a messy job though as LHM loves to drip on your hands as you are changing hoses.

lexi · Unread post by **lexi** » 17 Jun 2008, 09:56

I think you are spot on Jim. Just changed front discs and pads plus one new caliper. Had a slight squeaking and binding effect on new caliper. Stripped it all off and made sure there was plenty of grease on pivoting and contact points. Even took edges off everything with a file. Very slight noise but much better. Still has stiff rolling resistance on slight inclines.

That being said ........Xantia brakes are brill. Also the best handbrake with a disc setup that I`ve had.

pete_wood_uk · Unread post by **pete_wood_uk** » 17 Jun 2008, 12:32

lexi wrote:Xantia brakes are brill.

If you think they're brill now, and you haven't yet done the silly spring mod, then just you wait

. A bit of 12mm water pipe and 10 minutes' work and you can have Real Citroen Brakes (which you may not like, of course, they take a bit of getting used to...) like the world outside of the UK has on Xantiae already...

Pete

Unread post by **CitroJim** » 17 Jun 2008, 12:53

pete_wood_uk wrote: If you think they're brill now, and you haven't yet done the silly spring mod, then just you wait .

I quite agree that Xantia brakes are tremendous and you only realise it when you drive a conventionally braked car which frankly, now terrify me.

However, having done the spring mod on all of mine I found it makes the brakes a little TOO good for my liking and for my passengers as well. There is a limit to how many times they enjoy intimate contact with the windscreen

I've de-modified all mine now and gone back to the spring and the brakes are still very, very good for me. It also helps on the odd occasion I drive a conventional car.

It could be me. I very frequently drive my cars wearing heavy, steel toecapped boots and even when I'm not, my footwear is pretty chunky. heavy boots and no spring is just a tad too much

I drove a Saxo the other day. My footwear choice and the girly little pedals just did not work out at all. I could hardly declutch, much less brake

For those who wear ordinary footwear, the spring mod is good and always worth doing just for the sheer experience of the difference it makes.

pete_wood_uk · Unread post by **pete_wood_uk** » 17 Jun 2008, 16:37

I see what you mean, Jim. I was coming at them from a CX and a Kawasaki, so to me the modded brakes are wonderful.

I'm currently schizophrenically split between a modded Xantia and a C5:

Pete-to-Xantia: "See that piece of gravel over there. No, not that one, that one. Yes, that one precisely. That's where I'd like to stop, please. Marvellous. Thank you."

Pete-to-C5: "I'd like to stop please. Yes, anywhere. Just stop. Soon. Please. Please stop. I'll be a good boy. I've always been good. I've said my prayers. Can I stop yet? I'll say them again. Dear God, please help me stop."

I know that the C5 *does* stop, it seems to stop very well; it's just the lack of control over the process that gets me...

Cheers
Pete

jeremy · Unread post by **jeremy** » 17 Jun 2008, 17:36

Air in the system can also cause a slow release of the brakes. Its not really noticeable on application as you are opening a valve rather than pumping but the LHM can take time to flow back when the pressure is released.

Gas in the majority of the system will be cleared by Citroebics (raising and lowering the car) but won't clear it from the one-way bits - which are the front brakes and the rears after they separate from the suspension.

C.J. · Unread post by **C.J.** » 17 Jun 2008, 22:10

jeremy wrote:Air in the system can also cause a slow release of the brakes. Its not really noticeable on application as you are opening a valve rather than pumping but the LHM can take time to flow back when the pressure is released.

Gas in the majority of the system will be cleared by Citroebics (raising and lowering the car) but won't clear it from the one-way bits - which are the front brakes and the rears after they separate from the suspension.

Well my local friendly Citroen mechanic friend is changing the entire LHM fluid this coming weekend, so I'll see if that makes a difference....and shuts the noisy hissy steering up too.

vince · Unread post by **vince** » 18 Jun 2008, 19:21

tell all, whats this spring mod thing?

Unread post by **CitroJim** » 18 Jun 2008, 21:29

vince wrote:tell all, whats this spring mod thing?

Hi Vince,

The spring mod is to replace the spring which is between the button on the brake dosuer valve and pedal pendant with a solid piece of metal. Originally, Hydraulic Citroens did not have a brake pedal, just a mushroom botton directly attached to the dosuer valve and this gave a really direct and sharp feeling to the brakes. Later, conventional pedals were introduced to operate the dosuer via a rod. In the Xantia, this rod was replace by a spring in an attempt to make the brake feel more "conventional".

Feel up behind the pedal and you'll come across a black tube on the back of the pedal about half way up. Lift the pedal up as far as it will go and pull the black tube out. The tube is in two parts. Lift the collar in the middle of it and it'll separate, revealing a spring. Replace this spring with an equivilent lenth of 15mm copper water pipe, reassemble the tube and refit.

Go for a spin and be staggered at the difference in brake feel. As I say, because of my footwear choice it does not suit me as it makes braking too sharp but it sure makes a difference!