Uneven breaking

cox377 · Post by **cox377** » 17 Jun 2010, 10:11

Hello Guys,

I’ve got a query, does anyone know what would cause uneven front / rear braking, or in other words over heavy rear braking on a Mark 2 Xantia. The brakes were working fine and the pads are fine all round.

I think I’ve noticed the suspension being slightly off balance as well when driving along, but that maybe in my head.

Much appreciated as always

coXen

Post by **Peter.N.** » 17 Jun 2010, 10:14

Are the rear wheels locking up?

cox377 · Post by **cox377** » 17 Jun 2010, 10:42

they have done when really anchoring up.

citronut · Post by **citronut** » 17 Jun 2010, 13:09

its not just when you have the car loaded up with building material and a trailer full as well,

regards malcolm

cox377 · Post by **cox377** » 17 Jun 2010, 13:25

nope, she was carrying no weight

I've noticed the back going down a little bit when breaking, didn't realise quite how much breaking until i had to anchor up.

cox377 · Post by **cox377** » 18 Jun 2010, 08:07

I have added another litre of LHM last night as I know she was running a touch low. No change. Is there a common fault that might cause this on these motors?

Much appreciated as always

CoXen

citronut · Post by **citronut** » 18 Jun 2010, 09:16

maybe your centre rear shphere is flat, so your brakes are drawing from the rear suspension presure,

this could also be why some people call this sphere an anti sink sphere,

as it is actualy a rear brake reserve presure back up,

regards malcolm

G4EIY · Post by **G4EIY** » 18 Jun 2010, 09:40

Loosing LHM quickly from the reservoir without any visible external leaks, is a sure sign that one or more spheres have lost nitrogen into the system.

When this occurs, it does produce rear end drop on braking.

Good luck

cox377 · Post by **cox377** » 18 Jun 2010, 15:27

okay, so I need to change out the centre sphere? the front two spheres look quite new, I've changed the front centre as well. I think the centre one looks the oldest out of the lot.

Malcolm,

Do you have any means of testing the sphere?

James

Post by **xantia_v6** » 18 Jun 2010, 17:21

I don't think that any of the spheres can cause the brake balance to be wrong. Air (or nitrogen) in the brake lines can cause odd effects, but bleeding will fix that.

The brake balance is entirely controlled by the doseur valve.

Can you describe the symptoms more precisely, a MK2 Xantia will have ABS, so it should not be possible to lock any of the wheels without the ABS kicking in. (and then how do you know it was a rear wheel that locked?)

dnsey · Post by **dnsey** » 18 Jun 2010, 18:07

the front two spheres look quite new

They usually do, as they live in a relatively clean, dry environment.
The best guide if in doubt, short of a proper pressure check, is to look for date codes

Dommo · Post by **Dommo** » 18 Jun 2010, 18:24

dnsey wrote:
the front two spheres look quite new
They usually do, as they live in a relatively clean, dry environment.
The best guide if in doubt, short of a proper pressure check, is to look for date codes

How old is 'too' old? My front corner spheres were made in 07 I believe, and they feel as though they could do with being changed?

Citroenmad · Post by **Citroenmad** » 18 Jun 2010, 18:27

Really sphere dates dont have much of an importance, as on the shelf they lose very little, if any, pressure. When fitted to the car they obviously do lose pressure.

Its often said that 3 years or 30K miles is a good time to swap/regas spheres.

A pressure check is the only real way to check a sphere, even very old spheres can be good ones.

The brake problem could well be nitrogen or air in the system, which does cause odd effects.

citronut · Post by **citronut** » 18 Jun 2010, 21:10

xantia_v6 wrote
"The brake balance is entirely controlled by the doseur valve"

that may be so but the rear suspension dose return via the doseur valve

regards malvolm

Post by **xantia_v6** » 18 Jun 2010, 21:22

citronut wrote:xantia_v6 wrote
"The brake balance is entirely controlled by the doseur valve"

that may be so but the rear suspension dose return via the doseur valve

regards malvolm

No argument with that, but the thread seemed to be going off on a wild goose chase...

I think the advice has to be to bleed the brakes and if the problem persistes, get a better description of the symptoms.