Dumb idea..but here goes...

bxbodger · Post by **bxbodger** » 18 Oct 2004, 17:31

<blockquote id="quote">quote:<hr height="1" noshade id="quote">is the braking system connected to the suspension?<hr height="1" noshade id="quote"></blockquote id="quote">
The answer is yes-if, however, your knowledge of the car is so limited that you were not aware of this I would suggest leaving the brakes well alone-do not touch!!!Any alternative calippers you may be thinking of fitting MUST be LHM compatible.
Basically, how it all works is that theres a big green tank of LHM ( you may have notced there's no seperate brake reservoir or sevo), and a hydraulic pump- this pump runs off the engine and puts the LHM into the hydraulic suspension, braking, and steering circuits. There's a further (accumulator) sphere on the front of the engine that actually applies the operating pressure-simply put, when you put your foot on the brake the fluid is admitted to the callipers and the accumulator sphere applies the pressure.

406 V6 · Post by **406 V6** » 18 Oct 2004, 18:02

For what i've read i this forum and other Cit tech docs and stuff, the system will itself "bleed" the forming gases from the brakes, by simply compensating with more pressure.
Am i right guys?
Hum, i think ffelan should take a look at the tramontana site to learn a bit about our citroëns

. You won't be dissapointed!
Cheers!

jeremy · Post by **jeremy** » 18 Oct 2004, 18:14

As Bodger says the brake valve is simply an on off tap, not a pump as on normal systems. LHM itself has a high boiling point especially when new so the answer is to bleed the old fluid out and make sure that the calipers and preferably the rest of the system is filled with new fluid. Instructions on bleeding can be found by a search.
If fluid boils with luck it will cool and condense and air shouldn't get into the system. While in its vapour stage it will be compressible and I'd have thought a mechanical pump and a good accumulator was better at compressing the mix than a small capicity foot operated pump.
As Xantai's have only a 2 piston pump for brakes and suspension a good accumulator will be essential.
jeremy

AndersDK · Post by **AndersDK** » 18 Oct 2004, 18:22

ff -
You ned to know at least the basics on the LHM hydraulic system on a Xantia.
As a primer : the LHM hydraulic oil has way different properties than a DOT5 brake fluid. You may say in some aspects it's "better" - but above all : it's way different.
Try this for the LHM hydraulic oil basics : LHM fluid service
For the suspension & brake systems, you should at least skim this document : Gabor's Citroen guide
I agree with others that you can/must not go use any other brake parts - other than performance discs and pads.
The generic brakes on a Xantia are indeed very powerfull - as they are based on the system's hydraulic pressure - not your foot pressure. This means that Citroen in a way has designed/provided large over capacity as to never have complains from lack of brake power in their hydraulic cars.
To put it in other words : Citroen designed a very weird (& annoying) "spongy spring" into the bralke pedal - to give it a more "normal" feeling.
If not for this spring - you would need at least a couple of weeks learning how to dose the brakes. They would literally lock the wheels if you by mistake hit the brake pedal.

ffelan · Post by **ffelan** » 18 Oct 2004, 18:59

cheers guys...
will do more reading...
tbh i had been told about brakes / susp / steering all using same reserve but it hadnt clicked..... at least by the sound of the lhm guide boiling fluid should not be a prob...
as was not changing calipers then that is no prob either.. bigger discs and pad compound will give better stopping power... and will use height adjusters to run lower... is there any way of upping the system pressure to get harder ride at lower height... or do i just not bother renewing my spheres that i suspect are in need of changing?

AndersDK · Post by **AndersDK** » 18 Oct 2004, 19:13

OK Paul [:)]
The suspension becomes firmer as the spheres "wears" (read : the spheres looses gas pressure over the time).
This is the common annoyance with hydraulic Citroens.
However in your case : it's a gift from heaven [8D]
The lower the gas pressure in the spheres - the harder/firmer the suspension. Until completely "flat" spheres that will rattle out your teeth - like in a gocart.
And the car would pretty much also handle like a gocart.
Note that the "shocker effect" is still build into the spheres as a restrictor valve - exactly like in an oil shocker.
The sphere pressure then roughly determines the "lenght/stiffness" of the springs.
As for leaning/cornering - you still have the good old anti-roll bar to opt on.

AndersDK · Post by **AndersDK** » 18 Oct 2004, 19:25

BTW : some good graphics on the Citroen principles :
http://web.actwin.com/toaph/citroen/work/work.html
Especially this one : http://web.actwin.com/toaph/citroen/work/shock.html

ffelan · Post by **ffelan** » 18 Oct 2004, 21:01

ok dumb question number 689:
brakes in terms of discs / pads.. std is 268mm ? or 247mm? how much of the disc/pad/carrier/caliper is common across other models/peugeot?
can i fit larger discs with a diff caliper carrier? or do i need to be more extreme.

Post by **Jon** » 18 Oct 2004, 21:04

What sort of Xantia is it?
Smallest Xantia Front discs are 266mm, then you get 283mm on the 2.0 16v and Estates, largest are 288mm on the V6 and HDi 110BHP. You need the correct calipers to suit if you are going up a disc size.

AndersDK · Post by **AndersDK** » 18 Oct 2004, 21:09

I'm wondering if it is a Xantia after all ? [:)]
It's not really a Xsara - or ZX ??

ffelan · Post by **ffelan** » 18 Oct 2004, 21:28

xantia 1.8 16v sx so assume 266mm.. anybody have a part number for ferodo DS2500/DS3000 pads for this? how difficult would it be to add the 283mm?
http://www.griff-eng.co.uk/brakes.htm
would this fit - works on saxo 106 205 206 306 etc? then i can order 306 gti6 discs from GSF and really stop?

Kowalski · Post by **Kowalski** » 18 Oct 2004, 22:10

If you get the correct calipers for your Xantia you'll be able to swap calipers, pads and discs without having to mess about with adapter plates / brakets etc.

Homer · Post by **Homer** » 18 Oct 2004, 23:15

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

xantia 1.8 16v sx so assume 266mm.. anybody have a part number for ferodo DS2500/DS3000 pads for this? how difficult would it be to add the 283mm? <hr height="1" noshade id="quote"></blockquote id="quote">
If you get the right Xantia caliper it should bolt straight on.
<blockquote id="quote">quote:<hr height="1" noshade id="quote">
http://www.griff-eng.co.uk/brakes.htm
would this fit - works on saxo 106 205 206 306 etc? then i can order 306 gti6 discs from GSF and really stop?
<hr height="1" noshade id="quote"></blockquote id="quote">
Very very unlikely it will fit a Xantia.
Oh, and while you are on your track day, don't try anything fancy with the handbrake. (i.e. handbrake turn)[;)]

Post by **martyhopkirk** » 18 Oct 2004, 23:43

Would it be totally impossible / unrelistic to disconnect the spheres and fit shocks with coil over springs? (or even lenghths of scaffold for that totally daft / dangerous/ teeth jarring ride?)
Once remember in 2cv6 racing somone pouring something (sure it was cement) into the springs to stiffen the car up.
Or perhaps i dreamed that bit?

CommY · Post by **CommY** » 18 Oct 2004, 23:44

Could you not run the LHM through an oil coller to keep the temp down. Don't know if a standard oil cooler could handle the pressure on the outward leg but if you cooled the returning oil (which would be the hot stuff anyway) this should be OK!!
It's a sure heavy track day car, my Alfa Sud runs about 170BHP (at the flywheel) but only weighs 790kg that means to keep up with my love you'd be needing around 300bhp.