Xantia Trait ?

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lexi
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Xantia Trait ?

Post by lexi »

The 3 Xantias I've had all do this and it's annoying. What is it?

When you come to a halt at lights and are sitting with foot on brake............the suspension rises! I probably notice it more on V6 auto as foot is on brake more. It feel like just the rear rises.

So............when this happens and you take off. Car is not technically at proper height? It seems to settle obviously but how long it takes I'm not sure.

Does this mean that on the move car could be risng when braking heavily?
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Post by xantia_v6 »

My experience of Hydroactive Xantias is that the phenomenon of the rear end rising while sat at the lights is caused by (or can be overcome by) driving style.

If you come to a halt gently, or momentarily release the brakes after stopping, so that the suspension "unwinds", the height then seems to stay more stable.

On some cars (I think depending on the brake pad material), it you sit with just minimal pressure on the brake pedal, the front of the car tries to creep forward, but the rear wheels are held by the brakes, and this can cause the suspension to "wind up" again and the height to rise.

So try stopping gently, but then hold the brakes firmly (or use the handbrake).
lexi
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Post by lexi »

Exactly my driving style V6. Light brake at standstill and handbrake on at lights. It`s trying to explain that to my lovely Wife and Daughter who use the car occasionaly :lol:
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Post by Xaccers »

why are you pretending you're a bmw driver?
use the handbrake and stop blinding the poor sods behind you!

the rear brake hydraulics are linked to the rear suspension.
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Post by Dommo »

It's probably also to do with the trailing arm design, the trailing arm design means that when you brake the rear suspension sags, this along with using the suspension fluid for the brakes means the rear end sags when you brake so you don't get brake dive.

On a 306 like mine it does the same thing, if you pull the handbrake (which acts on the rear wheels on a 306) the rear end sags down quite a lot. So if you imagine pulling up to a standstill quite abruptly and keeping the brakes on, this means the suspension isn't allowed to rise back to where it should, so the system thinks more weight is added in the back and therefore raises the suspension to compensate.
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Post by Old-Guy »

Regardless of being considerate to the driver behind, sitting with your foot on the brake pedal is potentially fatal and also damages the discs:

- If you get rear-ended, you will be thrown backwards, jerking your foot off the pedal so your car get punted forwards a lot further than if the hand-brake had been on. At a pedestrian crossing, this could easily be the difference between hitting several people and just giving them a bad fright. At a junction, it could mean being T-boned by a truck doing 50+! In such a non-accidental collision you could (if still alive!) be found to have contributed to the severity.

- Holding hot pads on hot, static, discs for more than a few seconds creates a hot-spot on each rapidly cooling disc - the major cause of warped discs.

Look at any traffic queue; 9 out of 10 drivers are sitting there with brake lights on. Be a better driver and put the handbrake on. Maybe you'll save a life one day - perhaps even your own?

Lexi, have you tried the first argument on your ladies?
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Post by Gingerposer »

Thinking about the hotspots issue, is this also happening when the handbrake is applied?

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Post by lexi »

Lexi, have you tried the first argument on your ladies

Wont work :lol:

Well aware guys of Heat issues with clamping pads to brakes etc. My xantia starts rising within seconds anyway. Yes Dommo my old ZX was like that too.

Ijust get the impression that V6 is going up sooner than my other 2 Xantia.........I think the pump could be higher pressure and have this effect?

Point being missed is that this is an auto and anyone who uses an auto uses brakes more anyway.....first thing you do when moving auto lever is clamp footbrake........it`s a safety thing and anyone taught to drive one will have had this drummed into them....

It`s not an issue for me really but just when you give someone the car you have to point out to them.

I can honestly say I`ve never driven a BMW.....what like is it Xac? 8-)

A bit like my old Locost 7 but with a house thrown on top? :lol:
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Post by Xaccers »

lexi wrote: I can honestly say I`ve never driven a BMW.....what like is it Xac? 8-)
had to drive one once, diesel auto, gutless with a 5 second lag between putting my foot down and the car responding.
It did have a handbrake, which being a French car driver I had no problem using, so I don't know why bmw drivers have such difficulty finding it.
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Post by Old-Guy »

Gingerposer wrote:Thinking about the hotspots issue, is this also happening when the handbrake is applied?
:oops: :oops: :oops: In a word YES - I forgot Xantia handbrakes operate on front discs! :roll:
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Post by Gingerposer »

I wonder if it's likely to cause problems then, would there be any way of avoiding the issue by modifying driving style or something else?
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Post by lexi »

Does this mean that on the move car could be risng when braking heavily
We never tackled that part.

On the Mot ramp I notice that a Xantia will rise on the rear brake test........sometimes it jumps as brakes are applied on and off. This may be accentuated by the Cadence Braking effect of ABS. The last time my Mot man commented on it and said a lot of them do that.
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Post by xantia_v6 »

lexi wrote:
Does this mean that on the move car could be risng when braking heavily
We never tackled that part.

On the Mot ramp I notice that a Xantia will rise on the rear brake test........sometimes it jumps as brakes are applied on and off. This may be accentuated by the Cadence Braking effect of ABS. The last time my Mot man commented on it and said a lot of them do that.
At the front end, the suspension geometry is arranged so that the natural dip of the front under braking is counteracted by the braking torque trying to raise the front suspension (so called anti-dive geometry). The Xantia rear suspension layout does not allow for such tweaks, but the reaction torque from the rear brakes does tend to wind up the trailing arm (where this thread began!). This is more pronounced on a hydroactive car in soft mode, and one of the reasons the suspension switches to hard mode on heavy braking.
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Post by lexi »

Well that`s interesting V6.

70% braking on fronts anyway and I've always found Xantia brakes superb . I check them often on my friends Mot equipment and find the percentage efficiency rates are always very high
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Post by deian »

the xantia won't squat down that much under heavy braking at the rear, nor will it squat down if you pull the handbrake prematurely... the handbrake is on the front of a xantia because of the self levelling suspension, the zx and 306 do squat down noticeably but i haven't seen it happen to such an extent on any of my xantias.

i don't believe the back rising is supposed to happen by design, the 'rear circuit' is fed independently to the front, and the amount of braking you have on the rear discs is based on the weight in the back... so the back rising when you feed the brakes sounds like a fault with the anti-sink (or rear accumulator if you like) valve somewhere.

someone more knowledgeable will come along and explain in more detail i'm sure.
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