Xantia Softness

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skwuddles
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Xantia Softness

Post by skwuddles »

HI ,I've Just joined this forum,I've been looking at it as a guest for a few months .
I bought my first BX(auto) 6 years ago ,10 years old 51,000 genuine miles ,great car ,and have been addicted to Hyrdropnuematic suspension ever since .
I recently upgraded to a Xantia VSX 20.I auto,94 model 80,000 miles and only £800.,but I found that the suspension was not as soft as the BX. My local citroen mechanic ,told me that all Xantias,ride much "firmer" than BX's,( AND NOW THE GOOD NEWS <IF YOU WANT THAT SQUIGEY, SOFT, FLOATING ON AIR FEEL,) fit XM comfort spheres , I just had them fitted today and my car is like a magic carprt again !!!
AMTEX dont make comfort spheres for Xantias, but the XM spheres are perfecly OK and they're only £18.21 each from the wonderful Andyspares AKA GSF
Hope I've helped all the Xantia owners who want a softer ride ?
Float on , Love Skwuddles xxx
alexx
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Post by alexx »

Did you fit genuine XM spheres, or modified ones? And are they hydractive, or non-hydractive ?
Dave Burns
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Post by Dave Burns »

Hmm...just had a butchers at the sphere table and they look like the same ones to me, can't see much difference between the xm the xantia range of spheres for similar model types that would make alot of difference to the ride.
I would like to try a dose of CX spheres on a xantia though, 500/75/1.9 on the front would make a hell of a change, be like riding on a marshmallow, wonder what daimeter the strut pistons are compared to a xantia.
Dave
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AndersDK
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Post by AndersDK »

Dave -
Remember - the CX does not have "struts" [;)]
The CX have cylinders and upper/lower triangle arms at front - like the GS.
The cylinder inner diamter I believe is 32mm ?? - could be 34 or 35mm though. It's the same as used on rear on GS/CX/BX/Xantia/XM - slightly different outer design as pr mounting method differences - and later HA systems.
The front "strut" models have much smaller inner dia (20mm ??) in the actuation cylinder - which means a lower flow rate in/out the cylinder during suspension work for starters.
But the GS/CX front cylinder is fitted at approx 3/4 in on the arm related to the wheel - thus you only have approx 3/4 the wheel bounce here.
The strut is directly following the wheel bounce.
So wether the one type cylinder has higher flow rate in/out the sphere orifice related to the other type - during normal suspension work - I'm not really sure.
But the rule of thumb using old model spec spheres for softer suspension should still apply - as newer models always seems to be "uprated" in sphere damping - for vehicle stability at speeds.
alexx
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Post by alexx »

Yesterday I visited my mechanic to refill the spheres (we did only accumulator, because fronts were almost like new). While he was refilling may accu sphere, I checked various refilled spheres on the desk.
So I compared XM and Xantia front spheres. I noticed several things:
- discs around central bore seem to be the same on hydractive and non-hydractive spheres for the same car, only central bore is smaller on HA ones
- Xantia spheres have considerably thicker discs around the central bore. According to info from one Jpn site, XM spheres have two A-type (0.22 mm) discs, while Xantia spheres have three A-type and one U-type (0.165 mm). From what I saw, I think those data are correct. These outer discs control damping during extraction, so it's almost 2 times higher on Xantia spheres. Inner discs, controlling damping during compression, of course wasn't visible. According to mentioned site, damping during compression is similar in XM and Xantia spheres
But according to same site, XM rear spheres have three A-type discs inside and outside, while Xantia spheres have two A-type discs inside and three A-type outside. But, on Xantia they are maybe mounted with higher preload, so it's hard to say are they 'stiffer' or not.
Xantia can be quite uncomfortable on short road waves, like conventionally sprunged cars, compared to BX I owned before, with GS spheres on. It's obviously because these discs are thicker. But, on some surfaces, where BX was shaking my teeth (sharp bumps, gravel etc), Xantia is more comfortable and suspension noise is lower. I believe it's because main bore between damper valve and diaphragm is larger.
My front spheres have specified central bore 1.5 mm, but I think it was somewhere around 1.3. For rear spheres, 1.2 mm is specified, but it is actually around 1.0 mm. GS spheres, at least those from my father's garage, have also central bores about this size. Can't understand why this difference between specification and actual diameter. Only CX front spheres have really big central bores, they could be around 1.9 mm, as specified
CX front suspension cylinders have diameter 35 mm and are connected at about 40% of arm length, making their equivalent diameter 22.1 mm, if they were attached at the end. On GS, they are attached at about 33%, so their eq. diameter is 20.2 mm. BX struts have 22 mm piston diameter, XM struts 22 or 25 mm, depending on the model (Xantia probably similar). On higher diameter of the strut, same spheres will provide higher damping.
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Post by DoubleChevron »

Hi Guys,
as stolen from the QA forum, this appears to be quite a good explanation. I'm not the authur and certainly can't guarantee it's accuracy.
---------------------------------------------------------------------
So, we have different theories here.
As Anders said, higher pressure in the sphere means lower spring rate, which is in proportion with:
m * m / (V * p)
where:
m .. mass supported by the strut
V .. volume of the sphere
p .. 'nominal' pressure of the sphere
It's important to know that 'nominal' pressure of the sphere is not 'working' pressure of the sphere. When system is pressurised, gas in the sphere gets compressed until pressure is high enough to support the car. If nominal pressure is lower, gas will be compressed to smaller volume, and we'll have stiffer spring.
Anyway, several bar more or less makes almost no difference in ride. Damper on the sphere is much more important. As I explained several times on different forums, it's not only central bore. Characteristics of the damper are determined by quite a number of different things:
- central bore diameter: low speed damping (low vertical speed of the suspension, not horizontal speed of the car)
- surrounding 8 bores, inner and outer discs covering them: medium speed damping in both directions (compression, extraction)
- bore above the diaphragm: high speed damping
- diameter of the hydraulic cylinder and the way how it's connected to suspension arm
Drilling the central bore will bring only minor and questionable improvements in ride comfort, but much bigger degradation of roadholding.
In general, suspension of newer citroen vehicles (Xantia, C5), in comparison with older, have:
- higher spring rate
- slightly higher low speed damping, to achieve similar eigen frequeny of the car - around 1 Hz. This is also the reason why they don't 'float' as much as older ones
- slightly higher medium speed damping, to achieve better roadholding, but - damping during extension is higher than damping during compression, like in other conventional cars (in older citroens it was 1:1). Downside - short roadwaves are felt more than on older citroens, sometimes like in the car with conventional suspension
- lower high speed damping, to improve comfort and lower the suspension noise on rough surface, sharp bumps etc
- soft polyurethane bump stops instead of hard rubber ones
- slightly smaller suspension travel
So, this subject is rather complex, isn't it ?
---------------------------------------------------------------------
seeya,
Shane L.
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AndersDK
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Post by AndersDK »

[:)][8D]
alexx
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Post by alexx »

It's accurate, as I wrote that post [8D]
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Post by David W »

I drive quite a few cars every week, including various BX/ZX/Xantia models.
To be honest I'm always amazed when I find folks searching for an improvement to the Xantia suspension.
My own car is a 1993 1.9TD on 14" wheels and I do find this particular early car on the smaller wheels is the best riding Xantia of all. If you take one of these with no arm/strut faults and new spheres it is superior in comfort to both the BX and ZX...as well as many other large and prestige cars.
We live in the rural Fens with some of the worse undulating roads in the country. A Xantia is possibly the best car I've ever driven on such roads for keeping the wheels in contact with the tarmac while insulating the occupants from the bumps.
I do accept that the DS and CX models mostly had an apparently "better" more floaty ride but they were larger cars from a different era with different priorities.
David
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Post by Dave Burns »

I had a 94D and it was a softie compared to the 97TD I've got now, I know the D has higher pressure spheres and slightly larger damper orrifice than the TD, so I put a set of them on a family members 98TD, it made it softer than it was but nothing like my old D.
I particularly want to try some larger capacity and higher pressure spheres to see if I can make the car go over speed bumps without being chucked about so much or having to slow to a snails pace, If I want to miss the traffic and get off the main drag I have to go over these bloody things.
Whats the likelyhood of obtaining recently manufactured spheres for a CX given that they are now as common as hens teeth.
Dave
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Post by David W »

Dave,
Speed bumps...now there's the funny thing. My Xantia will take those at any speed up to 30mph with just a muted "bonk" from the suspension.
I wonder why these earlier cars seem better then? Currently I regularly drive two early cars and six post 1996 models. All the later cars have exactly the same firm feel.
As a matter of interest tyres can make a huge difference to the lower speed town bump absorbtion. My own car has reached its current peak in ride quality after fitting a set of Goodyear Venturas. They are those weird looking ones with more channels than rubber. The reduction in slow speed bump thump when these were fitted was incredible.
The previous tyres were one of the current Michelins, those were noticeably harsher than the earlier type Michelin fitted when I bought the car.
David
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Post by Dave Burns »

David, snap, I've been on 205/60/15 Venturas for the last three years, be a sad day when they stop knocking them out, don't know what I'd put on next, it wont be Michelin thats for sure, not after my experience with Energies, what sh!te they were.
But yes I certainly agree the Goodyears make the car alot nicer and it goes round corners in the wet better than ever, very reassured.
Dave
skwuddles
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Post by skwuddles »

Hi All
I started this topic , and it became very technical,I know, alot of you guys are into the precise ,(Diameter,capacity ,etc of spheres).
I'm not , all I want is a nice comfotable ,soft ride in my Xantia , And, since the XM comfort spheres were fitted yesterday , I have been on a nice 100 mile jaunt through the surrey,east and west sussex back roads,and I have found that the car floats along beautifully.
I thought that sharp twisty bends would be a problem with the softer suspension, but it wasn't ,I thought I might need to put it in hydractive mode , but I tried it once and the suspension stiffened up to slightly harder than nomal mode !! (ie ...without comfort spheres)I understand, that Xantias with hydractive ,and (ECU), read the road!! , and the amount you (brake , turn , accelerate,etc')is fed back to the computer ,so the suspension will never be too soft according to road conditions !!
But basically , the 100 mile drive I did today was far more comfortable ,with the comfort spheres , than with the original Xantia ones !!
PS Dont ask me any technical questions !!!!
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Post by David W »

Fair point about the non-tech approach Graham...you wanted a result and you are happy you've found it. However some of the background info sharing/discussion is why this forum can be so good at getting to the bottom of a difficult problem.
Can I ask if you had new standard (ie correct for your car) spheres fitted after buying the car or did you just get it changed from the original spheres to the advised comfort ones?
David
skwuddles
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Post by skwuddles »

Hi D.J.
When I bought the car ,back in November , I went through all the service history , and noticed that new (xantia) spheres were fitted only 2000 miles ago ![:)]
I have since done 1000 miles , and the (xantia) spheres , were working fine (as they should be at that mileage ), but as I thought the ride so hard,"compared to my BX" That I would try the XM comforts ,and as I said , It now rides like a BX .[:D]
As for the technical side of the forum, I do appreciate it ,very much ,as i can learn an awful amount about my car , as there is always something going wrong !!!!, [;)]
With time, and learning , I might be able to give some technical advice myself??[:)]
Regards Graham
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