Me and my C5 - a real story

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DoubleChevron
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Post by DoubleChevron »

Hi Guys,
the rear H/A sphere on my Xantia VSX was dead, I have replaced it with a standard accumulator sphere. The car is now as soft as a marshmello in the back (infact a little to soft probably). I think playing with the suspension sphere valves is the wrong approach, rather you need to tinker with the H/A bore size to get the car softer in soft mode. When the center sphere is isolated (hard mode) you certainly want nothing changed (which is what you are changing when you modify the wheel spheres). !!
If outright ride comfort is what is required, a DS is the only way to go. They are easy to get in and out of (big doors, high seats) and I will have a very nice DS oneday ... when the finances and time allows me to finish the DS21 restorer I bought a few years back... (after I finish the CX C-matic restorer I have and have finished my mothers 2cv and ... etc ...).
seeya,
Shane L.
Doc
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Post by Doc »

I bought my XM because 2 years ago I was recovering from a spine operation to remove a tumour. At first the little blighter was giving symptoms similar to a herniated disc, but then similarities stopped as pain increased "off the scale". To cut a long story short, two MRI scans and a 7 hour op later and the offending thing was removed successfully. I found the XM helped a lot. My previous car was a Rover 216 TC GTi and would make driving over a cigarette paper feel like hitting a rock. Not good for bad backs! The XM rides smoothly on motorways but on any other type of road it tends to transmit every bump and lump in the road. Though it's not harsh, one tends to 'hear' the movement rather than feel it. Maybe the front spheres are on the way out. If I had the money I would go for a DS or if I was brave - a CX Safari. Their front wishbone suspension set up rides a lot smoother. I know that this is a technical forum and not a medical forum but if anyone out there is suffering from bad back pain keep pestering your GP. Don't let him/her fob you off with painkillers or instructions of 'bedrest' If I had listened to my first doctor, I would now be in a wheel-chair.
Andrew 'Doc' Pullen
alexx
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Post by alexx »

Francisco,
You can find these and other useful data in various documents on Yahoo C5-L forum. You must subscribe and go to download section.
Image
Image
As you can see, models with 136 HP and more have "real" hydroactive suspension (HA3+), with additional middle spheres, so fitting hydractive (HA3+) corner spheres to nonhydractive (HA3) car is not an option. Note that data for rear spheres are wrong - HA3 and HA3+ spheres mixed up. HA3 spheres should be 31 bar, HA3+ spheres 25 bar.
These spheres are not easily refillable, unless you drill the hole on the top, wind the threads and fit the screw.
Several bar more in spheres will lower the spring rate, but this will bring only slight improvement on long road waves (highways etc), where hydropneumatic suspension is already much better than the conventional one. Also, even this is questionable on C5, because of bump stops. On short bumps, there won't be any difference - these are taken almost entirely by the damper valves. It can be even worse - suspension arms will be hitting bump stops more frequently. Note that spring rates on the C5 are still about half of that on sprunged cars.
I refilled rear spheres on BX and Xantia to slightly higher pressure, but ride comfort isn't better, only the car floats more, which is not the same thing.
Patxi
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Post by Patxi »

Alexx,
Where is that data in the C5 list? I'm a subscriber there (mail:freespeedpro@....) and all i could find was the tech documents from citroen for training purposes on the files section...
And what do the 2 values (for instance, 1.9/1.3) mean? main hole bore and disks bore?
Doc, pain killers are no good for me. For instance, Voltaren (don't know if this is a universal name) only works once, and for around 3 hours. The only thing that it makes (besides cutting down pain a bit) is to hit my stomach ulcer. For a young fellow, i have a lot of things!
I'll try to check out a '73 DS. it's around 200kms away, but my Pug will help me out... God!, auto gearboxes are absolutely faaaabulous!
alexx
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Post by alexx »

Well, I didn't visit that forum for months (forgot may username/pwd). It was in files section, file name was Presentation_C5.pdf. I can post it to you if you want.
1.3 mm is probably diameter of the middle part of the central bore - it's about that size on Xantia and GS spheres also. 1.9 mm is probably diameter of the beginning and end of the bore (look at the picture of the sphere). On GS spheres it was, I think, 3-4 mm, on Xantia spheres whole bore is about 1.3 mm in diameter.
Couldn't find specified diameter 1.8 mm for GS spheres anywhere on the sphere, neither 1.5 for Xantia spheres.
Bores under discs are bigger - their diameter is 3-4 mm.
In fact, central bore diameter is useless data - complete diagram - suspension speed (in both directions) vs. damping force is needed to tell the difference between spheres, but there's no such data outside the factory
lhm_leak
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Post by lhm_leak »

I didn't realise there were so many of us in the "bad back brigade" ! I'm afraid that I'm yet another of them - and I do wonder if letting myself be gutted like a fish was worth it in the long run, because three years later I still can't feel the back of my right leg and still have lots of pain there. Tried most things (surgery was a last resort) but to no avail. Peter, what *is* this technique you use, and would it be any use to me?
Back (!) to the cars - Citroens seem to have got much harsher as the years progress, but they're still more comfortable than anything else, in my opinion. I sometimes think my Xantia has gone rock solid but it only takes a drive in the Cavalier to get a sense of perspective!
Stu.
Patxi
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Post by Patxi »

Maybe we should create a sub-forum in this one for the Bad Back Brigade, the 3 B's! What do you say guys? [:D]
I've so many times, with pain, wished for being openned up! The sciatic is getting down my nerves (oh!, did i tell you i also have a huge depression?).
Now, for the subject in question:
I'm gonna try to buy the 1.8L spheres (200 euro each). Or enlarging the bore to 1.4mm - cheaper. Last night i went out for dinner eith my Mom, tryed some nasty tarmac. At intermediate height (4cm higher than normal) it seemed smoother, while trying to keep the same speed for the test. On the other way, the car, for instance, small cuts on the tarmac for speed sensors (around 5mm deep x 15mm~20mm wide), transmits them very nicely (it actually amplifies their size!). Ok, the ride, as i told before, is still, in some cases, smoother than my Pug. I will try to cut a bit on the bump stops. Citroën refuses to reprogram a new height setting for normal handling, like Alexx sugested (the only way to change height on this baby).
Doc, what you said is scaring me, as, in last year's MRI, the disc thcikness isn't smaller near the herniated part...
alexx
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Post by alexx »

Francisco, as you wish ... I wouldn't do that, but it's your car.
If you make these modifications, can you post us some photos of sphere damper valves, to se how different they are from 'LMH' spheres ?
Patxi
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Post by Patxi »

Alexx, i will post the photos.
Is the damper set detachable from the sphere? If so, how do i remove it?
Bye!
alexx
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Post by alexx »

Damper valve is pressed or winded into sphere and isn't easily removable.
You can find some photos on these links
http://homepage1.nifty.com/wasenobu/tamaa.htm
http://homepage1.nifty.com/wasenobu/tamab.htm
http://homepage1.nifty.com/wasenobu/tamac.htm
http://homepage1.nifty.com/wasenobu/tamad.htm
http://homepage1.nifty.com/wasenobu/tamae.htm
http://homepage1.nifty.com/wasenobu/tamaf.htm
http://homepage1.nifty.com/wasenobu/tamag.htm
It's a Jpn site, use some internet translator. The guy did some experiments altering characteristics of damper valve, by altering diameter of it's bores and quantity of discs. Only, it's not clear to me what was the result ...
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