Ride quality...is it my imagination....

[Peter.N.]

If you increase the sprung to unsprung weight ratio it will always improve the ride because you don't get the 'tail wagging the dog' effect which is why things like Rolls Royces ride so well as will reducing the weight of the wheels.

Some years ago I drove my XM estate back from Newcastle with a 2.1 td engine and gearbox in the back and stopped off in Derby and picked up a Ford 1800 diesel for my son, the ride coming home was superb, performance wasn't very good though.

Peter

[GiveMeABreak]

If I'm honest the older C5s (MKI & II) were almost the same - a good load in the boot and they rode so much better (a very faint, soft waft). Neither my MK I SX and MK II Exclusive had Hydractive 3+ Suspension - so no centre spheres. So unless the pressures were way different, you would expect an additional 3 spheres on the X7 to have a softer ride, when in fact it seems to be harder - unless with the aforementioned loading.

I do often wonder if this could be one of the reasons why they have abandoned Hydropneumatic Suspension... Has it been over-engineered to conform to what is perceived by the masses as a 'normal' ride, getting firmer and firmer in each incarnation and in so doing, there is now so little difference in ride to that of a normally sprung car? Obviously self - levelling and auto adaptive properties aside.

It did all change for me when I moved from my ailing CX to my first XM. I loved the XM as a looker - the styling was very distinct and it looked truly unique like many previous designs. But the ride - very different, too firm - so much so that after a few weeks of owning her, I went straight to my specialist mech and complained that the ride wasn't right. Too bumpy, too rigid over raised manhole covers. I had the spheres replaced and the system flushed and bled. No real difference - kept telling myself it was just me and that I'd get used to it - but no, wasn't happy at all. Went back 6 months later and had the lot replaced with comfort spheres - as my mech had replaced all of his spheres on the XM he owned that was a year older - now we were back on familiar territory, that floaty, wafty ride that was characteristic of hydraulic Citroens. Boot the accelerator and I felt the exhaust was going to leave a trail of sparks! Those were the days.

[white exec]

Interesting comparisons, Marc. Additional centre spheres should provide extra softness and 'give' (just as increasing the gas pressure in a sphere will), and offer larger wheel excursion, if the geometry of cylinders and everything else allows. This will be felt as beneficial on smooth but indulating roads, where any hpn Citroen should give a superlative ride, if everthing is in a good state.

Trouble is, this wonderful softness can be seemingly wiped out by the system having very small damping orifices, or stiff by-pass washers, in both the wheel spheres and centre hydractive block. The softness can only show itself on a slowly undulating road, when the fluid only needs to get past the dampers relatively slowly. What is nasty is the crashiness and thud of a ridged or broken road, when fluid needs to pass through the dampers suddenly and at speed.

Some damping is essential, to combat dive and squat. Non-sporty BX was superbly comfortable, even on broken surfaces, but was both long-travel suspension and gently damped. It could dive and squat easily, if you wanted it to. On a larger and heavier car, dive when braking, in particular, presumably needs a bit more control.

I recently drove our XM for a few days with a pair of Accumulator spheres on the front corners, as a temporary measure whie awaiting a couple of proper replacements. The Acc spheres were the same 450cc as the correct items, and gassed up to the correct 50 bar too. The only difference was they has no damping whatsoever. The ride was instructive: superbly smooth, even over ridges and lumps. Wafty? Hell, yes, to the point of seasickness, especially on gentle undulations on a motorway. Not nice, but at the other end of the suspension spectrum.

My understanding is that 'comfort' spheres, for corner use, tend to have larger capacity (500 or 450cc, depending on space available) and less damping. Only issue I can see would be the loss of rigidity when the system kicks into Firm mode, when sudden braking or a serious steering manoeuvre is needed, where the car is designed to become taut. For a large car like XM, this might not be a good idea. However, the usual answer to this is 'Well, I don't drive the car like that - my main requirement is comfort.' A very personal choice.

Marc, I think you are right about Citroen's relentless shift towards stiffer suspension. When floaty comfort was the order of the day, hpn suspension was in a class of its own, with even Rolls Royce making use of it. Right, too, about the gap between most recent hpn and steel having become so close that the bean-counters have predictably asked why bother? To my mind, many modern cars seem to have appallingly hard suspension, not helped by low-profile rubber and frequent over-inflation, designed to give a sporty drive on near-perfect tarmac.

As I've reported before, we've lost count of the number of friends and family who make repeated and appreciative comments about our XM's comfort, and compare it to what their much newer cars offer. Maybe decent comfort, like good quality audio, is something that can easily get sidelined and forgotten. Flat-screen tv's are another example, sold to many folk without any suggestion of enhancement. Remember Double Diamond and Watney's Red Barrel? That was a low-point too - so maybe there's hope for the future.

Back with Citroen, if Soft mode is uncomfortable, something needs looking at, assuming that the car isn't tripping unnecessarily into Firm. Firm needs to be just that - unless you opt otherwise - but in Soft, the ride ought to be as good as it gets.

[Peter.N.]

No two XMs seem to be the same as far as ride is concerned, I had comfort spheres on all my later ones which did improve the ride but still not like the CX of which I had three. A little while ago I drove a 2.5 td XM which I don't like much because of the difficulty at getting to everything under the bonnet and the virtual absence of spare parts plus the poorer economy compared with the 2.1, but the ride was superb, I don't know why but it was, I have never driven another XM like it.

It was loaned to my son by John from the XM forum and he said it was the best one he had ever driven, unfortunately its now sitting in the field with a leaking fuel pump but it was almost worth the 20 mpg to experience the ride

It is heavier but I wouldn't have thought enough to make that much. difference to the ride. I used to run my 2.1s with 30 psi in the tyres, that made quite a difference.

Peter

[GiveMeABreak]

Chris, I agree with what you say. Regarding the comfort spheres, absolutely correct. It effectively cancelled out any firmness and made no difference if manually switching to 'Sport' mode. The trade off was of course the cornering - which as expected would cause more leaning. Again, a personal choice, as where I live, decent (or sometimes any) tarmac is a luxury. We have to suffer golf-ball sized chipping-coated roads, potholes a la everywhere, twisted winding roads, dips, hills everywhere. Absolutely fine on straight roads though. After I had the comfort spheres I did enjoy the ride for a while, but unfortunately, some time later a bull got out from a local farm and took a fancy to my XM's bonnet - jumping full-on, legs sprawled across the bonnet and onto the windscreen with me inside! Cue a replacement car - a series 2 XM a while later and decided to leave the original spheres as they were and the same for my next one. I think this was mainly as I did need the firmness to kick in on these roads. So that was my brief flirt with comfort spheres.

I do get reminded every so often of comparatively how more comfortable the X7 is, after I have been in another conventional car, or our C3, where you tend to feel every pebble, so I quit moaning and tell myself how lucky I was to get one of the last hydropneumatic cars there will be! If I ever have to replace the X7 in the future, I don't know what I'll do, as this truly will be the end of an era for me, after having driven many other cars, but having only ever owned hydropneumatic Citroens myself from 16 years of age! I will probably have a look at a DS5 - as I love the interior styling - just a shame about the 'flinstone' quality ride.

[white exec]

Hi Peter,

Interesting comments. Listening to owners, it does seem that the 2.5, being S2, does offer a good degree of comfort and interior quietness - all that extra soundproofing! Did wonder whether the 2.5 engine was heavier than others, but it's only 10kg more than 2.1 manual - but 53kg more than turbo petrol (so says Haynes).

No two seem to be the same? I suppose with the sheer number of variables - models, tyres (and pressures), state of spheres, state of fluid (with or without air ingress), system pressure/Accumulator, and age and mileage - a bit like typewriters or even people.

Glad you enjoyed the 2.5 from John, but that mpg . . . dreadful! We've never had below 32 on ours, except when towing a caravan, when it dipped to 28ish. Last autumn, when we went from here to Scotland and back (5000km), it returned 43mpg. I think at near 20mpg I'd be having serious second thoughts as well!

[white exec]

Regarding the comfort spheres, absolutely correct. It effectively cancelled out any firmness and made no difference if manually switching to 'Sport' mode. The trade off was of course the cornering - which as expected would cause more leaning.

I have no practical experience of X7 (or any C5) suspension, so interesting to read what you say. Just been looking at the electrovalve and its twin spheres. Presumably these two just work as a pair (in parallel), each being 385cc/70bar.
If so (?) this is the equivalent of a 770/70 single sphere, and so ought to provide lots of resilience (= wheel movement) and lots of springing (70bar is a high-end figure). Would guess, then, that the ride in Soft ought to be really good - unless something else has been compromised . . . . . or the EV is fitted with two very small aperture dampers connecting the centre spheres to the wheel spheres/pistons.

That's a lot of centre sphere capacity, and pressure, there - so my thought is that it should offer some rather good performance. No previous HA Citroen had that much potential comfort available at rear centre!

On your knobbly tracks (we have rather a lot of those, too) presumably the suspension is remaining Soft (unless your rallye-ing down them), so if the ride is knobbly, then it must be down to (tyres and pressures aside) centre sphere damping (assuming centre spheres are aok).

As I said, I think Firm should be just that (taut). You can't look to Firm (i.e. wheel spheres alone) to provide comfort; it's there for stability and handling in semi-extremis. If knobbliness isn't mopped up in Soft mode, then any injection of extraSoftness should, I think, come from looking at the centre sphere(s), which actually provide the Soft mode.

I'd be tempted to try standard wheel spheres, but maybe fit a couple of 450/70 centre spheres (easily sourced and fitted), or - more likely to produce a change - swap the EV damper inserts for some others. (These can probably be fished out with valve in situ, by unscrewing the 10mm pipes and their unions.)

Maybe someone has data about Hydractive X7 suspension regulator (EV) apertures, so some others could be identified. I'm also assuming that X7 EV valves use the same 'new internal pipework' as the revised Xantia valves, with the advantages they bring. The number of externally connected pipes might give a clue.

[chinkostu]

I drove mine 5 up with 3 rather...generously sized people and their luggage and it actually made the ride worse, it seemed almost boaty and sea sicky. This was on the old spheres mind, but it didn't fill me with confidence!

As I've reported before, we've lost count of the number of friends and family who make repeated and appreciative comments about our XM's comfort, and compare it to what their much newer cars offer. Maybe decent comfort, like good quality audio, is something that can easily get sidelined and forgotten.

Likewise with myself, plenty of comments on the smoothness and the lovely soft seats, but it isn't like newer cars where the doors are 3 foot thick and akin to sitting in a bunker. Theres plenty of outside and engine noise in the Xantia which seems to belittle its great ride, where people can be complacent in driving a wooden countertop if it were quiet, people seem to have decided that cars are supposed to be stiff. Mine gets a bit jiggly over some surfaces at low speed but i've decided thats liveable as the ride when cruising is superb.

I did 220 odd miles in a lowered Saxo and it damn near killed me, I did twice that in the Xantia and was only really mentally fatigued!

[GiveMeABreak]

Hi Chris, just checking those specs. For the X7 Saloon and my engine type:

• Front Wheel Spheres have an MC identification (allocation code) and are 50 bar
• Rear Wheel Spheres are ME coded and are 40 Bar
• Front Stiffness Regulators Accumulator is coded KR and is 70 Bar
• Rear Stiffness Regulators Accumulator are coded GV and are 44 Bar each

I've put a few diags of the rear centre spheres below, but will look and see if I can find anything else.







I note also that it seems the 2 rear centre spheres are possibly dedicated to the left and right wheel spheres? - The piping seems to lead off directly from each centre sphere to each wheel sphere. It can be seen a little better from Julian Marsh's site here - and of course with the running gear from the C6, it does have a completely different setup that earlier C5s and earlier hydropneumatic systems:

http://www.citroenet.org.uk/passenger-c ... c5-13.html

[white exec]

I'm guessing that the two rear spheres do not connect to one wheel sphere each, but simply work together in tandem. The regulator valve is a single channel item (it only has one shuttle valve), and would need to make Softness available to both rear wheels simultaneously, so I can't see any advantage in having an "extra sphere" for each rear wheel. Mushroom spheres are also reduced volume (385cc iirc) compared to previous versions (450cc in this case), and it's possible that the decision was taken simply to double up in order to keep available volume high. The valve body looks just like the front one (single sphere), but with the added 2-sphere adaptor.

Sorry to get muddled on the centre sphere pressures - I was looking at Parts, which is hopelessly vague on C5 sphere specs. 2 x 44bar it is then, 70 at the front.

So, one possible way to get some extra Softness (for Soft setting) could be to fit a couple of front 70bar spheres to the back, and see what happens. More pressure = more springing. Unless you have spare spheres available, this is less easily done with the mushrooms, which lack the ability to add a re-gassing valve. If you have access to re-gassing kit, it might be easier to do it with some old-type spheres. (Make sure you remove the sphere to re-gas it, or ensure there is no hydraulic pressure acting on the sphere, or you get a false gas pressure figure.)

Hope you can find some susp.reg. damper data somewhere. For XM and Xantia, the damping figure is listed along with general sphere specs (eg 400/50/1.25) but for the centre spheres it is noted that the damper for these is built into the regulator valve body. Have looked at the corresponding C5 document, but on mine there is no mention of damping characteristics for any of the spheres. Progress!

[GiveMeABreak]

Indeed Chris, very hard to find any additional info and I've been looking for ages. That link to Julian's site may not work - I think our site is now converting some of the links to secure https settings, so if the target website is not using https it seems to throw a wobbly. I've encased it in a URL wrapper and this one seems to work:
http://www.citroenet.org.uk/passenger-c ... c5-13.html

[GiveMeABreak]

Chris - Just found this article - mainly to do with Hydractive 2 - you may already have this or something similar, but it's a 97 page document - and does contain some data that you might find useful. I've put it onto my storage account - let me know if it's not of interest and I'll unlink it.

https://mega.nz/#!38EUhZ5S!hH2squizCr4P ... SOiHW7DzLw

[white exec]

Thanks for posting that HA2 document, Marc. I already had a copy of it, but thanks, anyway. It relates mainly to Xantia (although not clearly saying so) but useful anyway.
I wonder what the source of some of these mega.nz..... documents is? The revised Xantia EV valve document came from a similar source. The title page, and usual Citroen headers/footers, are missing, so difficult to identify what publication they originally were, and difficult to search for any similar or later documents.

I did manage to get into Julian's pages, by the same means you did.

On sphere specs, it's annoying to find basic info like damping missing from the various documents. I guess so long as the part is identified, and orderable, that's all PSA now cares about. Never mind what its specs are. Heaven forbid that anyone should actually understand exactly what it is and how it could perform! OK, but this also makes it difficult to check out pattern part offerings, to make sure they exactly match OE. Perhaps that's the intention.

I think that when new industrial products are first launched, a lot of effort goes into making sure that field operatives know all the ins and outs of the product. This training is often done by the very folk who devised the product, and were responsible for field testing it and making sure it was successful. Thereafter, it all becomes a sales and marketing item, and the boffins move on to the next project. Maybe that's why H1 and H2 are so well documented, and then it starts to get difficult. Or maybe security around training and engineering documentation just got tighter!

[Peter.N.]

Hi Peter,

Interesting comments. Listening to owners, it does seem that the 2.5, being S2, does offer a good degree of comfort and interior quietness - all that extra soundproofing! Did wonder whether the 2.5 engine was heavier than others, but it's only 10kg more than 2.1 manual - but 53kg more than turbo petrol (so says Haynes).

No two seem to be the same? I suppose with the sheer number of variables - models, tyres (and pressures), state of spheres, state of fluid (with or without air ingress), system pressure/Accumulator, and age and mileage - a bit like typewriters or even people.

Glad you enjoyed the 2.5 from John, but that mpg . . . dreadful! We've never had below 32 on ours, except when towing a caravan, when it dipped to 28ish. Last autumn, when we went from here to Scotland and back (5000km), it returned 43mpg. I think at near 20mpg I'd be having serious second thoughts as well!

The 20mpg was tongue in cheek as most of the fuel was pouring out under the engine due to the leaking pump, they are not really as bad as that.

Peter

[GiveMeABreak]

Thanks for posting that HA2 document, Marc. I already had a copy of it, but thanks, anyway. It relates mainly to Xantia (although not clearly saying so) but useful anyway.
I wonder what the source of some of these mega.nz..... documents is? The revised Xantia EV valve document came from a similar source. The title page, and usual Citroen headers/footers, are missing, so difficult to identify what publication they originally were, and difficult to search for any similar or later documents.

I just located them from various sources over the years and bunged them into storage on my PC- 'just in case'. That Mega NZ is just where I have a hosting account to be able to securely upload documents and make them available Chris - it's where I loaded the Evolution document too, so that's where your remembering it from probably.

Regarding information - I think one of the issues is that a lot of 'paper' based bulletins and updates & technical briefings etc., started to 'online' from 2006 on. I have stuff about this time, but after that it's all gone into the ether - just like all the Diagbox bulletins seem to have dried up!