BX TZD turbo, front suspension ride quality

beano · Unread post by **beano** » 18 Jul 2004, 18:55

Not to sure if I have a problem with the front suspension ride quality, or not.
On normal roads at all speeds it seems Ok, but going over rumble strips or roads starting to break up, it feels like the car is falling apart.
The front suspension feels a bit hard compared to the rear when I push the corners down manually, but not sure if that’s because of the extra weight from the engine and transmission.
The car has done 189K and I have replaced the following suspension parts over the last 12 months, not all for this problem.
Front suspension
Reconditioned struts.
Spheres including Accumulator
Drop bars
New Michelin 165/70 R14’s
Rear suspension
Spheres
Hydraulic suspension units
Rear arm bearings
I have also flushed out the system with Hydra flush, measured the height and found the front to be about 10mm more than the spec recommends (I haven’t adjusted this yet, after hearing some of the saga’s about this so called easy adjustment, even Citroen told me not to bother).
The other point is that in the morning the rear of the car has dropped to its lowest level whilst the front is pretty much as I left it, but trying to push the front corners down does work so its not as if the front struts have seized.
Any body got any ides on this, as suspension ride is so subjective.

uhn113x · Unread post by **uhn113x** » 18 Jul 2004, 21:32

Hi
Is it making any noise at the front - if so, maybe one or both drop links have failed again? The spheres could have done as well. Have you tried Citaerobics? Tested the height correctors? Generally, any crud in LHM ends up in them after flushing.
I would not bother adjusting ride height for 10mm.
Which end of the car sinks first, or how long it takes to do so, has no signficance at all. The HP pump is capable of supplying much more output than the system requires.

DLM · Unread post by **DLM** » 19 Jul 2004, 04:50

If you use the (recommended) 400cc spheres for the Turbo, then you're condemning yourself to a harder ride, and Citroen BXs nearly always dislike a rough surface at slower speeds anyway.
Have you tried either or both of the internal/external strut lubrication methods found in previous posts?

beano · Unread post by **beano** » 19 Jul 2004, 22:57

DLM and UHN113X,
Thanks for the info. I have tried the Citaerobics and found no noticeable difference, but will search for details on internal/external strut lubrication and let you know the outcome.
Thanks again

ScottFromNZ · Unread post by **ScottFromNZ** » 20 Jul 2004, 05:12

This is interesting. I have not been overly inpressed with the front ride quality of my BX TZD Turbo, despite new spheres and strut lubrication. The strut lubrication made the front rise more smoothly though.
I have felt that the front absorbs medium to large bumps well but smaller bumps and corrogations in the road seem to judder through the front causing the dash to vibrate and rattle a bit. BUT over about 90 km/hr the ride seems to improve markedly.
Mind you I think that alot of the harshness through the front is heard rather than felt through the seat. I still find that in you get out of the Citroen and into another 'normal' car you realsie how well the Citroen rides.
I did not know that the Turbo models use a different sphere. What would be the effect of using a non-turbo sphere in the front of my car?

mark_sp · Unread post by **mark_sp** » 20 Jul 2004, 16:55

Scott
The softest damped spheres for the BX are the big volume spheres for the early 1.6 and 1.9 carb cars. You will achieve a much softer ride wit a pair fitted (providing the other suspension compenents are functioning reasonably well). A couple of points to bear in mind:
Don't fit the alternative spheres if you are a press on driver though as body roll increases and stability decreases.
I've owned both TRS and TZD BX's and while the TZD is noticably firmer than the TRS it's still a softer ride than any Xantia or XM despite what anyone else may say.
Mark

ScottFromNZ · Unread post by **ScottFromNZ** » 21 Jul 2004, 02:50

Thanks Mark. I will keep this in mind. Another question.
As the spheres slowly lose pressure over a year or three, does the ride get softer or harder. I know that when the spheres are flat the ride is hard, but what about when they are, say, at half pressure?
Also, on a car that does not do many miles per year, will the spheres stay pressurised more years than on a car that does, say, 15,000 miles per year?

alexx · Unread post by **alexx** » 21 Jul 2004, 12:20

Well ...
500 ccm spheres won't improve the ride over small and sharp bumps (I had BX16 with those spheres), only the car will float more. It's because only central bore on the damper valve, which is responsible for 'floating', is a bit larger, while other parts of the valve, responsible for taking sharp bumps, seem to be the same on all BX front spheres except those for BX16v. I finally ended up with GS spheres (also 400 ccm), which offered smoother ride. Rough ride is partially caused by spheres - because of low spring rate, damper valve must strongly resists to quick suspension movement, and partially by worn suspension struts (their slide bearings).
Larger spheres won't affect body roll anyway, because LHM flows freely from left to right suspension cylinders - only thing keeping the hydropneumatic car leveled is roll-bar.
As spheres lose pressure, their spring rates rise and ride becomes a bit similar to that in conventional car with worn dampers - more bouncy. When they lose most of the gas, it becomes very hard.

mark_sp · Unread post by **mark_sp** » 21 Jul 2004, 14:31

Well despite all the technical conjecture I've done many thousand miles in a 1986 BX19 trs and then a TZD estate and I can only report as I experienced it. Both of these cars had the same wheels by the way.
The trs was a much smoother and softer ride all round, large or small bumps. It did not appear to float more than the tzd but it did have significantly more body roll, it was definately not a car to rush around twisty country roads in. The tzd was the opposite, it was so composed that it begged to be pushed ever harder. In the tzd I could not induce the same amount of body roll as the trs (maybe I didn't try hard enough).
Wish I still had the trs but after 15 years it had turned to rust below the waistline and the interior plastics had to be seen to be believed.
On the trs I had some recon spheres fitted by Westroen in 1995 and the ride quality was still good in 2001 when the car finally expired but the car had been laid up for a couple of years prior to that.
Mark

tomsheppard · Unread post by **tomsheppard** » 21 Jul 2004, 14:34

I'd definitely adjust the ride height to get the balance of the car right. If you are sorting out handling then you just have to, no matter what Citroen, the man in the pub or the angel Gabriel says. With the front 10mm overhigh, the roll centre of the front will be high and throw the front around. The rear roll centre will be low and ...Ugh! it doesn't bear thinking about. Why spend the money you have done and fail to set up a given spec to be within limits?

alexx · Unread post by **alexx** » 21 Jul 2004, 15:35

According to available data, BX TZD estate has thicker roll-bars than BX19 TRS (if non-estate), so roll stiffness is about 35% higher, while the weight of the car + load isn't that higher, that could be an explanation ...

mark_sp · Unread post by **mark_sp** » 21 Jul 2004, 16:51

Yes
There really are too many variables:
elderly struts
different spheres
different anti-roll bars
ride height
tyres
then of course individual perception.
Digressing slightly I've noticed something relevant to ride quality on my Xantia tyres. The car had cheapo Tigars fitted all round when I bought it, earlier in the year I fitted a pair of Michelins at the front. Although the Michelins are the same size as the Tigars to increase the pressure by a given amount requires more pumps on my foot pump for the Michelins than the Tigars, I'll do a proper measure next time.
Mark

tomsheppard · Unread post by **tomsheppard** » 21 Jul 2004, 16:56

suggesting that the Michelins have a greater internal volume = softer ride and they have more give in the sidewalls?

Unread post by **alan s** » 21 Jul 2004, 17:30

Don't talk to me about BX suspensions; I just caught myself a beauty.
Car was laid up for a while and when it went back on the road it felt like a dray.
Checked, all spheres felt hard as rocks so whipped them off & had tested.
One front one was blown. Beauty; found it. Wrong!!
Regassed another front sphere and two sets of rears. Rear was still stiff; changed to second set, softer but still not right. Jack car up & check for knock knees / \ no sign. No noises either; bummer.[V]
Drove into property today and hear almighty crash from rear; seems I had a rear swing arm bearing partially siezed. $#!+ of a job, but at least I know where the problem is now, so off to get a couple of bearings in the morning and see what that does; stay tuned.
Alan S

beano · Unread post by **beano** » 24 Jul 2004, 17:40

As suggested carried out the strut internal lubrication and it has made quite a differance especilly on the road but still not what I consider ideal, (again its all subjective). I will try Tom's suggestion of correcting the height and put it back into spec, but before I do that can anybody advice me if is this adjustment is staight forward and whether any precautions need to be taken beyond making sure you'v plenty of room between you and the car at its lowest height setting.