harsh potholes

[RobC]

hello again, while my mind was on the bx i thought of another issue.

my front spheres are faily new and very smooth on the motorway, over speed humps, etc.

however on normal height the car really gets upset with pot holes - sometimes i'm amazed the whole car hasn't fallen apart, such is the force that seems to reverberate around the old girl when running over an unexpected pothole. is this a 16v quirk due to the stiffer suspension set-up, or is there something (bushes?) that could do with replacing? the bushes, as far as i'm aware, haven't been touched in 100,000 miles and 12 years. i did replace the suspension struts a few years back though.

thanks as ever.

[Vanny]

The valver also has a stiffer anti roll bar and slightly different ARB mounts which certainly dont help the ride, but the biggest difference is deffinately the spheres.

What tyres/pressure are you running as this also has a big impact. 17" alloys will pick up every single knot and bump in the road.

[kiwi]

but the biggest difference is deffinately the spheres.

You made me start thinking about the spheres. I am wondering if my TZS is not fitted with GTI spec sphers? The ride is harder and I notice more in the TZS the bumps on the road than the TRS. I was also thinking of putting it down to the seating quality? The TRS has the traditional bucket design where the TZS has the more firmer GTI type.

How can you tell what the sphers are by visual inspection?

[MULLEY]

Robc, this seems to be a common affliction amongst my fleet, it would appear that they system cant react quick enough, so its always feels quite pronounced, the vibration that is. New front spheres have helped a bit, perhaps the rear spheres affect this also?

As Vanny has mentioned, low profiles on wider than 14 inch wheels will certainly exacerbate this problem.

Another thing to think about is, are your rear arms ok? If not they can affect how much suspension travel is available & so the car can feel a bit more jostled by crappy rough roads. Since Ken sorted my rear arms out, the ride has improved slightly.

Kiwi, some spheres are a slightly different size, however, i dont think you can actually tell what size they actually are (you can measure them) or what pressure they should be, unless its written on the sphere itself. It may be possible to see what they are by removing the sphere & looking at the part that screws into the strut (are there any markings?).

Are the spheres on both your cars the same size? easiest way is to get a tape measure & do the circumference, however, there are spheres which are the same volume capacity (size) but have different pressures. As an example, front spheres for the Hatch & Estate are the same size, however they have slighty different ratings.

I suspect that if they are both the same size in your cars, then one is stiffer than the other because its lost pressure over the years. Westroen recommends the following: Main accumulator: every 2 years. Front spheres: 3 years or 40,000 miles Rear spheres: 4 years or 50,000 miles.

Now whether this is true or not i'm unsure, but some people have reported that the ride of their car improved when they changed the accumulator sphere.

[mnde]

Now whether this is true or not i'm unsure, but some people have reported that the ride of their car improved when they changed the accumulator sphere.

Yes I can vouch for this, but for me it was an improvement in damping.

Before, it was stupidly easy for the rear of my BX to bottom out over speed bumps; it was easy to push the car down at the rear by hand onto the bump stops. On the motorway the car handled like a boat.

After the accumulator sphere was changed, there was a marked, permanent improvement. No more bottoming out on bumps and I couldn't push the rear down onto the stops by hand any more.


Mark.

[akarso]

sometimes i'm amazed the whole car hasn't fallen apart, such is the force that seems to reverberate around

I'd suspect interior elements, too. Even if suspension is top notch, it may seem that the car falls apart on every pothole if for example cockpit isn't fixed properly.

In my current BX tightening all the screws, silicone spray and fabric tape made world of a difference in subjective reception of ride quality.

Hovewer, in my previous one I was not able to trace the source of suspension clattering, I even suspected damaged engine subframe, but it wasn't the case, I don't know what was...

[MULLEY]

Loose subframe bolts? or knackered balljoint which appears to be fine when its not, had both of those on my car & once sorted no more clonking sounds

[Dollywobbler]

Mine crashes over potholes, but then the 2CV does too. Maybe it's a Citroen thing!

[docchevron]

How's the ride height?

Lots of things have a large influence on how the car will ride.
Are the height corrector linkages well lubed, and free of play in the bush?
Aerodynamica wrote a brilliant post about sorting the bushes..

Equally, crap in the H/C itself will have an effect on ride quality.

[MULLEY]

Sorry to sound dim Doc, but how does the height corrector have anything to do with ride quality. I thought it just filled with lhm & then locks into place to ensure the car is at that specific height & thats all? Or does it regulate its height all the time pumping lhm in & out of it continously hence it can have an affect albeit small?

[mat_fenwick]

This is my understanding of it (and I know very little about the hydraulics) but if the height correctors are a bit sticky, the car could ride at the wrong height and potentially have less suspension travel than it should...

[kiwi]

Sounds plausable but the first thing to look at I would agree with is tyre pressures.

When I had new tyres fitted the tyre fitter had the pressures up a bit high. On both BXs I have the same make of tyres and both were overinflated, given the TRS has the softer ride of the two the over pressure was certainly noticed.

Reading another TM thread seems to be what this tyre place has as policy, given that this person has TZ100s which I have as well I found it interesting. Does sound a lot of hogwash the reason claimed to overinflate.

http://www.trademe.co.nz/Community/Mess ... x?id=89347

Come to think of it the TRS had a replacement Front HC fitted maybe there is something to Docs theory?

[docchevron]

The HC's are active, and have damping discs in them, with VERY small ports. It takes very little crap in them to make them a good deal less "supple" than they should be.

When the suspension moves the ARB moves the control rod that acts on the HC, therefore it is always active.
Ok, it wont have as big an effect as changing seized struts or knackered spheres, but it does have an effect on ride quality, certainly as far as damping goes.
If you ever strip an HC and rebuild it minus some damper discs the difference is really very marked.

[maxgreenwood]

The height correctors i think are a very important part of suppleness in the system. Fluid is always on the move through there with movement of the suspension. If there is resistance there, say through one of the small holes being blocked, it will transmit to resistance in movement of the anti roll bar which is not just there for stability but is acting on the HC constantly through most road undulations. The freeer (is that a word?) all that linkage stuff is, and the more true the bushings and hinge points are, the more tightly and swiftly the system as a whole is able transmit quick movements to the spheres and therefore the car will react better to quick changes in road undulations like potholes in my opinion.

[RobC]

wow quite a range of options to check then!

thanks guys i'll let you know how i get on. i'm changing the LHM in a few weeks so that may help (or may not).