Suspension questions

[ianc]

FL I agree that the buffers don't seem to make sense. They are original fitment but I couldn't get more than that from Mercedes Ireland.
They will most likely be repurposed as air bag supports if I go down that route. I'll move them as close to the axle line as I can first though.

Mark - That travel is amazing, but now its clear to me that it's more than I can achieve with air bags and without some major surgery. Its also probably more than I need for bad roads (I'm thinking that type of journey Julian/Gait just completed).

I suppose the question for me now: Is 200mm, which is the practical max of air bags, enough to give a good ride on crap roads?

In considering going down this route, it concerns me that almost nobody else has used Air Bags......

BTW - I bought a small usb camera with a long cable to video the suspension movement while driving. I'm going to do a few runs today if the rain holds off. Watch this space.

 

[ianc]

Here's some video of the suspension working and the road travelled. I was doing no more than 55kph.

First here's the road section. Uneven surface and extensively and poorly patched by Wicklow County Council.
[video]https://onedrive.live.com/redir?resid=CDD8627ECC9D7918!12072&authkey=!AN0cmp HgOFKZ2s8&ithint=video%2cmp4[/video]

And now the front suspension. Not as much travel as I'd though, but clearly it's bottoming out. The severe bottoming out at the end was the braking. I didn't slam the brakes on.
[video]https://onedrive.live.com/redir?resid=CDD8627ECC9D7918!12076&authkey=!AMsU1W QT_88wbgo&ithint=video%2cmp4[/video]

Here's the rear suspension. Video quality is poor but you can see the movement. It never bottoms out but there is much more movement than I'd expected given my suspision that the rear springs were too stiff. Doesn't look that way.
[video]https://onedrive.live.com/redir?resid=CDD8627ECC9D7918!12075&authkey=!AAmGVU M-s3mGEXc&ithint=video%2cmp4[/video]

Finally some photos of the suspension.

Rear spring set-up. Three parabolic leaves with the bottom one heavier and only activating under load.


And the anti-sway bar on the rear - 50mm diameter and solid . I'm a little scared to disconnect it given the 3.5m height of the vehicle.



And for completeness, here's the front anti-sway bar - 38mm and solid

 

[ianc]

Here's the Air bag option I'm considering:
http://www.fsip2.com/pdfs/industrial/datasheets/METRIC_PDF/1T14C-7.pdf

 

[gait]

more questions than answers .... I should have realised the leaves are subject to high frequency oscillations between ends and axle (the blurry bits of video) - looks like that odd bump stop may be there to damp them.

Is the other side the same? Does it move the same? How old are the springs (km)? What's the clearance to front bump stop (uncut) as new? Cracks hidden under axle? U-bolt torque?

Not enough info but springs progressively sag over their life. End of life of spring is when it doesn't do its job, when it breaks is way past that. Permanently laden (like a camper) rather than changing load (like delivery van) can apparently shorten life. Resetting / retempering springs can extend the life but not as good as new.

Cutting off the central bump stop may be just covering up sag. I'm guessing the vehicle is old enough to have needed some steering links replaced.

 

[gait]

...
Mark - That travel is amazing, but now its clear to me that it's more than I can achieve with air bags and without some major surgery. Its also probably more than I need for bad roads (I'm thinking that type of journey Julian/Gait just completed).
...

I'm not hard core 4wd by any stretch of the imagination .. this is a little section of steep tight bad road in Morocco that has a few vehicles turn back. One of the few times we had the camera ready for the awkward bits. Clearance and traction seemed more important than 4wd for most of the trip.

 

[ianc]

more questions than answers .... I should have realised the leaves are subject to high frequency oscillations between ends and axle (the blurry bits of video) - looks like that odd bump stop may be there to damp them.

Is the other side the same? Does it move the same? How old are the springs (km)? What's the clearance to front bump stop (uncut) as new? Cracks hidden under axle? U-bolt torque?

Not enough info but springs progressively sag over their life. End of life of spring is when it doesn't do its job, when it breaks is way past that. Permanently laden (like a camper) rather than changing load (like delivery van) can apparently shorten life. Resetting / retempering springs can extend the life but not as good as new.

Cutting off the central bump stop may be just covering up sag. I'm guessing the vehicle is old enough to have needed some steering links replaced.

Yep the other side is behaving the same. A little more bottoming out but I'm confident that's due to being on the kerb side which is more broken up and uneven.

The springs have 230kkms on them and with a constant 70% of capacity load. Mostly on OK roads. So they are almost certainly tired.

Springs on a brand new Wolcke camper (http://www.woelcke.de/category/allrad/car-16/car.php) show a similarly small clearance of 40-50mm. So putting new MB ones on may help a bit, but they won't address the lack of travel.

U-bolt torques are correct and there is no "friction rust" at the axle/spring joint - So unlikely to be cracks or movement. Only friction rust is the point you noted previously where the two leaves are touching.

The only steering/suspension articulation components I've not replaced or thoroughly checked are the kingpins and the rubbers on the spring ends.

Thanks for the question - they help prompt my own thought processes.

 

[ianc]

I'm not hard core 4wd by any stretch of the imagination .. this is a little section of steep tight bad road in Morocco that has a few vehicles turn back. One of the few times we had the camera ready for the awkward bits. Clearance and traction seemed more important than 4wd for most of the trip.

View attachment 243506View attachment 243507

I'd be very happy to get that level or articulation. I'm fortunate in that the Vario has rear and central diff locks for those wheel in the air moments (yet to be tested though!.