Suspension too stiff?

[hunker7]

Hi guys. My S4 is running B6 Bilsteins all round with Audis 1BE sport springs. Is it possible that this combination is too stiff? Both of my Lemforder top mounts have been shredded within 8 month and literally every little bump in the road is felt even on 225/55/16 tyres. I'll be going back to OEM style front subframe bushes from solid aluminium but don't see that making such a huge improvement.

[steve briance]

Lago Blue has posted several times about b6 dampers suffering from hydraulic lock... I don't know if the struts are the same on your car to the b3/b4 mcpherson design but they fill up with water and the upside down damper design of the b6 cannot operate properly in water. The solution is to drill a small hole at the lowest point of the strut tube to let the water out. If the water can't escape, the da per piston is trying to go up and down in a virtual sealed tube half full of water which cannot be compressed...

[hunker7]

It's same design but I can't see how water gets on there as B6 caps have a rubber seal on it?

[steve briance]

Well, this is the confusion but it sure as hell does happen. Bilstein actually used to advocate in their installation; drilling the hole and they wouldnt do that unless it was necessary. I drilled the hole when I installed mine and when priming the shock by cycling it through full travel a couple of times, I noticed there was a considerable vacuum at the hole on the upward stroke (piston moving away from the hole) It is not impossible to imagine this vacuum at the seal sucking in a little water or more likely moisture in the atmosphere which then condenses inside the tube. Over time that builds up.

Search for the thread - there are links to other forums (Quattro world I think) and many photos that show what happens and the fix.

It's a PITA taking it all apart to check but the forums quoted in the thread had a Common theme in that ride comfort got worse and worse and started shaking the cars to bits...

[S2central.net]

I was reading about this exact phenomenon on the forum recently - there are some lengthy discussions about it.

[steve briance]

Found it! Long read but probably worth it when considering the time it takes to strip a damper out of a strut to have a look...

https://www.s2forum.com/forum/technical/suspension-steering/79476-bilstein-into-macpherson-strut-install

[hunker7]

I'll take them out tomorrow and check as it's super easy on C4, no need to take struts out at all. Worth a check. Thanks for the info mate. I'll report back tomorrow.

[Lago Blue]

Holger-Neilson-Bilstein Maneuver

Hunker,

IIRC, this issue may have first surfaced years ago on US forums for UrS platforms such as yours. Steve has outlined it above pretty well. Beyond the lack of comfort, and that the steering & handling gets dicey without suspension travel, the mechanical risk of hydro-locking; even if only partially, is that the dampers are vulnerable to being blown apart internally, which will of course require their replacement.

I blew mine the first time because I was transiting across the continent at the time and didn't understand what the odd symptoms were trying to warn me of. The second time I got lucky, just barely I think. Your dampers will be large OD base-vented units, mine (as you may read of below) where small-bore un-vented base units, but the same technique (save for perhaps having to work them upside-down) will work for you, just easier/faster to dry yours out internally with the vents on them.

If caught soon enough, you might resuscitate your B6/8s by as follows:

https://forums.quattroworld.com/9080/msgs/12447.phtml

Hth.

[hunker7]

Ok couldn't get them out unfortunately as even with grease the bloody caps have seized on What I am noticing is that passenger side shocker is easier to push down compared to drivers side which require hell of a lot to get compressed. I've attached pictures of my 8 month old Lemforder mounts as well.

You mentioned steering issues, any particular behaviour?

[hunker7]

This is how much travel suspension has when I push down on front end as much as I can, barely moves

https://www.dropbox.com/sh/wo76s694h0t87gg/AACeJ5U9peHC1HWS0P27rrK7a?dl=0

[Lago Blue]

You're not beat yet. See rusted cap removal procedure in link Steve posted above.

[hunker7]

You're not beat yet. See rusted cap removal procedure in link Steve posted above.

It's still on the car mate, was hoping to remove damper without removing the whole upright.

[Lago Blue]

Eventually the steering wheel will vibrate so bad you won't want to be holding it, but before that your front end will want to under-steer worse than normal (the available front suspension travel is shrinking towards zero) and more suddenly, i.e. when that outside strut reaches the new foreshortened compression limit and snaps to full solid in the middle of a corner, that tire will want to start to slide. But your back end is still "normal" i.e. soft or relatively "softer" than up front, you'll likely take your foot off the gas, the resulting weight shift goes forward to that hydro-locked strut and you are riding a curling stone. Please don't try this.

Your top-mounts aren't made to provide meaningful suspension travel, so when your strut(s?) hydro-lock(s) and no longer can absorb any energy, they merely transmit it near perfectly into the perhaps stock top-mounts; which of course then over-extend vertically, tear and totally fail. Now your strut tops are free to wobble and you'll see that eventually at the steering wheel.

Hard to tell how "full" your struts may be from your video, doesn't matter anyhow, they don't have to fill to fail. The broken top-mounts are perhaps now allowing more vertical travel than otherwise, meanwhile your A/R bar is likely torqued all the time trying to prevent the most "full" strut from having to carry the entire weight of the front-end of the car (approx. 2/3rds of your GVW) alone. I believe I've seen worse (i.e. zero movement on either side) but then again; my top-mounts didn't fail! Perhaps you can guess why. When you get in there, evidence or absence of damper oil will be key to what's then perhaps required for your dampers.

[hunker7]

Can I drill the whole at the bottom of the upright while shock absorber is still in place? Last thing I wanted to do is take uprights of again as it's an absolute ball ache of a job.

[hunker7]

Aside from harsh ride it drives beautifully. Steering is spot on and there no vibration even at bloody 100mph.