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912 suspension travel/shocks shot?
Posted: Sun Jan 01, 2017 9:28 pm
by gturner008
I really want to sort out a small problem with the '67 912 before it goes to auction on the 14 January.
I've noticed a clunk on the LHS front when driving along and hitting a bump in the road.
I've tried replacing the anti-roll bar /sway link bushes, but clunk still there.
With the car jacked up, and pushing the front wheel up and down I notice a movement of about an inch (30mm) in the suspension - with the free play coming from inside the shock absorber.
Am I right in thinking it's a simple case of my shocks shot? Are they adjustable or do I need to simply replace the strut inserts or get a repair kit? I think the strut is Bilstein, but need to check.
Cheers for any advice and help... Gary
Re: 912 suspension travel/shocks shot?
Posted: Tue Jan 03, 2017 5:37 pm
by gturner008
I've tried winding up the torsion bar five adjustment, to see if that sorted out the knocking sound when going over rough ground. No joy. Knocking still there.
I've checked every joint/bush etc, and absolutely no movement at any place. I'm thinking it has to be a duff shock absorber? Any other suggestions?
Re: 912 suspension travel/shocks shot?
Posted: Tue Jan 03, 2017 6:18 pm
by KS
Let me know when you find it then I can stop mine knocking...
Re: 912 suspension travel/shocks shot?
Posted: Tue Jan 03, 2017 8:41 pm
by gturner008
Will do. I'm strongly favouring the shock absorber.
Re: 912 suspension travel/shocks shot?
Posted: Thu May 11, 2017 11:57 am
by 55ovalcharlie
in case you haven't solved your issue - this post by Chris from FennLane Motorsport solved my issues - particularly the bit about inserts being a bit too short and needing shims to eliminate the clunking.
fetuhoe wrote:This is almost certainly a BOGE strut case as the Koni case used on SWB cars isn't parallel - it has a step change part way down the body,
The BOGE strut body tends to be a 'wet' design with the tube forming the cylinder of the damper.
There is a Bilstein Cartridge insert that fits this strut body (Part No. P36-0111-M512)
These inserts are supplied with a green dust cover.
There used to be two different Bilstein Parts for early SWB strut casings but this changed about 10 years ago when one part was dropped from production.
The problem with fitting these inserts is quite common and due to the poor tolerance of the original BOGE casing.
It is quite common for the new insert not to reach the bottom of the leg and when you tighten up the gland nut there will be some axial float of the insert in the casing - hence the 'clonk' which is only audible at low speed but it there all of the time.
The only way to avoid this problem is to fit shims into the base of the strut casing and ensure that all of the axial clearance has been removed. We have found that shim with a combined thickness of up to 3mm can be needed.
This is not as straightforward as it sounds as the bottom of the strut casing is not flat - it has a small curvature and if a thick plate is fitted it can deform and the problem recurs, this is partly due to the end of the insert being flat and hence mismatched.
It is better to use thin shims say 1mm each, fit them individually and tighten up the gland nut between adding the shims.
Some people fill the casing with oil between the insert and the body and this will help with cooling and will damp out the 'clonk' but it won't stop the movement which will always cause long term damage.
The 'roll pin' used on a Bilstein strut is a bit of a red herring and only relevant to the post 1969 design of strut casing.
full thread is here
viewtopic.php?f=9&t=57076&p=498813&hilit=shim#p498813
Re: 912 suspension travel/shocks shot?
Posted: Tue May 16, 2017 2:42 pm
by neilbardsley
55ovalcharlie wrote:in case you haven't solved your issue - this post by Chris from FennLane Motorsport solved my issues - particularly the bit about inserts being a bit too short and needing shims to eliminate the clunking.
fetuhoe wrote:This is almost certainly a BOGE strut case as the Koni case used on SWB cars isn't parallel - it has a step change part way down the body,
The BOGE strut body tends to be a 'wet' design with the tube forming the cylinder of the damper.
There is a Bilstein Cartridge insert that fits this strut body (Part No. P36-0111-M512)
These inserts are supplied with a green dust cover.
There used to be two different Bilstein Parts for early SWB strut casings but this changed about 10 years ago when one part was dropped from production.
The problem with fitting these inserts is quite common and due to the poor tolerance of the original BOGE casing.
It is quite common for the new insert not to reach the bottom of the leg and when you tighten up the gland nut there will be some axial float of the insert in the casing - hence the 'clonk' which is only audible at low speed but it there all of the time.
The only way to avoid this problem is to fit shims into the base of the strut casing and ensure that all of the axial clearance has been removed. We have found that shim with a combined thickness of up to 3mm can be needed.
This is not as straightforward as it sounds as the bottom of the strut casing is not flat - it has a small curvature and if a thick plate is fitted it can deform and the problem recurs, this is partly due to the end of the insert being flat and hence mismatched.
It is better to use thin shims say 1mm each, fit them individually and tighten up the gland nut between adding the shims.
Some people fill the casing with oil between the insert and the body and this will help with cooling and will damp out the 'clonk' but it won't stop the movement which will always cause long term damage.
The 'roll pin' used on a Bilstein strut is a bit of a red herring and only relevant to the post 1969 design of strut casing.
full thread is here
viewtopic.php?f=9&t=57076&p=498813&hilit=shim#p498813
He sold it ages ago and is buying new cars in Canada.
Maybe whoever bought it might come on here and look for help?
