Fitting a seat shock absorber

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Charles Morgan

MB Enthusiast
Feb 2, 2010
Mercedes 250CE W114, Alfa Romeo GT Coupe 3.2 V6
My BMW M535i has 4 seat shocks fitted - two for height and two for backrest angle. All are a bit past it, the result being that if you try to adjust backrest angle the seat will simply collapse to horizontal. Not helpful on the move.

I bought some replacements, and managed to fit the first height adjustment one today. This was an utter pig, as the shock is un-compressed prior to fitting and it is 350nm to compress it. Each of the holes slots into a stud on the seat base. I was able to do it using my bench vice, but that meant moving the seat around on the work bench. Took 3 hours of fiddling and cursing, and that is the easy one.

The rear back rest one is horribly more tight to fit. Any ideas on a portable tool of limited size that might be usable to compress this one for easier fitting? It's about 15 cm long and would need to compress about 5 cm to fit the studs.


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Compress in your vice and use tie wraps to hold during positioning?
The latter will block the holes (they are 5mm with tiny clearance) and I tried a variant with electrical flex. It's quite fun to watch how much stretch a 350nm gas strut can generate!

A form of spring compressor is possible, but more than 5mm overhang on the hook and it will get in the way of the studs fitting into the strut's holes.
Googling it I found this "installation instruction" which although it probably isn't for your car, does demonstrate using a trigger clamp. Don't know if it would be feasible in your situation?

Installation - BMW Seat Shocks
That's exactly the same set up as mine - absolutely perfect, thank you! I didn't find such a comprehensive guide when googling, so double thanks.
Found this clamp (the DeWalt one is not available in the UK that I can see) with 270kg of clamping force. I think that should do it.
Could you compress the shock the put a ratchet strap around it ?
My clamp arrived today - perfect!


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As it was raining I decided to attempt to fit these shocks with the tool. The side ones controlling seat height were under a minute each. Joyfully, blissfully easy. This then lulled me into a massive sense of complacency. The seat angle controlling ones are beyond belief. After an hour with the clamp all chewed up (the jaw liners have no strength to cope with the immense pressure exerted by the end of the shock) I've got one fitted and now I'm taking a break. Of course, can I get retail quantities of the push nuts, nope, 200 on their way...


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Blimey Charles, looks a pig of a job. I'll bet it's one you'd not want to have to do again.
Did the last remaining one and thank heavens for that. The seat now works perfectly, but who in their right mind devised something entirely dependent on shock absorbers when a wheeled ratchet would do the job perfectly. Odious piece of design. Having worked on my 1984 BMW M535i a lot I would say that the build quality is a long way off Benzes of the same period. The engines and handling though, more than make up!

Oh and the passenger can swivel, backwards, rapidly. I'm not doing their seat!

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