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GS550 Upper Rear Shock Mount Stripped

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    GS550 Upper Rear Shock Mount Stripped

    Hi All,

    I have looked through the forum on this question, and can see many suggest taking the old mounts out and welding a new one in ... but!

    I wondered if I could get some views on my predicament.

    The left (upper) rear shock mount is pretty well stripped (not by me!).

    I noticed this when I took the shocks off to fiddle with and repaint.

    It had a M10 (nylock) bolt on it, installed by the previous owner.

    I am thinking to (perhaps!, based on your wise thoughts!) get a die and reduce this to an M8 metric coarse.

    I think I have to go to this size as the core diameter of the (stripped) stud/bolt is about 8.5mm

    I see previous people have had success with a 3/8 x 16 UNC ... but the 'outside' diameter of the threads on this would be 9.5mm ... so wont work in this case?

    Whereas an M8 bolt has a core = 6.5mm and outside = 8mm ... so I'd emery off about 0.5mm!

    I suppose my main question is will a M8 bolt be okay ... or is this too small?

    I note that the 'general recommendations' are that a M8 bolt has a torque of around 30Nm, whilst a M10 has a torque of 55Nm ... this is my worry!

    I think the Upper shock bolt's torque is around 34 - 52 Nm ... in the service manual?

    Any thoughts and wise advice welcome.

    Cheers Niall (& Fergus)

    1980 GS550E (Sussex, UK)
    GS550 1980

    Any welder can remove the stud and put a new one on. Overall that would be the cheapest strongest option.
    Well not any welder. An actual trained certified welder that works for cash not beer money.

    Call a local fabricator and ask.
    1983 GS 550 LD
    2009 BMW K1300s


      ^^^that'd be the best but the torque on these at about 40ft/lbs is not huge- they aren't supposed to be super tight-that's likely how they were stripped. There isn't a lot of sideways thrust trying to get the shocks off especially if youre mostly trundling on streets...Force is mainly upndown and the thick unthreaded portion is built for this. The threaded portion less important..

      That said, the shocks do try to turn the bolt a little wee bit-they don't exactly match the arc the swing makes when it moves a lot so you might like to add a bit of threadlock...and have a slippery shiny washer against the capnut...

      While you're at it, do check that your shocks line up FROM the swing arm TO the mounts when they are relaxed...shocks work best and last longer when they are not slightly they are not being forced sideways to match a particular configuration of washers. They may already BE bent so rotating one end 180 degrees will show this and can help match up if this is the case.... Use the washers to fill the gaps exactly or even loosely rather than torquing the shock ends in or out. It may even discover a swing arm issue- an adjustment there can help the chain and sprockets (or shaft)and the shocks and the feel of the bike overall too ..
      Last edited by Gorminrider; 06-09-2022, 10:29 AM.


        Bit of a digression there! sorry. but what choices do you have excepting a new stud welded? JBweld? with a BIG nut? I'd want it wired on too as a backup much though I love the stuff.

        Cotterpin? there's a thought... and yet another "thought"- if you do cut new threads, you'll remember that dies start with a shallow cut before finishing with the final deep cut. You will not want to transgress on the unthreaded part of the stud very maybe you can turn the die around to cut a little more deeply furthe,r before gaily cranking a new nut on and stripping everything again...sometimes a sacrificial nut -r stainless being hard -can help cut deeper threads and/or use a brass nut as the final...carefully in either case.