I was working on my bike and was about to add some more tension to my SLX clutch mech. While trying to remove the clutch cover I accidentally rounded off the bolts, so I have no way of getting the clutch cover off.

What should I do, can I get the bolts out, can I buy replacement bolts?

Thanks in advance.

  • 1
    Do you mean you rounded off the hex shaped hole on heads of the bolts that retain the clutch cover? If so, what did you do to achieve that? Those bolts surely are not torqued in tight. Are they corroded in? Commented May 2, 2018 at 16:44
  • 1
    There are screw extractors although it might be fiddly with small screws. Those screws were probably locked with threadlocker and not meant to be removed (think no user serviceable parts!). So you can try an extractor but then also the tool could be more expensive than just getting a replacement derailleur and there's still the risk of damaging the derailleur.
    – Carel
    Commented May 2, 2018 at 17:39
  • 1
    Why were you adding tension - if you were not dropping the chain, most probably anything you do from now it make it worse. Might be best to leave it with view to replacement now some time in the future..
    – mattnz
    Commented May 2, 2018 at 20:24
  • 1
    You could try drilling out the bolt (might be easier than finding an appropriate screw extractor; its probably a small 2mm hex bolt), but chances are you're going to end up getting a new derailleur cause this is going to be fiddly. Alternatively, if you're careful, i suppose you might be able to dremel around the clutch cover to cut it off without damaging the rest of the derailleur, assuming the cover is just to keep dirt out. Not ideal.
    – Batman
    Commented May 3, 2018 at 1:35
  • 2
    Can you, please, post a picture of the bolt in question, so we all know what exactly is the problem and we can give you a tailored advice?
    – Mike
    Commented May 3, 2018 at 9:38

2 Answers 2


If by "rounded" you mean stripped, then you can follow the next steps:

  1. Get a hold on a dremel with a cutting wheel, and Draw a line from side to side(Over the center, like a Diametre line) about the same depth of the hex tool that was supposed to loose the bolt.
  2. If possible, rotate 90 degrees and do the same a point 1
  3. Dip the the part in "Light Coke"(this thing works wonders on siezed bolts, not so much on your health tho) for about two hours. If you can do it overnight, that's ok too.
  4. Optional to (3.), pour some wd-40 on the bolts and threads. If it's has threadlocker then you will need a solvent, like Isopropil alcohol, acetone, or just a plain soldering iron to heat the bolt and soften the thing.
  5. Use a Slot ScrewDriver on the lines you made with your dremmel.

This is by far the safest way to remove stripped bolts.

Other method i've used include to drill a hole on the bolt, and then screw a special tool with counterclock thread to unscrew the bolt out of place, while you screw in the tool. Also you could just drill the bolt out, but you might get to damage the threads on your dereaullier.

The last method, only works on a couple of situations where the thread are not seized, is to take the head of the bolt out. This will take tre preasure off the thread and you can fiddle with it until unscrewd. Did this on a KTM Duke 390.



Use a torqx head (8 or 9 should work) and try to use as little force as you can to remove the three bolts.old m785 shadow+ mech with rounded out bolts-they can be removed but not with the intended 2mm allen key (My old m785 with rounded out bolts...I learned my lesson)

Try to really push the torqx head inside while turning otherwise you might damage the bolt even more. If the bolts are “usable” using a torqx head than just don’t replace them. Also the clutch mechanism is made to be serviced, unlike sram, by adding shimano hub grease between the tension spring and the roller clutch or even replace certain parts if needed. DO NOT ride without the clutch cover because that will only allow the dirt, dust and water to enter the mechanism and potentially ruin the derallieur.

Hope this helps

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