So I am a complete novice when it comes to bike maintenance but working on a project mtb, old Saracen rufftrax.

The rear derailleur was knackered so fitting a new SRAM x5, my question is do I need to buy a separate bolt/nut to fit it properly? The derailleur didn’t come with one and the derailleur seems to have too much movement.

The bolt I am on about would be for the hole in the centre of the picture where it attaches to the hanger

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2 Answers 2


I assume you are using the derailleur bolt from the original with the new derailleur. Derailleur bolts are standard M10 x 1.0mm pitch, so that should be fine. The derailleur should rotate around that bolt, as long as it's not loose and does not have any play it's OK.

Without a chain installed the range of rotation will be quite wide, especially if the b-screw is wound out. After installing the chain, just adjust the derailleur properly and you should be OK.


Make sure the B-screw adjustment washer is in place. If it isn't the derailleur would move laterally on the bushing the bolt goes through.

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BTW if you are a novice, there is plenty of bike wrenching instruction on the web. the Park Tool site and YouTube channel is a great resource.

  • Thanks for that, I am not using anything from the old derailleur. I took the old one off and then basically the new SRAM x5 just has a bolt already in it and I just threaded that through the hanger, it feels like another bolt needs to go through that one though, that right? Mar 13, 2019 at 7:30
  • @MatthewStott where you’ve written bolt in the question... do you mean nut?
    – Swifty
    Mar 13, 2019 at 7:52
  • No I mean bolt, if you look at the picture, the bolt in the centre of the pic I have put through the hanger. But can you see there looks like there is a hole in that bolt for something else to go through. I can basically move the derailleur side to side to obviously not right Mar 13, 2019 at 8:39
  • The hole in the bolt is where you insert the allen wrench. Mar 13, 2019 at 12:07
  • There is just a single bolt that screws into the hanger. Are you missing the b-screw washer? See update to answer above. Mar 13, 2019 at 12:07

You are using a derailleur hanger that is too small for the frame. The hanger needs to fit exactly (like a jigsaw puzzle piece) inside the frame dropouts.

It looks like you took off the old derailleur hanger with the old derailleur. If the hanger is still ok, you'll want to use that old derailleur hanger and mount your new derailleur to it.

Derailleur hangers unfortunately come in hundreds of shapes, so getting an exact match can be challenging if you don't work through either the manufacturer or a local bike shop (that in turn often sells that brand of bike).

  • Agreed it’s not quite the right hanger, but it has the right bolt holding it in, along with the QR clamping force, which is likely plenty. I doubt the play is coming from the hanger, @matthewstott should be able to confirm this.
    – Swifty
    Mar 13, 2019 at 14:25

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