SRAM x5 derailleur fitting 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
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.



Update:

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.

 



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.