Rear Deralleur and 42 tooth sprocket

[Shoogle]

I have an 11-42 cassette with a Shimano SLX Shadow+ long cage derailleur. Recently, when I selected bottom gear (it's 24-34 at the front), there was a horrible grating sound. It's not a gear I use very often but I do use it and it was OK before (I changed the chain?). That's maybe why I've just noticed it. I traced it to the 42 ring being too close to the guide pulley but when I tried to increase the angle of the rear derailleur, the 'B' screw was fully in. I held the derailleur down a bit by hand and the noise stopped. I don't think it's anything to do with indexing or the H-L screws as all the other gears are OK. I put in a longer Allen bolt and this works but it's only just catching the cam/stopper (or whatever it's called). The only thing I've changed recently was the chain, about a month ago. Is there a better solution?

[Brucey]

have you perchance made the new chain a link longer than the old one?

cheers

[Shoogle]

No, Brucey, it's the exact same. It was a link too long but I shortened it to match the old one.

[robgul]

Derailleur hanger extender for about £3 on ebay you're sorted.

Rob

[nirakaro]

I have half a recollection that I once solved a similar problem by putting the bolt in from the other side, so that the – slightly larger – head contacted the stopper. Or I may have imagined it! Maybe worth a try?

[Brucey]

yes that might work, but doesn't explain why it worked before and it doesn't now.

Thinking about it nor does chain length; IIRC both RD-M670 and RD-M675 have the guide pulley concentric with the lower pivot, so clearance to the sprocket oughtn't be affected by chain length.

Maybe

- the pulleys have been changed and are different now?
- there has been wear where the adaptor bracket fits to the gear hanger and this has moved the RD slightly?


all seems very mysterious to me...

cheers

[pwa]

Is it possible to slacken off the B screw and slip in a thin spacer (bit of an ally drinks can or something, then do it up again to see, effectively, if a slightly longer screw would do the trick?

[Shoogle]

I was out on the bike today and tried bottom gear. The longer allen bolt is working and it'll do till I get a better solution. Thanks for your input.

[rualexander]

I have an slx m7000 11 speed rear derailleur working well with a 50 tooth sprocket on my mtb, it worked with a 46t without adjustment but for the 50t I had to screw the normal B screw in a few turns.