Can I make the derailleur gap to the largest sprocket slightly larger?

[buzzy-beans]

I have just fitted a replacement cassette with a wider set of ratios, it all fits and works perfectly with the single exception that there is next to no gap between the largest sprocket and the first slightly toothed wheel on the derailleur, in fact I think they are actually touching!

I feel sure I saw a small extension piece advertised somewhere on the internet that fitted between the bike frame and the derailleur, but can I find it now, can I hell as like.

Does anyone have any ideas please?

 

[Tim Hall]

Adjust the "B" screw. It's the small one in the trailing edge of the mech.

 

[Tangoup51]

and make sure you're using a bike stand, and not flipping the bike upside down.

 

[youngoldbloke]

I have just fitted a replacement cassette with a wider set of ratios, it all fits and works perfectly with the single exception that there is next to no gap between the largest sprocket and the first slightly toothed wheel on the derailleur, in fact I think they are actually touching!

I feel sure I saw a small extension piece advertised somewhere on the internet that fitted between the bike frame and the derailleur, but can I find it now, can I hell as like.

Does anyone have any ideas please?

ROAD LINK - rather expensive for what it is, but a less pricey copy is available from China

 

[pclay]

As above, assuming your derailleur can accommodate the cassette, then you need to adjust the B screw.

If not, you can use a wolf tooth road link. What cassette have you fitted and what derailuer do you have?

 

[Illaveago]

Do you mean that you need to drop the rear mech slightly ?

 

[Racing roadkill]

Turn the B screw on the rear mech clockwise, until the ‘angle of dangle’ increases enough to give you more clearance to the jockey wheel.

 

[buzzy-beans]

Do you mean that you need to drop the rear mech slightly ?

Yes, and thanks @Tim Hall & @Racing roadkill, I will now go and see if I can find the illusive 'B' screw.

As if and when I have adjusted the 'B' screw and it works will the resultant acute bend in the chain create an increased amount of drag/friction and general chain wear?

 

[Illaveago]

So the B screw is an adjustable stop screw which should either allow the rear mech to assume a more vertical position, or does it apply more tension to the jockey wheels and allow it to clear the large sprocket .

 

[Racing roadkill]

So the B screw is an adjustable stop screw which should either allow the rear mech to assume a more vertical position, or does it apply more tension to the jockey wheels and allow it to clear the large sprocket .

It just opens up the angle of the cage in relation to the cassette, this will have a ( negligible) effect on the strain experienced by the chain, but it’s better than having the chain fouling the cassette at the top jockey wheel.

 

[Racing roadkill]

Confusingly, it’s the screw marked ‘A’ in this picture. B ( in this picture ) is the limit adjuster for the smallest sprockets ( H screw ) C is the limit adjuster for the biggest sprockets ( L screw). If you turn the screws clockwise, the mech limit moves outwards ( towards the small sprocket end of the cassette ) if you turn them anti clockwise, it moves the mech limit inwards (towards the largest sprockets / spokes) turning the screw marked ‘A’ in this picture clockwise, moves the cage down, anti clockwise will result in the cage moving up. Think ‘clock out’ and you’ll be right. E ( in this picture) is the indexing screw, again, think ‘clock out’ and you’ll be right.

 

[Will Spin]

If you fitted a larger cassette, you may also need a longer chain.

 

[buzzy-beans]

All done and dusted, it only needed the smallest amount of adjustment.
As for the longer chain @Will Spin, a new one was all part and parcel of my recent upgrade.

Many thanks

 

[smutchin]

As if and when I have adjusted the 'B' screw and it works will the resultant acute bend in the chain create an increased amount of drag/friction and general chain wear?

Don't know about this but I do know that the instructions for fitting Shimano mechs advise to keep the gap as small as possible (though obviously not actually touching). I believe this is supposed to improve shifting performance.

 

[youngoldbloke]

All done and dusted, it only needed the smallest amount of adjustment.
As for the longer chain @Will Spin, a new one was all part and parcel of my recent upgrade.

Many thanks

That's good! What mech and cassette are you using BTW? I'm thinking of trying a 11-32 or 34 t cassette with my 9 speed Tiagra (short cage) It works fine with a 30t at the moment.