Front Mech Chain Rub

[Alba Zeus]

Chain rubs on the big sprocket on the front and small on the back.

I have fiddled with the H screw however it would seem the screw could almost be screwed right out and still there is slight rub.

Chain shifts up and down without issue and there is no rub on the lower sprocket after I adjusted the L screw.

Possible that the cable is too tight thus stopping the cage moving out a millimetre more?

 

[T4tomo]

can you move the cage further out with your fingers? If so you haven't got enough cable tension in "resting mode", I.e full lever travel isn't giving you enough derailleur travel because the first part of the lever travel is taking up cable slack.

or your cage /mech isn't aligned properly (height and / or plane) so a part of the cage is catching the chain

 

[Alba Zeus]

Hi, yes I can move the cage out manually so that there is no rub.

Cool so more tension in the cable

Many thanks

 

[Alex321]

Chain rubs on the big sprocket on the front and small on the back.

I have fiddled with the H screw however it would seem the screw could almost be screwed right out and still there is slight rub.

Chain shifts up and down without issue and there is no rub on the lower sprocket after I adjusted the L screw.

Possible that the cable is too tight thus stopping the cage moving out a millimetre more?

Depending on the model, that H screw may not actually be doing what you expect.

Unlike the rear derailleur, where those screws usually just set the limit, on some front derailleurs what the H screw actually sets is the point at which the lever movement engages, and the cage starts moving. So turning the screw in more means it engages earlier, and the cage ends up further out at the limit of the travel.

I don't know how common this is, but it is what mine (Shimano FD7000) does.

 

[Alba Zeus]

Managed to sort it.

Rejigged the cage, tightened the cable and there is a little 2mm screw for precision on the inside of the mech so diddled with that and it is all running lovely now.

Thanks for the comments, appreciate your time

 

[Alba Zeus]

When fitting the front derailleur should the limit screws be all the way in or all the out to start with or does it matter?

 

[T4tomo]

I normally start with out, so the mech movement is unrestricted and then work from there.
Set lower limit before attaching cable. Then attach cable and then check whether you need to restrict upper limit.

 

[Alba Zeus]

I thought as much. First time adjusting one of these new front mechs with the frame support bolt but seem to have managed it