Derailleur cage fouling large sprocket

[ASC1951]

Any ideas of the cause of this problem? On my Campag triple I can't get the biggest sprocket in middle ring or granny because the top of the rear derailleur cage rubs on the sprocket teeth.

It's definitely nothing to do with wrong size of cage or incompatible cassette - I have had this setup for five years and it's only developed in the last few hundred miles. Ditto chain length, I'm fairly sure.

I have had the cables renewed so cable stretch is a possibility, but that hasn't affected it before. I assume that the tension spring within the derailleur does weaken with age, so could this be the cause? I also wonder if I have mistakenly put the derailleur back on at the wrong angle i.e. without tensioning it against the spring, but that doesn't seem very likely because there is a pivot stop on the housing to stop you doing that.

My guess is that the spring within the derailleur needs tightening or replacing, but before I try my circlip pliers and short sight on it - or more likely open my wallet at the LBS - have I missed something obvious?

 

[PatrickPending]

agree with the above, see

http://www.parktool.com/repair/readhowto.asp?id=64

 

[jayce]

agree with the above, see

http://www.parktool.com/repair/readhowto.asp?id=64

yes if you adjust the b screw clockwise it puts tension on the rear mech causing it to be pulled away from the cogs so it dont touch and wreck your mech

 

[ASC1951]

I did look at the Campag Service Manual but didn't find it very helpful.

My rear derailleur doesn't have a B screw which acts against the frame as in the Park Tools photo, so my B screw must be the one at the top of the cage. I did look at that but there didn't seem any travel left on it - I hadn't appreciated that it was a rack and pinion adjustment.

[Jayce, according to Park Tools, I have to turn that screw counter-clockwise to pull the cage away from the sprocket.]

I shall get my little short sighted eyes on the job. Thanks all.

 

[jayce]

I did look at the Campag Service Manual but didn't find it very helpful.

My rear derailleur doesn't have a B screw which acts against the frame as in the Park Tools photo, so my B screw must be the one at the top of the cage. I did look at that but there didn't seem any travel left on it - I hadn't appreciated that it was a rack and pinion adjustment.

[Jayce, according to Park Tools, I have to turn that screw counter-clockwise to pull the cage away from the sprocket.]

I shall get my little short sighted eyes on the job. Thanks all.

i run ultegra if i turn it anti clockwise it will slaken the tension and will foul the cogs

 

[jayce]

i run ultegra if i turn it anti clockwise it will slaken the tension and will foul the cogs

i see now fella we run different mechs my bad