Niggly niggly derailleur not quite right annoyance

[Fnaar]

The bike is perfectly ridable, but it just isn't right
When in lowest gear (small front, big back) the run of the chain through the jockey wheels makes them 'rumble' and you can see them shaking a bit when it's on the stand, and the bottom one is a fraction nearer the wheel than the top one. They jockeys themselves aren't loose, they are in good nick, the chain is clean. You can see that the chain line is not good. The hanger is not bent (LBS checked it for me), the front rings are not bent either, it's indexed OK (I can do that, just done it now).
It's similar in big front/smaller back combos, chain line not good, ride not as smooth as it should be. The only other thing I can think of is if the wheel is not quite right in the dropouts, but I can't see how I've done that any differently from any other time. And I'm not sure why bottom jockey wheel is a tiny bit nearer the wheel. If I toy with chopping my fingers off and pulling the bottom of the derailleur out a tiny bit while the wheel is going round, it makes the 'rumble' a tiny bit better, but not much.
Anything obvious you can think of, folks?

 

[cyberknight]

B screw adjustment?
http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

 

[Fnaar]

B screw adjustment?
http://www.parktool.com/blog/repair-help/rear-derailler-adjustments-derailleur

No, that's OK too

 

[screenman]

I would have the hanger rechecked if you are sure everything else is perfect.

 

[I like Skol]

How has the LBS checked the hanger straightness? If they just eyeballed it then it could still be out. The aim is to get it in line with the rear wheel. I do this with a 1mtr steel straight edge/ruler. First remove the rear mech then place the straight edge midpoint on the hanger eye with the ruler pointing towards the bottom bracket (it might have to be just above or below the chainset if it clashes with the cranks). You then need to measure the distance from ruler to rim braking surface at either side of the wheel and if the hanger is straight in this direction they should be near as dammit the same. You then repeat this check in the vertical plane, so 90 degrees from the previous check. Once you establish if there is any 'wrongness' about the hanger you can tweak it (I use a small-medium sized adjustable spanner) by bending it a little until it all lines up or replace the hanger. If you decide to replace the hanger you will still need to check the new one is sitting straight. Also, make sure you carry out these checks with the wheel in place and Q/R tightened up as you will be surprised how much the hanger can move when the Q/R is tensioned.

 

[Fnaar]

How has the LBS checked the hanger straightness? If they just eyeballed it then it could still be out. The aim is to get it in line with the rear wheel. I do this with a 1mtr steel straight edge/ruler. First remove the rear mech then place the straight edge midpoint on the hanger eye with the ruler pointing towards the bottom bracket (it might have to be just above or below the chainset if it clashes with the cranks). You then need to measure the distance from ruler to rim braking surface at either side of the wheel and if the hanger is straight in this direction they should be near as dammit the same. You then repeat this check in the vertical plane, so 90 degrees from the previous check. Once you establish if there is any 'wrongness' about the hanger you can tweak it (I use a small-medium sized adjustable spanner) by bending it a little until it all lines up or replace the hanger. If you decide to replace the hanger you will still need to check the new one is sitting straight. Also, make sure you carry out these checks with the wheel in place and Q/R tightened up as you will be surprised how much the hanger can move when the Q/R is tensioned.

The LBS checked the hanger with his guage thingy... not quite sure what to do next, as it's perfectly rideable, but I know it's 'out' just that annoying little bit.

 

[John the Canuck]

'bouncing' happened to me when the top jockey wheel contacted the tops of the smallest cog teeth

 

[Fnaar]

'bouncing' happened to me when the top jockey wheel contacted the tops of the smallest cog teeth

Yes, I've had that before, but remedied with 'b' screw.
Poss because it's a mish-mash of diff components (Shimano derailleur, non shimano cassette.... just a bit mismatched.... dunno really.
TBH, it's annoying rather than ride-limiting, so have now put it away till I ride it on Sunday

 

[dan_bo]

Is the mech extending properly? If its not rotating backwards cos the spring is clogged with biz then the chain wont sit properly. Diesel is your friend.

 

[Fnaar]

Good call @dan_bo I tend to keep things quite clean, but I'll have a gander when I get a chance. Trouble is, I don't get enough fettling time

 

[dan_bo]

Good call @dan_bo I tend to keep things quite clean, but I'll have a gander when I get a chance. Trouble is, I don't get enough fettling time

im forever fiddling. Usually on my own.

 

[wisdom]

Some pics may help if you can post some

 

[Fnaar]

Some pics msy help if you can post some

Bike's away now till Sunday, and not easy to get it out of its resting place right now... but will do if I get a mo. Not sure they'd show much though, but I do know there are more expert eyes on here than mine.

 

[Crackle]

Is it a removable hangar, if so check the bolts that mount it are tight, check the jockey wheel bolts are tight to and the rear wheel is 'fully' in the dropouts.

 

[dan_bo]

Nip up your cable tension whilst youre at it. Nowt worse than a saggy line.