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Rear Derailleur Adjustment
Should be a well drained topic, still I have a niggling issue I can't seem to overcome:
I can adjust the rear derailleur either for high gear or low gear!
The gear:
Shimano XT 9 sp rapid rise from 2006
The problem:
After careful adjustment following all the how-to's and manuals I can either ride for
- "low gears", which means low gears work all great but he chain will come off very sluggishly from the 2-3 smallest cogs when shifting down. With the rapid rise this means this is the direction in which the derailleur springs push.
- "high gears", where everything works great for the high (small) gears, but the third and second gear has a tendency to cross shift on the next lower (bigger) gear. Which is somewhat annoying when climbing hills 
!
Actions so far (not necessarily to fix this issue just stuff I have done lately):
- new cassette
- new chain
- new cables (inner and outer)
What else? Or should I just accept that the derailler is done and needs replacement?
Cheers,
Volker
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The first thing I'd do is to change the cables. Failing that, it sound like your derailleur is a touch bent. This happened to an X9 of mine, and although it looked straight, when I compared it to a new one, it was ever so slightly off.
Good luck!
Done the cables, so this is a tick.
Wouldn't a bent derailleur translate into a constant offset across all gears and would therefore be adjustable through the cable length?
I forgot to mention that the two settings are only three-four clicks on the cable adjustment screws apart.
Das kommt davon wenn man im Matsch rumfährt...
Refer to Sheldon Brown, the famous german bike guru
http://sheldonbrown.com/german/derailer-adjustme...
Sheldon wasn't German. He was from Massachusets.
Otherwise your advice is good.
http://sheldonbrown.com/derailer-adjustment.html
A bent hanger will make the movement of the derailleur not parallel with the axle, which really cocks up your shifting.
That was a German joke. Let me explain this difficult topic:
http://en.wikipedia.org/wiki/German_humour
things to check.
Chain length is correct: put it in small front and small rear - does the chain sag?
Derailleur top wheel is correct distance from large and smallest cog, sometimes adjusted by a "B screw" - see the manual for your system.
Check shifter is functioning correctly - e.g. full movement, cable seating ok. (this is unlikely but worth a look)
Cable routing is correct - especially where it clamps to the rear derailleur.
Derailleur isn't bent or twisted - probably the most common if adjustemnt is correct. See http://www.parktool.com/blog/repair-help/rear-de...
Derailleur set up correctly (this from http://www.parktool.com/blog/repair-help/rear-de...)
Shimano "rapid rise" or "Low-Normal" derailleurs use a return spring that puts the derailleur under the innermost rear sprocket when the inner wire tension is released. As with other indexing derailleurs, the inner wire tension should be set as tight as possible with good shifting. However, the symptoms of a too-tight setting are different, which for "Low-Normal" systems are when the derailleur shifts outward slowly, or a there is a rattle from the upper pulley being aligned too far outward. Look underneath the rear sprocket at the alignment of the upper pulley when there is a rattle to see if this is the cause.
1.Shift chain to middle ring in front and innermost sprocket in back.
2.Pedal and shift lever one position.
3.Pedal and turn barrel adjuster counter-clockwise to tighten inner wire tension until chain begins to shift outward.
4.Turn barrel adjuster clockwise 1/4 turn until chain runs smoothly on second cog.
5.Shift outward one sprocket at a time trying each gear. Turn barrel adjuster 1/4 turn clockwise if too tight symptoms occur.
6.Shift to all other normal gear combinations and test adjustment
HTH
I like the comment on how the bent derailleur will make the shift work non-parallel to the axle, that would explain it to my engineering brain, because it basically limits the total span of the derailleur.
Cool, now I have the justification for the new derailleur I am in the process of ordering
! I'll let you know how that goes!
... did you replace the outers? I find they are usually the culprit when you have dicky shifting. Rarely is it the cable inner, unless it is frayed up near the shifter. Crud gets in, especially down by the rear derailleur
I run Low Normal XT derailleurs on both my bikes, and they are really easy to set up. Really
I've even bent the cage on one thanks to a large stick, but thanks to some appropriately applied force and a vice it has been straight and trouble free for the last 18 months or so since.
I'd also recommend Gore Ride On sealed shifter cables. Haven't had to touch the shifter adjustment or replace a section of outer on any of my bikes since fitting them at the beginning of last year, and you know the crud we've all been riding in of late.
1. SRAM derailluers are less prone to problems caused by cable flex because the cable needs to move twice as much as Shimano for a gear change.
2. Carbon derailluer cages are much better than aluminium or steel ones because they don't bend.
A DAG tool should return it to parallel.
Funny, from behind my bike looks pretty much exactly like in the parktool bend hanger example foto.
My simplistic brain confused "hanger" with "cage" though. So instead of buying a new derailleur I guess I'll need to find a LBS with an adjustment tool.
Have you set your limit screws properly to get the span right?
If its like the park tool foto then - a new hanger is relatively cheap. BUT you may want to check the drop out is not twisted. ie. the hanger is straight but the rear frame drop out is warped
I had bent my hanger pretty badly and thought that the rear mech was ok....
Turns out after bending the hanger back to what I thought was straight. and trying a new hanger..the rear mech was bent also.
Looking like I have to bend the cage or get a new rear mech.
Its an XT RD and its done well considering I have abused it so.
The new RD ordered on CRC looks exactly the same but is deore only. Hope its as good.
OK;
It seems that you have checked every thing - Except the cable clamp on the RD.
Make sure that the cable is clamped to the correct side of the clamp scew by removing the screw and clamp and seeing where the proper track for the cable is under the clamp washer.
Getting this simple thing wrong changes the leverage ratio of the RD and can make an 8sp act like a 9sp etc, and can give all the symptoms you describe.
Shimano used to have that trick in part of their bike mechanics course in NZ when I lived there.
PS - It might pay to look at the jockey wheels considering the age of the RD.
What about the jockey wheels? Thinking about what is old and what is new, I was wondering whether old and run down jockey wheels might be a contributor to the imprecission? But how so?
The cable is going down its designated path through the clamp!
Certainly from what I've seen of SRAM 9-speed RDs, they do wear out.
You could get yourself some BBB Roller Boys for Shimano RDs for about $20. They have decent quality ball races in top and bottom jockey wheels for less resistance and more shifting precision. (The top one won't fit on 9-speed SRAM RD's below X0 due to the off-centre bolt in the top pulley).
I use them as a standard upgrade so that I've got ballraces on both jockey wheels - I don't see a lot of sense in using bushes on the two parts of the drivetrain that spin the fastest, ceramic or not. Ballraces spin easier.
Did you change the cable outer?
Yep, done the outer cable!
How do these Gore RideOn Sealed cables work? Does it assume one constant full length of outer cable to go from shift lever all the way to the rear DR? On my bike this breaks up into three pieces of outer cable, and the inner cable runs open in between those. Would the Gore cables still make sense in this set up?
You don't need full length outer for Gore to work. It's a drop-in replacement for your existing setup.
It uses sections of slightly-larger-than-normal bore outer housing and ferrules that go in place of your normal outer. The teflon coated low-friction cable is covered with a full length teflon cable liner that keeps the dirt out, finished off by a neat little bellows that stops the crud entering at the derailleur end.
I ran XTR rapid rise for a few years until a couple of years ago when I switched to XX.
I found if you had limit screw adjustments right and correct cable tension then they would work perfectly even with bent cages, hangers etc. a couple of years ago I had one with lower jockey wheel about 1.5cm further from the wheel than the inner jockey wheel and it still shifted perfectly while the one on my other bike had copped the opposite hit and the outer jockey wheel was about 1cm closer to the spokes than it should have been. Both were massively out of square and shifted perfectly so I didn't bother doing anything about it.
I did find if the cable tension wasn't set right though I would get similar problems re working across a few gears only on the cassette. Solution was disconnect and re-set all adjustments again starting with inner then outer limit screws then tension which was set using middle ring and the 32/34 gear on the back.
Only thing to remember is rapid rise works in reverse so you need more cable tension (anti clockwise on the barrel adjuster) if the gears don't move sweetly towards the smaller 12 tooth gear or less tension if it's not moving properly up towards the larger 32/34 gear.
DR adjusted, love that XT!
I adjusted the DR over the weekend so that cage and DR is straight again and am back to the old precision shifting!
Thanks for all the support and hints!