Gear adjustments

[Twilkes]

My rear derailleur is showing the following symptoms:

* doesn't want to go down to the smallest cog, no resistance from the cable and mech seems to move fine

* won't go onto largest cog without a big thumb push, as if the cable is stretching, or there is some resistance against move the mech this far.

* slow to move to a smaller cog from a larger one - it will move maybe 1-2 seconds after changing gear

* skips/jumps inbetween gears in the middle of the cogset - it's 8-speed, and generally have problems in gears 5 and 6. 4 and 7 seem to behave a lot better. I don't think it's worn cogs/chain as they were all replaced about 800 miles ago and I'd like to think they'd last a bit longer than that.

The gearing was fine until I had to fix two punctures in the last two weeks, and the problem started after the first wheel refit, and got worse after the second. I've tried adjusting the alignment barrel, but there doesn't seem to be anywhere where it's shifting smoothly in both directions.

Attached photo of the derailleur in case it is bent/damaged, but I don't think so from looking at it by eye. (nb the photo makes my bike look like something dredged up from the Titanic, but it's actually spotless)

Is there a Dr Drivetrain that can help?

 

[jim55]

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watch this

 

[HovR]

I'd start by making sure your quick release is done up nice and tight, and the wheel is sitting straight in the dropouts (especially if your dropouts are horizontal). Remember you won't be able to (or will struggle to) break a quick release with hand pressure alone, so really tighten it down.

You say that there is no resistance from the cable, are you sure of this? The only real way to check this is to put significant slack in the cable (by either undoing the anchor bolt, or putting the chain in the big cog, shifter in position for the small cog and unhooking the cable from the cable stops) and try sliding the cable outer over the inner. It should be nice and smooth.

If the issue were the cables, this would tie in with you not being able to adjust the barrel adjuster to get it shifting smoothly in both directions correctly, and it not being able to go in to the smallest cog.

If the issue isn't the cables, then two of the adjustment screws need some minor adjustment.

To get it shifting in to the big cog I'd suggest that you need to unscrew the low-stop screw (there will be two screws within close proximity to each other, the low stop is the one marked with a "L"). Turn it only half turns at a time until you are able to change in to the big cog.

To get the gears shifting in to smaller cogs smoothly you will need to loosen off the cable tension slightly, by turning the adjuster barrel (the adjuster the cables goes in to) clockwise. Again, only half turns at a time are needed.

The above assumes that there is nothing mechanically wrong with your drivechain. If you've had an off recently or hit your derailleur on something then a bent derailleur hanger could also cause the troubles shifting in to smaller cogs that you are experiencing.

HTH!

 

[boydj]

If the wheel is square & snug in the drop-outs, then the likeliest problem is with the cable, since the adjustment of the limit screws is unlikely to have changed. Change the gears to get the chain on the smallest cog, then detach the cable. Holding some tension on the cable with your fingers, move the shifter up and down the gears to see if the cable is moving freely. I had similar symptoms and the problem was caused by the cable fraying inside the shifter.

If it's not the cable, then you may need to take the mech off and give it a good clean and lube as it may jjust be a build-up of dirt and a lack of lube in the mech that's causing the problem. The mech takes a pounding in bad weather, so there's no harm in taking it off to get it properly cleaned.

 

[accountantpete]

Firstly turn the bike up and using the adjuster make sure that the chain is being presented central to the sprockets.

ATM you can see that the sprocket is touching the left of the chain in the pic.

 

[oilyormo]

i had the exact same problem and i found that the only solution for me was a new chain. after checking everthing, adjustment, stops, cable, i found that the chain was that worn that it would run for a bit at an angle after shifting before it would change, sometimes quite unexpectedly. new chain sorted it instantly. not saying this is tthe prob with yours but worth looking into

 

[Peteaud]

If it has happened since a wheel removal it would take the wheel off, ensure the seating area is clean etc and replace the wheel checking all is well before playing with the rear mech.

 

[Twilkes]

I reset the wheel, but will now have another go making sure it's sat in properly - I'm pretty sure it runs parallel to the brake pads in the exact way it used to.

I checked that the mech moves properly - it moves up and down smoothly, and there doesn't seem to be any sticking of the cable.

Now sometimes it takes a while to shift up to a bigger cog, and when I shift back down it takes a while to shift back down to the smaller cog - it seems like the chain is 'sticking' to the cog it's on and REALLY doesn't want to move. Is this a cleaning/lubricating thing?

I don't mind it taking a few seconds to shift up/down, as long as it doesn't skip once I'm in gear. There's only four journeys left until holidays anyway, so if it can last that long I'll take it to bits in the garden and kick it repeatedly until it works.

 

[betty swollocks]

If the wheel is in properly, it's likely that your problems are caused by one or both of the following:-
a) sticking inner cable wire, in which case replace it
b) poorly adjusted rear derailleur cable tension, in which case, re-adjust after having watched the video posted above.
Good luck.

 

[Twilkes]

Think I've finally laid this ghost to rest, in possibly not the correct order over the last 4 months:

replace gear cable
lubricate gear levers
replace chain
replace rear cassette, tightening hub
replace derailleur, adjusting hanger in the process - this seemed to solve the problem almost entirely
replace chain after last one had a link arm snap (prob lack of lube) - skipping problem returns
remove a chain link after checking for correct chain length
lots and lots of oil

There's still probably going to be a slight problem when the lube runs low, but it only seems to be at one end of the cassette at a time - e.g. if gears 5-8 index correctly, by the time it gets up to 3 and 4 it can skip or not change properly. It's as if there's a tiny error in each gear change, that gets multiplied up over a number of changes so it starts to cause problems. Anyone experienced this? From what I've read, if you set up the indexing for one gear the rest are meant to fall into place...