poor shift quality

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poor shift quality

Postby jules21 » Sat May 17, 2014 1:07 pm

i can't figure out the cause of poor shift quality on the rear shifters/cassette of my MTB.

it shifts up (i.e. down onto the smaller cogs OK), but to shift down (onto the bigger cogs) i need to double shift then go back up one.

- i've replaced and cleaned the cable and housings (cleaned numerous times). they seem to slide freely in their housings.
- i've replaced the shifter mechanism (Deore 9 spd thumbshift), thinking that the teeth on the old one was worn (which it seemed to be - but no improvement).
- there don't appear to be any tight corners in the cabling/housing.
- the derailleur appears to move freely, the clearance (b-screw adjustment) is tight and the cage is aligned OK.

maybe there's still gunk in the cable housing that's hidden in there? it's been pretty ordinary weather a couple of weeks ago.

i also bought some cheap plastic cable housing ends off E-bay, the bits that the join the housing to the cable boss on the frame. OEM ones are usually metal. could this be a problem? i'm struggling to see how they could compress enough to take up the shifting action - or maybe they can?

any ideas? :oops:
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by BNA » Sat May 17, 2014 9:03 pm

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Re: poor shift quality

Postby KGB » Sat May 17, 2014 9:03 pm

You don't mention how old the system is or how many km's its done. Is the cassette worn? It WILL make a difference. The derailleur may move smoothly but extra slop can develop in tvs pivots as it wears.

Even with the above, if it shifts fine one way but not the other then it should either be a problem with friction on the cable or a return spring in the derailleur that has gone soft.
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Re: poor shift quality

Postby foo on patrol » Sat May 17, 2014 9:50 pm

It could be that your cable housing is worn! :wink: My shift change on the bottom half of the cluster (yes I'm old school) could be worn as this was my problem. I got new inner and outers and my changes are good. :D The out casing wears,which in turns means some free play with the cables. :idea:

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Re: poor shift quality

Postby ironhanglider » Sat May 17, 2014 10:28 pm

Do you have exposed inner cables under the BB? It is a good place to get gummed up with sports drinks, mud etc.

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Re: poor shift quality

Postby rangersac » Sat May 17, 2014 10:39 pm

Sounds like you've covered the usual cable and housing suspects. Aside from a worn RD, I'd be checking the hanger, and then the derailleur pulley cage aren't bent. I had virtually the same issue as you a while ago and it turned out to be a bent pulley cage
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Re: poor shift quality

Postby Duck! » Sun May 18, 2014 11:01 am

Also check the derailleur pulleys, especially the top one (it's not called the Guide Pulley for nothing). If the bushings are worn it will tend to rock and not pull the chain across the gears. There should be a small amount of "float", but not excessive. Tooth wear can have some effect, but less than bushing wear.
I had a thought, but it got run over as it crossed my mind.
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Re: poor shift quality

Postby OnTrackZeD » Sun May 18, 2014 6:16 pm

jules21 wrote:i can't figure out the cause of poor shift quality on the rear shifters/cassette of my MTB.

it shifts up (i.e. down onto the smaller cogs OK), but to shift down (onto the bigger cogs) i need to double shift then go back up one.



rangersac wrote:Sounds like you've covered the usual cable and housing suspects. Aside from a worn RD, I'd be checking the hanger, and then the derailleur pulley cage aren't bent. I had virtually the same issue as you a while ago and it turned out to be a bent pulley cage



I had the very same issue and it turned out to be a misaligned derailleur hanger.
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Re: poor shift quality

Postby jules21 » Sun May 18, 2014 9:18 pm

Duck! wrote:Also check the derailleur pulleys, especially the top one (it's not called the Guide Pulley for nothing). If the bushings are worn it will tend to rock and not pull the chain across the gears. There should be a small amount of "float", but not excessive. Tooth wear can have some effect, but less than bushing wear.

bingo! thanks Duck and everyone else for suggestions. a new pulley seems to have done it - i think. i will see tomorrow on my commute.
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Re: poor shift quality

Postby AndyRevill » Tue Jul 15, 2014 5:39 pm

Hi all,

Thought I'd resurrect this thread rather than start a new one. I've just started experiencing a similar problem on the road bike (Ultegra 6700), upshifting (small to large) is fine but going the other way sometimes works sometimes not (doesn't even try) and I end up having to double shift down. I'm still using the OEM cables/outers (labelled Jagwire L3) and I've only done about 1700km, mostly in the dry though it is Tassie so plenty of gear shifts. I've fiddled and twiddled but can't get anywhere. I've even started completely from scratch following three different videos but I always end up with good upshift, poor down shift - I'm sure it's not supposed to be this hard. I relaxed the cable and moved the housing at the derailleur so I could give the cable a wipe but that hasn't helped. Given it's low age, I'm struggling to believe it's the derailleur so I'm thinking it's friction somewhere back towards the levers.

So my question is, is it worth/feasible pulling the cable all the way out and giving it a good clean and seeing if that helps or given I'm sure the OEM stuff isn't ultra high quality, should I just bite the bullet and buy some Shimano PTFE coated cables/outers?

All suggestions gratefully received, it's driving me mad :(

Andy
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Re: poor shift quality

Postby Duck! » Tue Jul 15, 2014 8:38 pm

Almost certainly the cable. Undo it from the derailleur then shift into low gear (going to bigger sprockets is actually downshifting, 'cos you're reducing the gear ratio), and roll the rubber shifter hood forward away from the bar so you can get to the "back door" on the inboard side of the hood, held in by a small phillips-head screw. Remove the screw and the cover plate & push the cable out. You'll soon find any stray strands of broken cable.

When feeding in a new cable, move the shifter out to high gear (you'll probably need to roll the hood back slightly to allow the lever to swing properly) then feed the cable in through the entry hole on the underside of the hood (you can't go in through the back door, 'cos it's damn near impossible to get the cable to go around the corner inside the shifter). Use a Teflon/PTFE-coated inner cable; non-coated ones are too draggy in the already draggy 6700 system.
I had a thought, but it got run over as it crossed my mind.
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Re: poor shift quality

Postby trailgumby » Tue Jul 15, 2014 8:47 pm

If it's not a frayed cable it's almost certainly a bent hanger or contaminated housing (cable outer). Hangersbare easy enough to straighten Cleaning cable housing never works. New outer is the only cure.
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Re: poor shift quality

Postby AndyRevill » Tue Jul 15, 2014 9:08 pm

Duck! wrote:going to bigger sprockets is actually downshifting, 'cos you're reducing the gear ratio).


That was my instinct but then I saw several references using the opposite terminology (I presume referring to the sprocket size) - just shows I should stick with my instinct and not believe everything (anything?) you read on the web, except here of course :D

Thanks for the help, I'll get myself some new cables and outers. I've seen a couple of places also selling Shimano polymer coated cables (for 6800) - not sure what the difference is (PTFE is a polymer so maybe nothing) any idea if they're significantly better?

Thanks again, Andy
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Re: poor shift quality

Postby Duck! » Tue Jul 15, 2014 9:18 pm

Don't know exactly what the stuff on the 9000/6800 cables is, but it's supposedly slipperier than PTFE. "Polymer" is a very broad term, so it could be anything. I have found that it tends to go all fluffy, which then clogs the outers, so in the longer run I don't think they're as good as the 7900/6700 cables. Aside from that there's no problem with compatibility.
I had a thought, but it got run over as it crossed my mind.
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Re: poor shift quality

Postby AndyRevill » Tue Jul 15, 2014 9:27 pm

Duck! wrote:Don't know exactly what the stuff on the 9000/6800 cables is, but it's supposedly slipperier than PTFE. "Polymer" is a very broad term, so it could be anything. I have found that it tends to go all fluffy, which then clogs the outers, so in the longer run I don't think they're as good as the 7900/6700 cables. Aside from that there's no problem with compatibility.


I'll stick with PTFE for now then!

Thanks again for the help

Andy
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Re: poor shift quality

Postby Dragster1 » Tue Jul 15, 2014 9:39 pm

I run a 9 speed Deore shifter with a rapid rise xt derailleur, when it get sluggish its always a bent hanger or the cable outer where it goes into the derailleur. When you ride in the rain the wheel seams to flick water onto the inner cable and it dribbles down along your inner with grime and finds its way in the outer.
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Re: poor shift quality

Postby tez001 » Thu Jul 17, 2014 5:45 pm

I had a similar issue, albeit I could still shift, but it felt the shift was a bit stiff / hard.
Changed out the original Jagwire stuff for regular Shimano SS stuff.

A combination of new outers and inners, proper cable routing and correct outer length has improved the shifts dramatically.

Dont always just cut the new outers to the same length. Spend a bit of time and get the correct outer length too as well as routing the cable.
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Re: poor shift quality

Postby AndyRevill » Mon Jul 21, 2014 6:56 pm

Thought I'd give a quick follow-up. Over the weekend I replaced front and back inners and outers with Shimano PTFE coated ones. I've been worried about cable rub on the head tube so also took the opportunity to look at routing and decided to change to using cables crossing under the down tube. Looks way better at the front and shifting is back to its best :D

Now, if I could find a way to do something better with the rear brake cable (apart from swapping sides) life would be Rosie.

Cheers, Andy
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