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Shimano rear shifter clicks twice but only shifts once when going to larger cogs

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Shimano rear shifter clicks twice but only shifts once when going to larger cogs

Old 07-17-13, 06:29 AM
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Shimano rear shifter clicks twice but only shifts once when going to larger cogs

I'm having a slightly annoying issue with my Ultegra rear shifter. Around the middle of the cassette, often when I want to jump up 2 easier cogs, I'll push the lever 2 clicks, but the chain will only move up 1 cog. I then have to click the smaller shift lever to cancel out the mis-shift (at this point clicking the smaller lever doesn't move the chain back down to a smaller cog, it just puts the alignment back into the right position I think).

I can move up each cog individually with single clicks but the issue comes up when I try to double click in the middle of the cassette. On the stand the bike shifts well but I've noticed that I have to make sure my lever shifts are very precise (didn't used to be an issue). Not enough push against the lever and it will not shift the chain up the cassette and too much push when I shift obviously clicks the lever more than once.

Could this be due to sticky cables? Worn shifters? I think I noticed this happening when I replaced my inner shifter cables a few months ago so I don't know if that's the issue.

Thanks for any advice!
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Old 07-17-13, 08:09 AM
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There is cable stretch which causes the cable to be slack. The first click takes up the slack, the second click actually pulls up the chain to the next cog.

The solution is to shift the gears to the smallest cog, loosen the cables with a 5mm allen key, then pull the cable tight with a pair of pliers and while holding on to the cable tension, tighten the cable with the 5mm allen key.

Once that is done, try shifting the gears one at a time, if it doesn't go up, increase the tension with the barrel adjuster. If it goes up two gears with one click, then loosen the tension with the barrel adjuster.

Last edited by TiBikeGuy; 07-17-13 at 08:15 AM.
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Old 07-17-13, 10:06 AM
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It could be as simple as your trim being slightly biased outboard. This would be confirmed if shifting to smaller sprockets was consistently better than shifting up.

OTOH, the single biggest cause of erratic shifting, including what you describe id cable friction, especially in the rear loop. The sharp curve there sees the fastest wear of the liner, and causes the highest friction. Also there's often poor alignment where the housing enters the adjuster which causes added binding.

Without seeing it it's impossible to confirm the cause, but one indicator is if shifting to larger sprockets seems to require more force on the lever than you remember.

Other possible causes include RD being too high (B-screw setting) and wear on the upper pulley, if an older derailleur.
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Old 07-17-13, 10:13 AM
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There is no such thing as cable stretch. Housing compresses and ferrules get completely seated on housing and the end result is a loose cable, but cables do not stretch. The OP's problems occurs in the middle of the cassette, so the slack you're talking about has obviously been taken up. My guesses include old/dirty/worn housing, or possibly a derailleur hanger that is not aligned properly. It could be a shifter problem, but that is less likely.
To the OP, if your cables/housing are more than a few months old, just replacing the cables will get you nowhere. All of the wear that affects shifting takes place in the housing, which you did not replace.
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Old 07-17-13, 10:21 AM
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Originally Posted by cxwrench View Post
There is no such thing as cable stretch.
+1,
I avoid all discussions about whether cables stretch or not, since the effects of cable stretch, housing compression, and/or settling of the fittings are all the same as if cables stretched.

However, cable stretch would affect trim all the way through the range, and this doesn't seem to be the case,except if the trim is only slightly off, which is easier to check and adjust before taking anything apart.
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Old 07-17-13, 11:28 AM
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Originally Posted by cxwrench View Post
There is no such thing as cable stretch. Housing compresses and ferrules get completely seated on housing and the end result is a loose cable, but cables do not stretch. The OP's problems occurs in the middle of the cassette, so the slack you're talking about has obviously been taken up. My guesses include old/dirty/worn housing, or possibly a derailleur hanger that is not aligned properly. It could be a shifter problem, but that is less likely.
To the OP, if your cables/housing are more than a few months old, just replacing the cables will get you nowhere. All of the wear that affects shifting takes place in the housing, which you did not replace.
I see. I replaced my cables a few months ago, but not my housings and the housings are a year old. So maybe a full housing and cable replacement is needed?

Thanks for the advice.
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Old 07-17-13, 01:51 PM
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Cable stretch is like chain stretch. They don't, but we know what you mean.
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Old 07-17-13, 02:09 PM
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Originally Posted by Syncmaster View Post
I see. I replaced my cables a few months ago, but not my housings and the housings are a year old. So maybe a full housing and cable replacement is needed?

Thanks for the advice.
1 year is not old. Check the adjustment suggestions others mentioned.
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Old 07-17-13, 08:45 PM
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Originally Posted by Homebrew01 View Post
1 year is not old. Check the adjustment suggestions others mentioned.
If the OP rides a lot...let's say 4-5 days a week, 1 year is old. What would you recommend for a cable/housing change interval?
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Old 07-17-13, 08:53 PM
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Originally Posted by cxwrench View Post
If the OP rides a lot...let's say 4-5 days a week, 1 year is old. What would you recommend for a cable/housing change interval?
I don't think of intervals in time or miles.

There are too many variables since the issue isn't how far or how long you've been riding but how often you shift. Someone in Kansas might have housings last until the UV gets to the plastic, while someone riding the roller coaster hills of Connecticut is lucky if the rear loop lasts a year.

So if/when you feel you need more strength to downshift, suspect cable friction and replace the housing. One test I use is to remove the wheel and pull the wire away from the downtube like a bow string. This gives a good sense of how much friction there is. Of course, it helps to have done this test with a new cable and housing so you have a baseline.
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