Issues with Shimano 2x11 gear changes

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yelfordrover
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Issues with Shimano 2x11 gear changes

Post by yelfordrover »

Can anyone shed any light on a problem I'm having with a 2x11 set-up on a flat bar road bike?

I'm using a Shimano M4120 rear mech with M5100 trigger shifter, allegedly compatible. I'm using a Miche 12-32 cassette and a double 40-24 chainset.

I can't get it to shift from the 12-13 on the cassette although the other gears are OK. Increase the cable tension & it will shift fine but then it will be very slow (or impossible) in shifting back up the cassettte from the 32 to the higher gears. Have adjusted the B screw to get a close gap between the cassette 32 and the 24 chainring. Have also tried lots of gap but didn't help with the problem.

Any suggestions as to what I'm doing wrong?
slowster
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Re: Issues with Shimano 2x11 gear changes

Post by slowster »

Suggest you look at the Park Tool guidance, i.e. https://www.parktool.com/en-int/blog/re ... leshooting.

The two things I would check first are the cables, e.g. especially making sure that the cut ends of the outer are clean and square with no exposed wire strands, and the derailleur hanger. The former is straightforward, but the latter requires an appropriate tool or taking the bike to a shop mechanic.
peetee
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Re: Issues with Shimano 2x11 gear changes

Post by peetee »

I agree with slowster. It sounds very much like an outer cable compression issue. On the smallest sprocket there is little to no tension in the cable. As the lever is clicked up the outer cable sections come under compression and the shifter is unable to pull the inner enough to perform one cog of movement. The cable outers are designed not to shrink but this only happens if the ends are cut perpendicular and finished flat. Without perfect ends the cable can compress as only some of the reinforcement strands take all the strain or the sharp ends dig into the end caps. This invariably happens at the first click up as beyond this the outer cable shrinks no further and the mech follows the shifter more-or-less exactly.
Last edited by peetee on 29 Dec 2022, 11:24am, edited 1 time in total.
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yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

Thanks both for the speedy response.

I've checked the rear mech hanger and it's spot on.

I will try an experiment with a very short section of outer cable with the trigger fixed to a piece of hand held tubing about 30cm from the rear mech and see if that overcomes the problem.

The frame unfortunately has internal cable routing so there is a very long run of outer cable which won't help matters. I've thought of converting to external cable runs by riveting on some cable stops (it's a carbon frame); just a bit reluctant about drilling the frame.

I'll let you know how I get on.
peetee
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Re: Issues with Shimano 2x11 gear changes

Post by peetee »

There’s nothing wrong with a single continuous outer running internally. In some respects it’s better than several outer pieces. What messes things up usually is the way it’s routed. No cable likes tight bends or sudden deviations and installation can be really troublesome on some frames. If I were you I would start by removing the clamp bolt at the mech and trying to create enough slack that the end caps of the outer can be removed to inspect the outer cable ends.
The older I get the more I’m inclined to act my shoe size, not my age.
yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

An update after some experimenting.

With the Shimano set up, tried a new very short length of outer (not fixed to the frame) with no bends in it. Still got the same problem; ie if I set enough cable tension to go from the 12-13 then it doesn't want to drop the chain from the 32-29 and also other upshifts.

Swapped the whole system to a Sram Rival WiFLi 11 speed rear mech and Sram Apex 1 11 speed trigger, all taken off another bike. Now absolutely no problems with the shifting in any direction.

The other interesting detail relates to B screw setting. The Shimano rear mech has a 41 capacity (my set up is a 36 range). With the B screw set to be as close as possible between the 32 and the upper pulley, then I've got chain slack in the 24x12,13 and 14. The Sram rear mech has a 37 capacity and with the same B screw setup there is no chain slack on any rear cog.

I do wonder if it is the Miche cassette that is causing the problem as I imagine that the Shimano one has a more complex ramping system. The Sram mechs always seem less finicky to set up and so are likely to be able to cope with the simpler casette.

Anything else I can try?
peetee
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Re: Issues with Shimano 2x11 gear changes

Post by peetee »

Can you provide a photo of the pulley wheel to 12t cog gap on the problem gearset please?
The older I get the more I’m inclined to act my shoe size, not my age.
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531colin
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Re: Issues with Shimano 2x11 gear changes

Post by 531colin »

yelfordrover wrote: 9 Dec 2022, 1:14pm ................
Swapped the whole system to a Sram Rival WiFLi 11 speed rear mech and Sram Apex 1 11 speed trigger, all taken off another bike. Now absolutely no problems with the shifting in any direction............
Is this because Sram pulls more cable per shift?
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531colin
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Re: Issues with Shimano 2x11 gear changes

Post by 531colin »

peetee wrote: 8 Dec 2022, 8:14pm ...........On the smallest sprocket there is little to no tension in the cable. As the lever is clicked up the outer cable sections come under compression and the shifter is unable to pull the inner enough to perform one cog of movement. The cable outlets are designed not to shrink but this only happens if the ends are cut perpendicular and finished flat. Without perfect ends the cable can compress as only some of the reinforcement strands take all the strain or the sharp ends dig into the end caps. This invariably happens at the first click up as beyond this the outer cable shrinks no further and the mech follows the shifter more-or-less exactly.
You know, I've been messing about with bikes for most of a lifetime, and thats the clearest statement of this problem that I've seen!

Bearing in mind cautionary tales about Grandmothers and Eggs, is this point worth making?..........
For a shift made by increasing cable tension it all works best if you keep some tension on the shifter until the shift is complete, because there is an "overshift" built into the shifter, before the pawl drops back into the ratchet..
For a shift made by decreasing the cable tension you only need to poke the shifter so the pawl releases, there is no "overshift" in this direction.
Have the top gear limit screw backed off as much as possible (without overshooting the sprocket, obviously), to give the longest possible cable pull for that shift.
TheBomber
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Re: Issues with Shimano 2x11 gear changes

Post by TheBomber »

531colin wrote: 9 Dec 2022, 6:13pm
You know, I've been messing about with bikes for most of a lifetime, and thats the clearest statement of this problem that I've seen!
Likewise I think it may cover issues with indexing I’ve had going back to 6 speed.

For the OP: are Shimano 11 speed levers compatible with 12t up? I thought they were only speced for 11t up? And re alternative brand cassettes - I have a 10 speed Sram cassette that everybody tells me should be compatible with my 10 speed levers but it also doesn’t work, again at shifting the first couple of sprockets. I replaced with an Ultegra which works.
cyclop
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Re: Issues with Shimano 2x11 gear changes

Post by cyclop »

yelfordrover wrote: 9 Dec 2022, 9:25am Thanks both for the speedy response.

I've checked the rear mech hanger and it's spot on.

I will try an experiment with a very short section of outer cable with the trigger fixed to a piece of hand held tubing about 30cm from the rear mech and see if that overcomes the problem.

The frame unfortunately has internal cable routing so there is a very long run of outer cable which won't help matters. I've thought of converting to external cable runs by riveting on some cable stops (it's a carbon frame); just a bit reluctant about drilling the frame.

I'll let you know how I get on.
My full suspension off roader has always had full outers and have been faultless but,and this may be significant,they are 9spd.The cables are external,running in guides built into the frame.Above 9 spd is where incompatabilities start to set in.
yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

peetee wrote: 9 Dec 2022, 5:04pm Can you provide a photo of the pulley wheel to 12t cog gap on the problem gearset please?
I've taken a photo but just struggling with sending it! My default position for the B screw was to get as close a gap as possible between the 32 cog and upper pulley when on the 24 small ring.
yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

531colin wrote: 9 Dec 2022, 6:04pm
yelfordrover wrote: 9 Dec 2022, 1:14pm ................
Swapped the whole system to a Sram Rival WiFLi 11 speed rear mech and Sram Apex 1 11 speed trigger, all taken off another bike. Now absolutely no problems with the shifting in any direction............
Is this because Sram pulls more cable per shift?
I certainly think this could be the reason why Sram is much less finicky than Shimano.
yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

531colin wrote: 9 Dec 2022, 6:13pm
peetee wrote: 8 Dec 2022, 8:14pm ...........On the smallest sprocket there is little to no tension in the cable. As the lever is clicked up the outer cable sections come under compression and the shifter is unable to pull the inner enough to perform one cog of movement. The cable outlets are designed not to shrink but this only happens if the ends are cut perpendicular and finished flat. Without perfect ends the cable can compress as only some of the reinforcement strands take all the strain or the sharp ends dig into the end caps. This invariably happens at the first click up as beyond this the outer cable shrinks no further and the mech follows the shifter more-or-less exactly.
You know, I've been messing about with bikes for most of a lifetime, and thats the clearest statement of this problem that I've seen!

Bearing in mind cautionary tales about Grandmothers and Eggs, is this point worth making?..........
For a shift made by increasing cable tension it all works best if you keep some tension on the shifter until the shift is complete, because there is an "overshift" built into the shifter, before the pawl drops back into the ratchet..
For a shift made by decreasing the cable tension you only need to poke the shifter so the pawl releases, there is no "overshift" in this direction.
Have the top gear limit screw backed off as much as possible (without overshooting the sprocket, obviously), to give the longest possible cable pull for that shift.
I can just get a shift from the 12-13 by keeping tension on the shifter and being very patient. Re having the top gear limit screw backed off as much as possible, I thought the opposite would be better to give more cable pull?
yelfordrover
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Re: Issues with Shimano 2x11 gear changes

Post by yelfordrover »

TheBomber wrote: 9 Dec 2022, 9:22pm
531colin wrote: 9 Dec 2022, 6:13pm
You know, I've been messing about with bikes for most of a lifetime, and thats the clearest statement of this problem that I've seen!
Likewise I think it may cover issues with indexing I’ve had going back to 6 speed.

For the OP: are Shimano 11 speed levers compatible with 12t up? I thought they were only speced for 11t up? And re alternative brand cassettes - I have a 10 speed Sram cassette that everybody tells me should be compatible with my 10 speed levers but it also doesn’t work, again at shifting the first couple of sprockets. I replaced with an Ultegra which works.
I wouldn't have thought that an 11 or 12 would make any difference, but you never know. Interesting to hear that your Sram cassette was giving problems. Could point to my Miche causing my issues, even though it is fine with Sram shifter & mech.
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