hazzak

My rear derailleur isn't shifting very consistently, particularly across the smaller 5 cogs on the 10 speed cassette. What I've tried so far

- checked rear hanger alignment with Park Tools alignment tool as well as removing it and checking it on a flat surface
- new inner cable and checked it was moving smoothly through all the housing
- cleaned rear derailleur and made sure it was moving smoothly
- checked wheel alignment and that the cassette was tight on the wheel
- adjusted cable tension but can only get either reliable shifting up or reliable shifting down but not both


I'm running out of ideas for what could be causing my shifting problems. I've managed to get it to the point where it shifts through most gears apart from a couple of the middle cogs where I need to move the shifter until it clicks and then give it a little extra nudge, before it gets to the second click, to encourage it to shift up.

By the process of elimination, assuming the cable and derailleur are fine then it must be the shifter, however it appears to click through all 10 positions fine both up and down. I've read about lots of cases of Shimano shifters jamming up and not clicking through at all but never of one having uneven cable pull between indexing positions?


Anyone have any other ideas as to what else it could be?

Andrew R Stewart 

The only thing left is cable casing to replace. Are the casing ends in good shape? What you describe sounds like friction issues. Is the cable run internal? How worn is the chain and cassette? When you cleaned the der did you remove the pulleys? If so it's possible to get them wrong on reinstall. Is the cable properly routed at the anchor bolt.

But I suspect cable friction. Andy.

cny-bikeman

Need some more clarity and info first.

When did the problem start, and did any incident or repair procedure precede it?

You refer to shifting "up" but that's not clear. Does the problem occur when shifting to larger or smaller cogs - or in both directions?

Is the problem the same on the large chainwheel and next smaller?

How consistent is the problem, and are there any variables you have not mentioned?

FBinNY 

Before you take up heavy drinking, try a diagnostic experiment.

Adjust the trim, so you get nice crisp down shifting (to larger sprockets). Now down shift until you get to one of those shifts that hang. Pluck the bare wire at the down tube like a guitar string (pluck hard). Do this a number of times in various problem shift situations. If it generally completes the shift after plucking, your issue is sluggish cable return via the RD return spring.

The cause could be thick lube in the housing, a worn liner - probably in the rear loop, or some other source of friction like bad alignment where the housing enters a fitting. It could also be a lever issue where internal friction is a bit high for the RD spring.

A very common cause is a rear housing loop cut short and entering the RD fitting at an angle because it's pulling upward. You can test this easily enough using a rubber band to tighten the radius or the rear loop's curve adjusting it until it enters the fitting straight on.

hazzak

I fitted a new groupset a few weeks ago and shifting was OK initially but degraded recently. When I say "up" I mean shifting to a larger cog on the cassette. I can either adjust the cable tension to shift better to smaller cogs or better to larger cogs but can't get it perfect for both.

The problem occurs ~75% of shifts over the problematic area (middle of the cassette in particular).

FBinNY 

I read the OP, and other than having up and downshifting reversed, my answer is still the same. Try the guitar string test, and see if plucking changes anything.

BTW- in the bicycle world, the terms up and downshifting are used the same as with cars. Upshift means to a higher gear, or toward a smaller rear sprocket. Not that this changes anything here.

hazzak

Apologies for the confusion. I was just clarifying for cny-bikeman. Will give the guitar string trick a go and report back with what happens.

Kimmo

This is a bike with the aero STIs, right?

Shimano is causing your shifting problems. This system isn't reliable; it requires the condition of the cable and housing to be between perfect and almost perfect. The previous 10s stuff was pushing it, and then they added friction by routing the cables under the tape without increasing cable pull, although they did change it slightly and broke compatibility.

If you really want to kick it in the arse, Ergos and a Shiftmate.

FBinNY 

Be nice. Yes, the RD spring could be stronger and assure a more consistent cable return on upshifts, but the problem isn't as bad as all that. The vase number of clients enjoy clean, crisp, and reliable shifting (as long as the housings are clean and in good shape).

OTOH, maybe Shimano is intentionally making this a bit finicky, hoping folks will move away from "unreliable" cable to electronic shifting.

digibud

The way I remember it is "up" refers to speed. Smaller rear cog, bigger front cog.

xenologer

shifting slow at middle of cassette ? compared to extremes ends?
notice cassette profile is concave towards middle ; increased gap at middle = less response

bring derailer closer to cogs
b-tension out, and check housing loop isn't too tight

techie2

Had a similar issue. I tracked mine to a neglected chain. You don't mention checking it so, have you? Mine was pretty dry but a bit of oil cleared up my shifting issues.

Joe

FBinNY 

Thanks for bringing this up. Better lubrication makes a chain more supple, and improves shifting. This is probably the easiest thing to check since it doesn't involve taking anything apart, and the chain could always use fresh lube. On my bikes I consider finicky shifting to be the first hint that it may be time to re-oil the chain.

Anoter consideration is that with wear chains become more flexible sideways and this can mean more overshift is needed for the chain to make the jump. The issue is worst when the jockey wheel sprocket distance is greatest, so it's usually felt at the small end of the cassette.

bkaapcke

Make sure the cable is connected to the correct side of the pinch bolt. It makes a big difference in shifting. bk

rpenmanparker 

That's right, just like on a car, upshifting means to a higher gear ratio, as in "high gear". You can go any speed you want though on a bike in any gear. It is the auto engine that can't accommodate a wide range of gears at different speeds.

hazzak

The chain and cassette are both pretty new (<200 miles). I've just changed the inner, outer and all ferrules which didn't improve things.

FBinNY: I've tried plucking the gear cables and it didn't seem to help with the upshifting. However, I did notice that on the problematic gears the first time I click the STI lever the rear derailleur moves by almost the correct amount (not enough to complete the shift, obviously) but if I subsequently downshift and then upshift in that position there is almost no movement of the rear derailleur. Could this be indicative of some kind of friction issue?

FBinNY 

Yes, good trim in the pulled direction and poor trim in the spring direction is a solid indicator that the cable friction is too high for the spring. Given that plucking didn't help, I suspect the likeliest source for excess friction is in the rear loop (chainstay/RD).

Take a good look at the loop, especially where it enters the RD fitting. Often loops are cut short, and end up entering the fitting at an angle rather than straight on. Or possibly it's just wear. Find a length of housing to replace, and cut it so the lead to the fitting is straight on. --- To determine the right length, I fit the loop into the RD fitting, and lead it toward the chainstay fitting, pulling forward or back until it naturally makes the turn and enters the fitting straight on. This is most obvious if you leave off any tight fitting ferrule so the housing is free to leave at an angle.

fietsbob

Die drawn cables are a big improvement, because they are slicker on the outside surface..

the die flattens the outside of the cable.

hazzak

I've tried replacing the rear loop with a longer piece of housing that gives a straighter entry into the derailleur and that didn't help. If it was purely a friction problem would there not be shifting issues across the whole cassette?

Also, is it reasonable to assume that if the shifter is clicking through each position properly then it isn't malfunctioning? Has anyone experience unreliable shifting over just a few gears as a result of a faulty Shimano STI lever?

FBinNY 

Sometimes mechanical issues just need a fresh pair of eyes. If you list your area of residence, someone might be able to refer to a skilled mechanic who might spot something not obvious over the net.

ultraman6970

What drive train is this guy talking about? How many speeds? model? etc? Bicycle type and model?

hazzak

The bike is a Cannondale CAAD5 frame with a Shimano 105 5600 10 speed groupset. The bike originally came fitted with a 9 speed 105 group and I recently changed it out for the 5600, which is what I'm currently having problems with.

I've updated the OP with some photos of the drivetrain. I noticed that the cable goes through a bit of a kink over the BB shell which might add friction, however from what I can tell it's always been like that even when the gears shifted properly.

I'm in Oxford, UK. Been working on the bike at the local bike co-op with a couple of bike mechanics and they've pretty much suggested the things that have come up in this thread.

simmonsgc

I'll just throw this one out there. I had a poorly shifting bike once. Drove me nuts. Then I noticed that a previous owner had used brake housing for the loop instead of shifter housing. Not to insult your intelligence, but just thought I'd mention it.

bradtx

hazzak, Grasping at straws here, but the jockey wheel on the RD should have a little 'wobble' to allow the chain to fall onto the cog. I have had a shifting issue in the middle of a cassette on the upshift (to a smaller cog) that depended on the RD's spring to actuate. I can only guess in my case is that is where the closest ratios were. The cause for me was too short a housing run to the RD, the housing in your photo certainly looks long enough. Your problem is on the downshift (to a larger cog) where you provide the shift pressure. Is it possible that the cable housing isn't properly seated in the STI's body? Again, grasping at straws.

Brad

Al1943

+1
If the cable is attached to the wrong side of the derailleur pinch bolt the actuation ratio will be wrong.