Delayed rear shifting - already checked the usual stuff

[Bodhbh]

I was hoping to get my winter commuter running smoothly around now, but there's a nagging problem with the rear shifting...

It's a 9x3 speed deore setup with trigger shifters. The problem is the gear change will be delayed a long time after I shift - sometimes a few seconds, sometimes minutes later, sometimes never. This is the same both for up and down shifts. If I want to reliably go up or down a gear at the time I make a shift, I have to double shift, but I may get a shift further down the line. So for I have check/tried:

- changed cables. I've checked for friction, seems fine, the mech moves immediately when I shift.
- indexing, fiddled around with it a fair bit, no improvement. In fact it seems good, with no noise or jumping.
- chain length seems fine - if anything maybe a tad short - agewise prolly a couple 1000 miles on it, same as the rest of the drivetrain.
- mech lined up straight, hanger not bent
- b-adjustment screw tried at both extremes, seem a little better when it's slacked off, but it's never good.
- cassette on tight, no play there.

Any further ideas for things to try? Next step is prolly a new mech. I've not got a spare one handy to swap and check.

 

[raleighnut]

Could be the new cables need to 'harden off' and are stretching slightly, just keep at it with the indexing or stretch the cables by keeping them taut overnight, then indexing.

 

[adscrim]

How worn are your jockey wheels? How old is your cassette? How stretched is the chain?

 

[Bodhbh]

Could be the new cables need to 'harden off' and are stretching slightly, just keep at it with the indexing or stretch the cables by keeping them taut overnight, then indexing.

The new cables (Goodridge no less!) have been in a fortnight now although I've not left them taut overnight.

How worn are your jockey wheels? How old is your cassette? How stretched is the chain?

The jockey wheels are okay and not sharktoothed yet. I think both the cassette and chain have done 2-3k miles, so I'd think they're okay but I've not measured chain stretch.

 

[MisterStan]

Have you cleaned the rear derailleur properly including the springs and hinges?

 

[Bodhbh]

Have you cleaned the rear derailleur properly including the springs and hinges?

No, although - from memory - it doesn't look too bad and there's no rust. I will probably do this next, then swap it out if it does no good.

 

[MisterStan]

No, although - from memory - it doesn't look too bad and there's no rust. I will probably do this next, then swap it out if it does no good.

Not preaching, but I often find dirt causes trouble!

 

[screenman]

How did you check rear mech alignment?

 

[zacklaws]

When you changed the cables, did you also change the outers at the same time along with the caps (or what ever their called), they can get grooved or full of muck causing the cable to stick.

I had lots of problems of late downward shifting on my cross bike, even after I fitted new cables and outers, I knew it had to be the cable, because after I shifted down, I would grab the cable by hand and give it a pull, the result would be an instant gear change. When I took every thing apart again as I had identified the sticking cable as happening at the shifter end and inside the first length of outer cable. When I removed the cable, I discovered it had a small kink in it, either caused when I fitted it or has it been like it when I bought it. Fitting a new cable solved the problem.

What I suggest is, stick the bike on a stand and change gear and look to see if the cable is freeing up and also give it a tug by hand when you change at see at what point the gear changes.

And also check how much cable movement their is at the rear mech when you change up, it could be possible that you have a loose cable

I wrote all the above before really reading the original post to what the problem really was, and rather than delete it, left it as it may be usefull...................

But, I have also had exactly the same problems on one of my road bikes just recently and it drove me loopy as I could not find what was wrong, my shifting changed from day to day with a different modus operandi. After weeks I noticed the mech did not look like it was sitting correctly in the hanger and looked slightly off angle to the cassette so I stripped everything down and rebuilt it all, their was an improvement, but not perfect. My next step was to play with my indexing, tightning the cable up all the time and that solved the problem apart for not being able to get the smallest sprocket, but that was resolved by just altering the "H" screw and everything is perfect now.

Another cause which makes the gearing act strange is a bent hanger and it only has to be slightly and not easily seen, which I have had in the past, but is similar to what I have just had with the mech not seated correctly

 

[Globalti]

Did you change the outer cable at the rear derailleur? They wear and get clogged with rust and crud and delay shifting.

Also consider some better jockey wheels; I was having endless problems with my rear derailleur and had tried everything, without much improvement. One day I spotted some alloy jockey wheels with proper sealed bearings at my LBS and the owner knocked off 50% for me (they were £40, which was why they weren't selling). This has made a massive difference to the speed and accuracy of the shifting and for the moment, I'm happy.

 

[KneesUp]

I have this on my bike - I know why mine does it but I haven't got around to fixing it

In my case it's because I've left the bar end shifters loose when I fitted them so I could slide them out when I put the bar tape on. However, it's been a few weeks now ... Anyway, when I go over bumps the shifters sometimes come out a bit and it seems this is enough to mess up the gearing. If I poke them back in it's fine.

Not sure what the equivalent would be with trigger shift though.

 

[Bodhbh]

How did you check rear mech alignment?

By a quick visual it looks straight. I need to sit it by a bike with decent shifting and compare side by side tho. An now you mention it, there's a little side to side play, but not loads. Need to compare that with a good bike too.

Another cause which makes the gearing act strange is a bent hanger and it only has to be slightly and not easily seen, which I have had in the past, but is similar to what I have just had with the mech not seated correctly

Like I say, things look straight enough, but I've not ruled it out. I'll shell out for one to try if everything else fails.

Did you change the outer cable at the rear derailleur? They wear and get clogged with rust and crud and delay shifting...
Also consider some better jockey wheels; I was having endless problems with my rear derailleur and had tried everything, without much improvement. One day I spotted some alloy jockey wheels with proper sealed bearings at my LBS and the owner knocked off 50% for me (they were £40, which was why they weren't selling). This has made a massive difference to the speed and accuracy of the shifting and for the moment, I'm happy.

Yep I changed the cable at the rear mech, and gave it a fairly generous loop to avoid a sharp bend. Regarding shelling money out on better jockey wheels, well it's a difficult call - it'll get a good trashing over winter and don't really want to spend anything beyondn the miniumum to keep it running smoothly and the commute as pleasant as poss over the sh***y months. That said, the drip drip drip bad shifting drives me nuts in the end, not to mention the face plant potential when honking.

Cheers all, a few new things to try before throwing money at it.

 

[roadrash]

another tip to try , under your bottom bracket lube the cable and guides , that area is a muck magnet

 

[T.M.H.N.E.T]

My guess would be cable compression holding the minute amount of slack created by up shifting temporarily

 

[zacklaws]

Yep I changed the cable at the rear mech,
.

But what about the outer cable at the front end, they all wear, it could stick anywhere and not just at the mech, when you change down and nothing happens, give the cable a tug near the mech to free it, it may only be a millimetre or two that it is sticking and that is enough to delay changing and if the gear change happens when you tug it, it solves the problem. When mine was sticking and got bad, every gear change with the shifter, I would have to tug my cable running along the top tube to get the mech to change or wait for it to free itself.

Is the cable fitted to the mech correctly? I had a problem with SRAM once where my shifting was sometimes "cack" and I was always indexing it, then it would go out again. One day, I had my bike upside down and noticed a groove in the mech, it turned out the cable should run along it. What was happening was, when I took my wheel out, the mech would go slack and the cable come out of the groove, and when I put the wheel back in, sometimes the cable would go back into the groove but most times, it would not and then screw up all my changes. Drove me mad it did.

I'm not sure, but their maybe an optimum length for cable outers, I read something about it somewhere.

When you get a problem like this, unless you can identify the cause, you can be chasing the goal posts and barking up the wrong tree when in fact it is something simple, ie alter your indexing to improve down shifts, but that affects upshifts, so you index again to improve upshifts and you just go round in circles