Cable pull

[tykeboy2003]

Can anyone help me with my rear derailleur problem?

I have an Edinburgh Cycles Country Explorer which has a 3 x 9 speed (Shimano Alivio/Acera) drivetrain and recently the rear indexing has deteroriated to the point where hardly any of the changes are smooth and/or instant. Often I'll have to index twice to get a gear change.

So far I have eliminated the following:-

Chain/cassette wear - both replaced
Bent hanger - I bought an alignment tool and the hanger is straight.
Cable - replaced.
Cable outers - all replaced.

In addition I have thoroughly cleaned and lubricated both the derailleur and the shifter.

Today I measured the cable pull in each position and it seems that the pull varies from 1.8mm between the lowest 2 gears (biggest sprockets) and 2.9mm between the two highest gears and a graph of values is not a bad fit for a straight line. Is that normal?

[Brucey]

some things to check

- that you have the cable mounted in the pinch bolt correctly
- that the rear mech isn't worn out
- that the chain and sprocket isn't worn out

etc etc

but my money is on the cables; they need to be perfect, so proper SIS housing (not spiral wound stuff), properly prepped, the correct ferrules, proper polished stainless inners, all lubed up properly (not no lube, not thick lube)...

The cable pull measurements you report are anomalous IMHO, and probably indicate a cable fault of some kind.

cheers

[tykeboy2003]

Thanks Brucey, but the bike is only 3 and a half years old (done about 5000 miles on it) so I'd be very disappointed if the derailleur was worn out, and as I said I've replaced the chain and cassette.

When you say the cable pull measurements are anomalous, do you mean that each gear change should be the same pull? I suppose that if I measured the pull at the shifter and it was different, then that would confirm that its the cables?

[Brucey]

do check, but from memory the cable pulls are not quite as you have found.

I suppose that if I measured the pull at the shifter and it was different, then that would confirm that its the cables?

I'd have said so, yes.

cheers

[karlt]

Check the cable routing. If it's not going into the mech the right way the pull can be all over the shop.

[tykeboy2003]

Check the cable routing. If it's not going into the mech the right way the pull can be all over the shop

I'm pretty sure there's nothing wrong with the routing, I've been fettling bikes for nearly 50 years.

Mind you I've never had a problem like this before. I think that the 9-speed is part of the problem, I noticed that the new Edinburgh Cycles touring bike equivalent has gone back to an 8-speed cassette. The sprocket spacing is just that little bid wider with 8-speed or less making the setup far less critical.

[Brucey]

BTW, it might be disappointing for a rear mech to wear out in 5000 miles but it can certainly happen.

Once a mech gets a bit baggy good indexing can be somewhat elusive, so check for play in the mech, play in the top pulley etc, and if you come up empty on the cables/housing , I'd suggest that you just bung another rear mech on and see if that made a difference or not.

cheers

[jk49]

I'm not sure about this, but I think I remember that a rear mech I set up once had two options for connecting the inner cable to the pinch bolt. one way for 7/8 speed and a slightly different way for nine speed. Perhaps one was over the pinch bolt and one was under. It might be worth trying to get the tech doc off the interweb and checking...... Or this might be a load of old nonsense, in which case apologies and someone shoot me down quick!

[tykeboy2003]

I've measured the cable pull at the shifter, and taken the average of four measurements for each position.

pull per gear change

3.36 (largest sprocket to next)
2.84
2.67
2.62
2.28
2.32
2.28
2.41 (to smallest sprocket)

Mean pull

2.60mm

I'd sort of expect the two extreme pulls to be bigger than the rest, as you can limit the movement by the end stop adjustments on the derailleur. So I think the shifter looks to be ok.

Brucey, I'll have a really good look at the mech for signs of wear.

Jk49, I'm sure I have always connected the cable to the mech in exactly the same was as when the bike was new.

[tykeboy2003]

Brucey, I checked the jockey wheels and there was a lot of play, particularly on the top one. I've replaced them and shifting is much better now - at least when changing to a larger sprocket. Changing to a smaller sprocket is still very hit-and-miss.

When I operate the gears without the chain, the top jockey wheel appears to be well aligned across all the sprockets.

Any more good ideas?

[Brucey]

If the pulleys were worn then it is quite possible that the other pivots in the mech are worn too.

Getting the mech to align with the sprockets is encouraging, but doesn't guarantee swift shifting; for that the mech needs to be relatively rigid and should be moving with a fair amount of force. Lazy upshifts often suggest a slightly draggy cable to me, as do the previous cable pull measurements (the ones at the shifter are pretty much what I'd expect).

cheers

[jk49]

ok, how about drag or roughness on the little saddle the cable pivots round under the bb shell. Sorry I don't know the name of this. Maybe some crud or tar spot on this?

[Manc33]

Not unless the cable is visibly wearing into the plastic there getting stuck in a groove.

I would just throw a £20-£30 used Saint M810-GS rear mech on it and have done with it. Those mechs are switchable between close ratio and mountain, it has the shadow design, it has that "direct cable routing", it has a metal cage (unlike the carbon cage of the M972 which is a hideous price and not built as solidly).

Or keep buying brand new £20-£30 rear derailleurs that develop play.

I never once got decent shifting from Acera/Altus/Claris level shifters, or mechs. It was rough straight out of the box and only got rougher.

[Mick F]

If the pulleys were worn then it is quite possible that the other pivots in the mech are worn too.

My vote is for the top pivot being worn. The pivot where it bolts to the dropout.

I'll bet that the mech has play in and out that can be seen in the top pivot.

I'll also bet that the mech changes gear sweetly if you remove the cable and push the mech in and out manually.

[tykeboy2003]

My vote is for the top pivot being worn. The pivot where it bolts to the dropout.

Mick, I think you're right, there is a bit of in-out play in that pivot. I guess a new derailleur is required.