Delayed rear shifting - already checked the usual stuff

[boydj]

I had similar with drop-bar brake/shift levers. Turned out the levers were not tight enough and moving slightly, knocking the indexing out. Could there be a similar issue if your 'triggers' are not sufficiently tight? Or could the outer cables not be properly seated and moving?

 

[confusedcyclist]

I have a similar problem with my 8 speed Shimano Acera rear mech and agree it's driving me nuts too. I despise riding it for that reason! I have tried changing gear cables (outer and inner), re-indexing, taking the whole thing apart and cleaning and rebuilding but still no luck. I suspect the hanger or the derailluer is damaged, it's a not my pride and joy bike so I can't justify faffing around with it for hours so I've given up, its going to the LBS this week.

 

[screenman]

Rear mech alignment is or should be the first place to start when setting up gears. This cannot be done by eye.

 

[mrandmrspoves]

I think Zacklaws may be right with his suggestion that your cable may not be connected correctly at the mech. A dirty or sticky cable may be slow to release and subsequently drop into a higher gear after a delay - but unless really in a bad way changing down would normally be rapid. The fact that you can't get it right going up or down points to incorrect routing of the cable at the mechanism clamp. It could be another mech fault or a bent hanger - but check the above carefully first. Most clamp plates have a small groove to indicate the correct clamping position, but otherwise look on line for the service diagram for your particular derailleur.

 

[Bodhbh]

Rear mech alignment is or should be the first place to start when setting up gears. This cannot be done by eye.

I have a sneaking suspicion you are right on it being an aligement issue. I remembered I was having problems along these lines a long time back and checking the paper trail and ordered a a new dropout for this bike in 2009.

Cheers all for the suggestions. I won't have a chance to get to the bottom of it now for a several weeks (nowhere inside to fettle the bike at night in the week, and away the next few weekends). I'll post again when I've worked out what hell it was in the end.

 

[DWiggy]

Check play in jockey wheels, the top one of mine was badly worn with excessive side to side play once change indexing was back to normal (I had changed everything apart from derailleur to figure this out) . Note there should be some side to side play but only a couple of mm

 

[boydj]

Another thing to check would be the length of the last section of outer cable going into the mech. If this is too short, then the bend in the cable will be tight enough to cause some drag.

 

[Shut Up Legs]

Another thing to check would be the length of the last section of outer cable going into the mech. If this is too short, then the bend in the cable will be tight enough to cause some drag.

I changed the cable at the rear mech, and gave it a fairly generous loop to avoid a sharp bend

 

[Bodhbh]

Okay, I managed to dig up a spare rear mech and swap it out. That's everything that's been swapped out pertaining to rear shifting, including the gear hanger. The problem is still there, although less so with this new mech.

So...it's an issue with a bent frame effecting the mech alignment? It's an alu frame, I guess I have to suck it up if so.

 

[Gravity Aided]

Might try a new mech , unlesss the spare rear mech is already quite new. It may save the day, a new mech, and if it doesn't, than it may be useful as a backup for the new frame/bike, or part of the new build, if that becomes necessary.

 

[mrandmrspoves]

If you don't have a replaceable hanger, I would strongly recommend that you take the bike to a good cycle repair shop as to get things spot on you need a hanger alignment tool. Without the tool you are likely to experience gear change difficulties and if you keep trying to make adjustments to the hanger you will weaken it to the point where it will keep bending or just snap off. You can buy an alignment tool and do it yourself - but you're unlikely to use the tool enough to save money on getting it repaired. I have an alignment tool and it is an easy fix. The tool screws into the frame instead of the derailleur and then the tool is set so that the indicator point touches the wheel rim at the 12 O'clock position. Then the 6 O'clock position, 3 O'clock and 9 O'clock. This will ensure the hanger is straight on every plain - as long as your rear wheel is true.