Ideas for things to try please.

Bike is 09 Meta 5.5
New drivetrain fitted as follows:
New 22/36 Deore rings on existing SLX cranks.
New XT 11/34 cassette
New KMCX9 chain
New BBB pulleys

Main pivot bearings recently replaced. No play in swingarm or rear hub (Pro2)

Blackspire stinger cured the problem when I’d experienced similar previously. It’s still in place but no longer appears to be curing the problem.

Running out of ideas.
Will B-tension make a difference?

Chain too long?

DBW, nope not chain length. If anything I run them quite tight.
Plenty of spring tension in rear mech too

Could try a larger granny ring…I swapped to a 26t from a 22t on my chainset (Double with 36t…Both deore steel rings) on my bike as I found I was dropping the chain. Not had a problem on previous setups with a double with 36t & 22t…wondered if it could be the SLX front mech.

How long have you been running them?
Maybe it might need a bit of time to ‘gel’/wear together?

Though are you running a medium length mech or a full length one? Which I think is going back to Dave’s comments about the chain being too long??

Hmm, Nuke, I’m reluctant to loose the lower gearing.
I’m dropping the chain from the 36 ring, straight over the 22 and onto the BB shell, so I don’t think this is it. Thanks anyway.

Roller on the stinger worn?

butter fingers? 😉

front mech set up?

Zippy, drivetrain was done about 4 dry rides ago (25 – 30 milers)
Only a couple of rides since doing pivot bearings. Had expected this to cure it TBH.
Long cage XT mech.

I’m hoping it’s just a bedding-in thing too.

Ha, is my problem the recent lack of Peaks/Calderdale grinding paste? 😆

Where about is it dropping?

Just pedalling along, and it falls off the granny?

When downshifting?

Upshifting, and it falls off the other end?

Woody, roller on stinger is still good. Bearing stripped and greased too

TJ, front mech has been focus of my attention so far. Will keep tweaking limit adjusters but am fairly happy that I’ve got it right.
Mech height is OK.

xiphon,

Loosing from 36t inwards, over the 22t and onto BB shell, when rattling down long rocky descents.
Shifting is crisp & accurate.

Is your front mech vertically down far enough the seat tube? Should be 1-2mm gap between the bottom of the front mech, and the largest chainring (or bash in your case?)

1000s of people have the same bash/36/22 combination as you, without any issues.

Take it to a LBS, sounds like a 5 min job for someone.

Will re-check front mech all-round but am fairly confident that I’ve got it adjusted fine.
That’s prompted a thought – I haven’t checked for wear in the pivots of the front mech or alignment around (rather than up-down)the down-tube.

[video]http://www.youtube.com/watch?v=ngm6dr-1na0[/video]

From what ET describes, loosing the chain inwards over rocky descents, then chain tension needs looking at.
Fit a DCD and take us back to the 1990s.

missingfrontallobe,
Chain tension would be my assumption too.
Whilst there’s plenty of spring in the rear mech, I think I’ll strip it and lube it up just in case its not picking up the slack quick enough.

Got a few more ideas there – thanks folks

OK, think I’m onto something now re chain tension…
I noticed last night that the bearings in Pro2 rear hub are no longer buttery smooth. I think they may be “notchy” enough in the freehub to introduce some minor pulsing in chain tension.

Will replace/rebuild and see if that fixes the problem.
Thanks for the input.

Check your jockey wheels are running smoothly at the same time. My lower jockey was sticking and causing slack in the top run of the chain particularly when doing the 1/4 turn back pedal into a turn.