Derailleur skipping

[Smiler1968]

OK, I’ve been riding my mountain bike for a number of years without any real maintenance other than a wash every now and then. When I eventually found time to give it some TLC I noticed a few things. There was some movement in the bottom bracket. That’s been swapped out for a new hollow tech BB. The 1% chain checker dropped straight through. I’ve changed that to a 9 speed SRAM (971 I think). I have a Shimano cassette (not sure which one) and an XT rear mech. I know the SRAM works as I run that on my commuter. I have changed the rear gear cable and straightened the mech hanger. The gears are just not crisp. If I get them right going up the gears they hesitate coming down. I’m thinking the chain wore out the cassette although it doesn’t look too bad. I’ve got it where I could just about live with it (we are off camping soon so want to take the bike for family bimbles). When in the stand it just about goes up and down the gears. However when I ride it, it still goes up and down the gears but the hanger jumps and flicks like it’s catching on something. As I said it doesn’t do it in the stand only when I’m riding it. I’ve taken the jockey wheels out and cleaned them but it’s still doing it. Any ideas?


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[Brucey]

you don't say clearly that you have replaced the cassette or not, or what you mean by 'hanger skipping' either. The hanger is the part of the frame that the mech is bolted onto; it normally does not move.

If you have not changed the cassette a new chain is bound to jump (or skip) on it when you pedal hard, if the old chain was worn to over 1%.

The sluggish gear changing is somewhat symptomatic of a bad gear cable, and/or a worn upper pulley in the rear mech. Index systems are somewhat sensitive to the exact type of cable inner and housing that are used as well as the type of lubrication, the cable prep, and a load of other things besides.

cheers

[Smiler1968]

you don't say clearly that you have replaced the cassette or not, or what you mean by 'hanger skipping' either. The hanger is the part of the frame that the mech is bolted onto; it normally does not move.

If you have not changed the cassette a new chain is bound to jump (or skip) on it when you pedal hard, if the old chain was worn to over 1%.

The sluggish gear changing is somewhat symptomatic of a bad gear cable, and/or a worn upper pulley in the rear mech. Index systems are somewhat sensitive to the exact type of cable inner and housing that are used as well as the type of lubrication, the cable prep, and a load of other things besides.

cheers

Sorry, I’ve used the wrong terminology. The rear mech is skipping. It pullls forward and releases flicking backwards as I cycle. Almost as if the pulley wheels are binding. And no I’ve not changed the cassette yet. The chain does not skip on the cassette.

I have noticed that the flicking only occurs in the middle ring of the chainset. The outer ring and the granny ring run OK. I thought it might be a bent tooth on the middle ring but I can’t see anything obvious although it is looking a bit worn.

The skipping occurs in every gear of the cassette when I’m in the middle chain ring.

Does that make sense?


I'm a trendy consumer. Just look at my iPad using hovercraft full of eels.

[Brucey]

yes that makes sense to me. It tells me that almost certainly the middle chainring is worn (teeth either burred or hooked) and you are probably getting a mild case of chainsuck, where the (new) chain wants to stay attached to the chainring and doesn't release at the bottom.

If it happens regardless of load the teeth are probably burred sideways (or bent perhaps) and it ought to happen on the workstand, but if it only occurs under load it is probably hooked teeth. I have fettled chainrings into shape using a file before now with some success but if you don't fancy that a new chainring should sort it out.

cheers

[Smiler1968]

yes that makes sense to me. It tells me that almost certainly the middle chainring is worn (teeth either burred or hooked) and you are probably getting a mild case of chainsuck, where the (new) chain wants to stay attached to the chainring and doesn't release at the bottom.

If it happens regardless of load the teeth are probably burred sideways (or bent perhaps) and it ought to happen on the workstand, but if it only occurs under load it is probably hooked teeth. I have fettled chainrings into shape using a file before now with some success but if you don't fancy that a new chainring should sort it out.

cheers

Chainsuck. What a great word. I’ll replace the middle chainring and see how that goes.

Thanks.


I'm a trendy consumer. Just look at my iPad using hovercraft full of eels.

[foxyrider]

Do the cassette while you're at it - will save you time in the long run, it almost certainly is worn and the symptoms are being disguised by the chainsuck issue.

[Smiler1968]

Do the cassette while you're at it - will save you time in the long run, it almost certainly is worn and the symptoms are being disguised by the chainsuck issue.

Yes I think I’ll have to bite the bullet and get a new one.


I'm a trendy consumer. Just look at my iPad using hovercraft full of eels.

[Smiler1968]

Yep, chainsuck it was. I’ve put a new cassette and new middle chainring on and it’s like new again.

Thanks for the help.


I'm a trendy consumer. Just look at my iPad using hovercraft full of eels.