one gear slippling!

[mythste]

I'm going crazy.

My third highest gear keeps slipping once every 3 or 4 rotations. the chain will come off the rear casette for hald a turn, then re-engage.

Driving. Me. Crazy.

All other gears appear to be bob on which leads me to believe indexing and upper/lower limits should be fine. This happens on both front cogs.

Anything obvious i'm missing before I turn up at my LBS with steam coming out of my ears? It's a 105 RD.

 

[mjr]

What sort of "come off"? To one side (probably a derailleur fault) or spinning in place (probably chain or cogs)? Is the chain worn? Does the sprocket look pointy?

I use my third highest gear most, so it tends to be the first to show wear faults.

 

[mythste]

What sort of "come off"? To one side (probably a derailleur fault) or spinning in place (probably chain or cogs)? Is the chain worn? Does the sprocket look pointy?

I use my third highest gear most, so it tends to be the first to show wear faults.

I honestly couldn't say, I presume its not coming off sideways else I'd feel another gear engage and that's certainly not happening. Chain and Cassette are around 600 miles old now - frequently mickled! Certainly no points on the sprocket and its a seldom used gear - I normally commute with fully loaded panniers so getting up to that speed is a weekend only occurrence!

 

[Racing roadkill]

Check your chain for stretch. Anything between 0.5 and 0.75mm and its on its way out, anything over 1mm, and you're going to need a new chain. I use the sort of slipping you're describing, as an indicator to check the chain forthwith. I use one of these deelys to check properly.

 

[mythste]

Thanks for the input on that, though would I not notice something similar in all gears if that was the case?

600 miles seems short for a well looked after chain (though im certainly no expert - and not about to call trading standards )

 

[Broadside]

Are all the teeth present on the affected sprocket?, I have seen one missing before that leads to occasional chain slip.

 

[derrick]

Is the cassette clean, ie nothing jammed between the cogs, just a thought.

 

[Racing roadkill]

Thanks for the input on that, though would I not notice something similar in all gears if that was the case?

600 miles seems short for a well looked after chain (though im certainly no expert - and not about to call trading standards )

You'd be surprised how easy it is to knacker a chain, especially if you use all chainrings and sprockets.

 

[mythste]

You'd be surprised how easy it is to knacker a chain, especially if you use all chainrings and sprockets.

Its my first "real" bike and to be fair, I probably have been cross chaining etc a bit more than would be considered healthy - probably changing gear a bit more in general than perhaps I should have I guess! If I can't get to the bottom of it and the LBS suggest a new chain, would it be worth replacing the cassette as well? I can see an ever so slight sharking on the lowest 2 gears

 

[mythste]

Is the cassette clean, ie nothing jammed between the cogs, just a thought.

Good thought, not checked, will follow up this evening!

 

[mrandmrspoves]

The fact that it occurs every 3 or 4 revolutions should be a clue....look very carefully at your chain. If the problem was the sprocket the problem would occur every revolution. The fact that the problem only occurs on one sprocket may make you think the problem is specific to the sprocket but my guess is it isn't the problem. Rotate your chain backwards very slowly while looking carefully at the bottom of the rear derailleur and look for any evidence of the chain sticking as it goes through the jockey wheels. If this does not reveal a problem shift onto your largest chain ring and with your eyes looking along the chain from chain ring to the back of the bike slowly rotate it backwards again looking for any lack of uniformity.

 

[Racing roadkill]

Its my first "real" bike and to be fair, I probably have been cross chaining etc a bit more than would be considered healthy - probably changing gear a bit more in general than perhaps I should have I guess! If I can't get to the bottom of it and the LBS suggest a new chain, would it be worth replacing the cassette as well? I can see an ever so slight sharking on the lowest 2 gears

If the sprockets in the cassette are okay, and the cassette is torqued up to about 40Nm, then I personally wouldn't change it, if it's only done 600 odd miles.

 

[mythste]

The fact that it occurs every 3 or 4 revolutions should be a clue....look very carefully at your chain. If the problem was the sprocket the problem would occur every revolution. The fact that the problem only occurs on one sprocket may make you think the problem is specific to the sprocket but my guess is it isn't the problem. Rotate your chain backwards very slowly while looking carefully at the bottom of the rear derailleur and look for any evidence of the chain sticking as it goes through the jockey wheels. If this does not reveal a problem shift onto your largest chain ring and with your eyes looking along the chain from chain ring to the back of the bike slowly rotate it backwards again looking for any lack of uniformity.

I'll give this a try and report back - thanks!

 

[raleighnut]

The fact that it occurs every 3 or 4 revolutions should be a clue....look very carefully at your chain. If the problem was the sprocket the problem would occur every revolution. The fact that the problem only occurs on one sprocket may make you think the problem is specific to the sprocket but my guess is it isn't the problem. Rotate your chain backwards very slowly while looking carefully at the bottom of the rear derailleur and look for any evidence of the chain sticking as it goes through the jockey wheels. If this does not reveal a problem shift onto your largest chain ring and with your eyes looking along the chain from chain ring to the back of the bike slowly rotate it backwards again looking for any lack of uniformity.

Could easily be a 'stiff' link in the chain.

 

[screenman]

Not saying this is your problem but worth reading.

A rear derailleur hanger is the small tab of metal that connects your rear derailleur to your frame. It is designed to be the weak link so that it breaks first and saves other more expensive parts from failure. Almost all hangers are specific to the model of bike you are riding and even vary year to year. It is a good idea to have a spare one on hand instead of trying to track one down when you really need it (like the night before a race).
It’s not too often that I don’t feel the need to check the alignment of a rear derailleur hanger. It is also a rare occurrence that a hanger doesn't need aligning, they are almost always out of spec. Even brand new hangers purchased to replace bent old ones frequently will not match up perfectly with the frame and will need aligning.
Most of the time it is not visible to the eye if a hanger is bent or not. Telltale symptoms of a misaligned hanger - the rear derailleur will shift fine at one end of the cassette but will lose it’s ability to shift and hold a gear as it moves from one side of the gear cluster to the other. If your hanger is way out of whack your derailleur will appear to be pitched on a sideways angle as you eyeball it from the back of the bike.
No matter how fancy you get with your other adjustments, your rear shifting will never function normally unless you have an aligned hanger. That is why performing this alignment is usually one of the first tasks I do when adjusting a rear derailleur. There is no point in fine tuning all of the other adjustments only to have to do it all over again once the hanger is shifted into alignment.

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