Chain Slipping In Rear Derailleur

[HormyAJP]

Hi all,

I ride a Ridgeback Horizon tourer - so effectively a road bike - with 8 speed read casette and Shimano gears. I recently had problems with my chain slipping slightly at the back. After investigation I realised that it was because one of the links in my chain had frozen. This made sense as the slipping was at regular intervals, very brief and only when I put higher tension on the chain.

I replaced my chain last night and very pleased with myself set off this morning. The problem has changed and got much worse. Now when I put anything other than the lightest pressure on the pedals the chain slips but but a large amount, i.e. it seems to only stop when my crank has reached the lowest point (this is different to before when the slip was very brief and clearly linked to the defective chain link). The chain isn't slipping on the cassette, just the derailleur, specifically the lower two small cogs (from what I can tell).

I have guesses at what the problem is but wanted to check before I shell out more cash. Firstly is it possible that I've put the wrong type of chain on the bike? The chain was "Oxford Standard" and looked identical to my last. Also I made sure I had the same chain length (in links) as before. Are there chain types that don't work well on road bikes?

My main suspicion is that the lower of the two small derailleur cogs is worn. Looking at the teeth they seem to be noticably shorter than the ones on the other cog. It wouldn't surprise me that under high tension the chain would just slip over these. Is this likely? My natural reaction is to think it's this, but I'm just surprised that this wasn't happening before (maybe my old chain was so gunked up that it just didn't slip?!). It's possible I've knackered the cog by cycling with the knackered chain. I ran the bike for about a week and a half with the minor slipping. Are the cogs this easy to damage.

Oh, and can the small cog be replaced (looks like it)?

Any insight would be appreciated before I go buying a whole new gear set

Cheers,
Andrew

 

[chillyuk]

The little cogs you refer to are the jockey wheels. It is not unusual for one to be a different shape on the teeth to the other. Your problem is almost certainly the cassette.

 

[HormyAJP]

The little cogs you refer to are the jockey wheels. It is not unusual for one to be a different shape on the teeth to the other. Your problem is almost certainly the cassette.

Thanks chillyuk. Having kept my eye on the back wheel when it's happening it looks like the chain doesn't slip on the cassette, which is what's confusing me. Looks like the chain is gripping nicely on the cassette and it also doesn't matter which cog it's on. Also seems strange that it's just started happening with the new chain.

 

[chillyuk]

I'm a bit old fashioned and am only reall au fait with older type freewheels. I am not sure of the terminology but the part that fits on the hub and onto which the cassette fixes can fail (as can the hub) and this would allow the whole lot to slip. I cannot offer any more suggestions because as I said I am not up to date.


Just a thought, I assume it IS the back end where it is slipping and not on your front chainwheel.

 

[HormyAJP]

I'm a bit old fashioned and am only reall au fait with older type freewheels. I am not sure of the terminology but the part that fits on the hub and onto which the cassette fixes can fail (as can the hub) and this would allow the whole lot to slip. I cannot offer any more suggestions because as I said I am not up to date.


Just a thought, I assume it IS the back end where it is slipping and not on your front chainwheel.

It's definitely not the hub as I recently replaced my back wheel (and hub) and that's all nice and tight. And there's no way of the cassette to slip if the hub's fine.

Yes, back end for sure.

 

[amaferanga]

It could be the pawls on the freehub are sticking. Can happen on any hub - new or old - if it's defective or the grease is too tacky.

 

[zexel]

It's definitely not the hub as I recently replaced my back wheel (and hub) and that's all nice and tight. And there's no way of the cassette to slip if the hub's fine.

Yes, back end for sure.

Not true.

As amaferanga has said brand new hubs can suffer from this too, depending what grease is on the pawls.

Depending on what hub you have you could try some (not a lot!) WD40-a-like stuff in the back of the hub (between the hub and spokes not in the bearings) while turning the hub. It has worked for me in the past. Obviously it depends on the type of pawl system you hub has.

Edit: Your issue does sound like new chain/old cassette interface issues.

 

[PpPete]

Worn teeth on the jockey wheels are not going to cause the gears to slip in the way you describe....might affect the changing, but those wheels are free to turn so "slipping" on them is irrelevant.

I've never heard of an "Oxford Standard" chain though. You need to get one that is specific to the number of speeds on the cassette. Any 8 speed chain will do.

And don't put WD-40 anywhere near your hub.

Do you still have the old chain? Lay it out flat - and measure it the length of 12 links. to the nearest 1/16 th of an inch. My bet is the old chain had stretched, and that will have affected the cassette, even if you cant see it.

 

[Enigma2008]

This is almost certainly due to wear and tear on the cassette. Not necessarily the length of time you've had the chain/cassette pairing but how much cycling you have actually done on that pairing. With th old chain freezing up it's sounds like a fair bit!

The chain and cassette wear together over time with the chain gradually wearing the teeth of the cassette. You replaced the chain and the new chain doesn't fit the worn cassette, the solution is a new cassette I'm afraid.

The jockey wheels (upper and lower are different) will also be worn but should function with a new chain, however, I would also replace these, Tacx do sealed bearing replacements that are compatible with the popular types of rear mechs.

Sorry but it means another £40+ or so!!

 

[John the Monkey]

Do you still have the old chain? Lay it out flat - and measure it the length of 12 links. to the nearest 1/16 th of an inch. My bet is the old chain had stretched, and that will have affected the cassette, even if you cant see it.

That'd be my bet too.

Sheldon Brown's page on chain maintenance has some visual checks you can do.

http://sheldonbrown.com/chains.html#wear

 

[al-fresco]

I hate bloody derailleurs - they're so simple - just cable tension, upper and lower delimiter screws - why are they such awkward little sods to adjust properly? And why, after you faff about with them for days, do they suddenly start behaving as soon as your LBS points a screwdriver in their direction? I mean - come on - it's just not fair!

 

[amaferanga]

If its not slipping on the cassette then it still sounds like a freehub issue to me, especially since it apparently happens in all gears.

If it is slipping on the cassette then it's almost certainly the wrong chain (Oxford standard - what's that then?) or worn cassette with a new chain that's the problem.

 

[youngoldbloke]

Thanks chillyuk. Having kept my eye on the back wheel when it's happening it looks like the chain doesn't slip on the cassette, which is what's confusing me. Looks like the chain is gripping nicely on the cassette and it also doesn't matter which cog it's on. Also seems strange that it's just started happening with the new chain.

- that is just when you would expect it to happen. As others have said it is likely that there is some wear on the cassette. You could try putting the old chain back on - flex it from side to side to loosen the link - and see if it still happens as before.

 

[HormyAJP]

Thanks for the replies folks. I'm not going to be at home for a few days so won't be able to investigate further, but when I do I'll be sure to get back.

Cheers,
Andrew

 

[HormyAJP]

Hey all, I'm back!

So you were all indeed correct, it was in fact the cassette that was worn. On closer inspection I could clearly see that the teeth were very non-uniform and the dips were no longer that pronounced. Once I knew what I was looking for I managed to find a quite road and observe the chain slipping over the cassette without managing to kill myself!

I got a new cassette for £25 (thankfully my setup was cheaper than most due to ratios on the back), along with the tools, and fitted it in the shop. Annoyingly they couldn't lend me the tools due to insurance and health and safety and all that, but the guy was incredibly helpful and let me sit in a corner off the shop floor to fit the cassette.

Sadly I got about 3m out of the shop and the chain slipped again. On closer inspection it turned out that the front middle cog was also badly worn and needed replacing. Another £25 later and my bike finally appears to be back to full health! I'm amazed how much the front cogs cost given how little material they're made from. Glad you don't have to replace things too often.

On that note though the manager - who I would stress wasn't sales pitching me and was very knowledgeable and generally a nice guy - was saying that you should replace your chain/cassette roughly every year (obviously usage dependent, he suggested 2500miles). He reckoned if you change your chain at just the right time, 6 months or so in, then you can squeeze an extra few months out of your cassette. Also told me about a cheap chain testing tool to check if your chain is overly worn. Anyway, all interesting stuff and useful to know. I'd certainly got away lightly as I've had my bike around 4 years and done 5000 miles+ and never changed chain or cassette (probably why it all went bang when the chain was replaced).

Thanks for all the help and suggestions. I love cycle maintenance, the learning curve never seems to stop . Oh and good link "John the Monkey", that was pretty informative too.

Cheers,
Andrew