New chain/cassette/cable slipping under load

toby1kenobi

Hi there,

I've just replaced the cable for the front derailleur as well as the chain and cassette. Foolishly I disposed of old chain before fitting the new one (which broke), so I sized the replacement as per the, "Chain Sizing - Largest Cog and Largest Chainring Method" method described here:

http://www.parktool.com/blog/repair-hel ... gth-sizing

All seemed to go well, but the chain is now slipping under load. For example trying to accelerate quickly, on the flat, in mid to high gears the chain jumps. It tends to happen once and feels like quite a big movement. I'm not 100% sure where it jumps - I'd assumed at the rear, but once when it happened the chain jumped down to a smaller sprocket on the front, so maybe it's happening there?

After replacing the cable I setup the front derailleur as per this video:

http://bicycletutor.com/adjust-front-derailer/

It seemed to go ok, and I can switch between all (3) sprockets. I can also get all gears with the rear derailleur without problem (the hanger's not bent).

Anyone got any tips for what might be wrong? Any help would be much appreciated.

Toby

vinnn

You need new chainrings.
Sounds like you probably left it too long to replace your chain. It would have not only worn away the teeth on the cassette but the chainrings too.

toby1kenobi

Thanks for responding - The bike's less than two years old and used for commuting (100km/week at most), is that likely do you think?

Toby

toby1kenobi

PS Presumably I could test by seeing if it happens on the less used chainrings?

dennisn

Was the chain slipping BEFORE you replaced cable, chain, and cassette? If it wasn't
then I suggest that YOU have done something wrong. I doubt that you need new chainrings after less than two years unless you have never oiled anything. Have you kept things well oiled? Hate to say it but this has all the earmarks of a not so good bit of bike tuning up and / or lack of regular maintainence.

Blue Meanie

+1 dennisn

Chainrings rarely slip, is normally the rear. Checking your indexing for the rear mech.

New Chain fitted with Snap-Link / Hyper Link / Pin? If it's a pin it you may have a stiff link.

Worn Bushes on the rear mech can't make even the best set-up mech misbehave, as with jockey wheels.

Good Luck

toby1kenobi

Thanks for your 'help' Dennis, really constructive! Maybe something lost in translation, but the accusatory tone plus lack of any concrete advice is hard to beat.

I do keep the chain and gears clean and oiled (although it's a constant battle commuting in London throughout the year) and the chain wasn't slipping before it broke. I'm certainly not saying that I've set it up perfectly, but everything looks fine and I have no problems switching gears (indexing seems fine, hanger's nice and straight).

Blue Meanie, it's an SRAM chain with a master link - I did check for stiff links, but I'll have another look this evening and also check the bushings/jockey wheels.

Thanks for your help,

Toby

dkcrooby

Hi, thought I would add something in too.
Do you have a full suspension bike? If so, when measuring the chain they recommend you fully compress the rear shock or you will end up with too much slack - this from my experience leads to chain slip at full-load (hard pedalling when standing etc.) when on the smaller chainrings. I normally remove an extra link to solve the problem, as I haven't the tools to lower the compression, and it solves the problem.
If you have a hardtail, the only possible cause is a loose or worn jockey wheel on the rear derailleur. It it is at an angle it can't align the chain correctly - or you have incorrectly measured the chain (which I doubt because you seem to know what you are talking about).

Hope this helps,

Craig

toby1kenobi

Craig,

Thanks for taking an interest, unfortunately I have a hybrid, so no suspension!

Thanks again,

Toby

dennisn

toby1kenobi wrote:

Thanks for your 'help' Dennis, really constructive! Maybe something lost in translation, but the accusatory tone plus lack of any concrete advice is hard to beat.

Sorry if I sounded "accusatory", but you put new parts on a bike and they don't work.
I would say that if it doesn't work after all this new stuff that it has a 99.999% chance of being installer error. As for concrete advise, well, since I have no idea what you've done wrong "concrete' advise" is not something anyone can give you except to take it to the shop and let them find out what's wrong.

toby1kenobi

dennisn wrote:

Sorry if I sounded "accusatory", but you put new parts on a bike and they don't work.
I would say that if it doesn't work after all this new stuff that it has a 99.999% chance of being installer error. As for concrete advise, well, since I have no idea what you've done wrong "concrete' advise" is not something anyone can give you except to take it to the shop and let them find out what's wrong.

No worries, I've had worse. I did asks for tips though, your response didn't offer anything other than an implication of incompetence, which was of no help at all.

toby1kenobi

vinnn wrote:

You need new chainrings.
Sounds like you probably left it too long to replace your chain. It would have not only worn away the teeth on the cassette but the chainrings too.

You might have been on to something - I can't get it to slip on either of the other chainrings, only the middle one (which gets used the most by far). That could be because there's not enough resistance on the smallest, or because I'm too puny to provide enough force on the largest, but at the moment I don't have a better explanation than the one you provided - so thank you!

Toby

toby1kenobi

toby1kenobi wrote:

vinnn wrote:

You need new chainrings.
Sounds like you probably left it too long to replace your chain. It would have not only worn away the teeth on the cassette but the chainrings too.

You might have been on to something - I can't get it to slip on either of the other chainrings, only the middle one (which gets used the most by far). That could be because there's not enough resistance on the smallest, or because I'm too puny to provide enough force on the largest, but at the moment I don't have a better explanation than the one you provided - so thank you!

Toby

A final follow up - it was indeed the middle chainring, so thanks vinnn for suggesting that!

The Rookie

In which case, if you have an alloy chainring it would be worth trying to use the larger chainring (and larger rear gear) more in the future to balance out the pedalling loads and by using larger gears both ends you'll get reduced wear anyway.

Simon