Help please.. Rear derailleur issue.. Skipping in small cog

Help!

I have noticed recently that my chain is jumping when in the smallest cog. .didn’t bother fixing it for a few rides as I never really use the 11 tooth and always forget until I’m out on the bike that it’s an issue, however tonight I found some time and thought I’d address the issue.

Should be simple adjustment of the limit screw . Didn’t work. Undid the cable and reindexted.. Still no joy. Eventually I tried riding it with no cable attached to take that out the equation . Still rubbish.

The chain and cassette are less than 400 miles old and used mainly on road, and it never slips in any other gear so doubt the chain is worn.  What am I missing as its annoying me.

Ta

If DEFINITELY not an indexing, limiter issue issue you might suspect:

A tight link in chain.

A damaged tooth on the 11T

Check jockey wheels are ok

Check mech hanger is straight

Is the problem at the front, the chain line causing chain to ride a tooth/ different ring when on very outside gear

Wear, try a different chain as that’s easiest to change.

Stiff link in chain?

I thought it may be a buggered chain. .Even though its reasonably new. I will check out all your suggestions. Ta

“Jumping”. Do you mean trying to move from the small cog to the next or do you mean jumping around the cog itself?

Is your mech hanger straight? Have you checked it – with the correct tool?

Check your B screw. If there’s not enough chrain wrap then there’s a chance the chain could be slipping under pressure.

Check if there is any dirt or debris in the gap between the sprockets. The channel is quite shallow between the smallest cogs and if there is greasy grime or a twig in there the chain can ride up on it and not engage on the sprocket teeth properly.

Are you sure the cassette lockring isn’t for 12T? That would make the chsin not fully sest on the 21t sprocket.

Crikey . Not thought of any of this stuff!

First thing I’ll do will be check for a stiff link.

Scotroute. .it skips when not changing gear. Can you please expand on the b screw.  How can I tell?

Ill also check the lock ring and teeth for damage/obstruction tomorrow.

Thanks all!

Count up how many revs you turn it!

Turn the b screw out, anti clockwise obvs, one full turn at a time and see if it improves. No difference, wind back to original!

Lockring is for a 12T cassette. If it’s too big the chain doesn’t sit on the 11T properly. Do you have another wheel that you can test. That’s how I spotted it on the bike Ive just built.

TiRed…. Are the lock rings marked in anyway?

Asking for my own future reference. 🙂

It’s ten speed, worth an 11 speed lock ring.. Is that the issue

11t damages tooth which may not even look damaged. If it’s shimano you can buy a replacement 11t cog not sure about SRAM.

Another thing to check is any quick links in the chain some are uni directional and can cause skipping.