Derailleur Problem

[Jimmy Welch]

Hi everyone
My chain jumps off and locks up when I drop from large to small chainring I've attached a video of it happening but the chain ends up rubbing against the bottom of the derailleur cage I changed the chain last week but it was happening before the change the any thoughts welcome 🙏

View: https://youtube.com/shorts/ZCPEOmjyfY0?si=pinIpGcmp97DXyCu

 

[fossyant]

Chain is too long !

 

[fossyant]

You need at least 6 links out of it.

 

[fossyant]

Always measure the old chain and the new one together.

 

[raleighnut]

As @fossyant says the chain it too long, the way I measure chain length is wrap the chain around big-big not threaded through the mech then add 2 links and split the chain off at that point, by the time you've fitted a 'quicklink' you have 3 links of safety before suffering the catastrophic failure of a too short chain.

 

[Jimmy Welch]

You need at least 6 links out of it.

It was happening with the old chain is there a possibility the old chain could have stretched so far as to cause this amount of slack in the chain

 

[presta]

If all you have done is change chains, it's too long. If the rear derailleur is not the original one, it may have insufficient capacity, in which case you must check the shortened chain will still have enough length to go over the large ring and large sprocket before taking any links out.

 

[presta]

It was happening with the old chain is there a possibility the old chain could have stretched so far as to cause this amount of slack in the chain

No, either the chain's too long or the derailleur doesn't have sufficient capacity, or both.

 

[raleighnut]

It was happening with the old chain is there a possibility the old chain could have stretched so far as to cause this amount of slack in the chain

No but it's possible that the old chain was also too long

 

[Jimmy Welch]

No, either the chain's too long or the derailleur doesn't have sufficient capacity, or both.

The derailleur is about 5 chains old so I think capacity wise it's OK I'll give the link removal a go and see if it's solved

 

[presta]

The derailleur is about 5 chains old

As long as it's the original that came with the bike it should be ok, the problem may arise if it's been changed since. Just be careful to check you're not removing too many links before you remove them, or it'll do a lot of damage it's too short.

 

[Jimmy Welch]

View: https://youtube.com/shorts/AEvA4Kg_vUI?si=eQRJwrk9KMw2JtbB

5 links removed jobs a goodn thanks everyone

 

[fossyant]

View: https://youtube.com/shorts/AEvA4Kg_vUI?si=eQRJwrk9KMw2JtbB

5 links removed jobs a goodn thanks everyone

Technically 6 as you can't do odd on a chain. I win within 2 minutes of the original post. Send me cake !

 

[johnnyb47]

Ohh yesss, That chain is way too long

 

[Jimmy Welch]

Technically 6 as you can't do odd on a chain. I win within 2 minutes of the original post. Send me cake !

You did mate , you are one of the few forces for good on the Internet