Crunch shortly after shifting

[Bodhbh]

Been a while...

I'm getting something between a ping and crunch from my drivetrain, it mostly occurs shortly after shifting, but it can pop up anytime, particularly if I'm putting down some gas after slacking off for a while. You can feel it through the pedals, it's almost like something is bedding in.

I've tinkered around with the indexing a bit, and also re-indexed from scratch, but it doesn't fix it. There's no play in the BB or cranks and the rear sprocket isn't loose. As always with these things, I can't reproduce the problem with the bike in the stand. I'm going to have a conserted tinker about this afternoon including checking the mech alignment - but assuming this doesn't fix it - any other thigns to check?

The last time I had a similar problem, it turned out to be a broken axle, however that also caused the freehub to play up (as it was filling up with metal fillings). Not getting that this time.

 

[Smokin Joe]

Knackered chain and/or cassette?

 

[Bodhbh]

Knackered chain and/or cassette?

I reckon they've done about 2k miles, although over winter - I'll stick it on the list to check the chain tho.

 

[faster]

Sounds like the freehub is slipping.

It starts off like this, just slipping one tooth, and will probably soldier on like that for ages before it becomes a problem.

 

[Erasmus]

I get this ocassionally, and have put it down to the freehub pawls being a bit sticky, staying down when freewheeling, and then not springing back up quick enough when pedalling again and 'catching'. This happened on some old wheels, and problem seemd to go away when I cleaned and regreased the pawl/spring gubbins etc. Have to get round to giving my current wheels a good service, but problem is too intermittent at the moment, and I'm too lazy....

Your description sounds similar to what I have experienced, particularly the bit about giving some effort after easing off, but good luck sorting out whatever it is, John

 

[Chislenko]

I would go for either cassette needs tightening a bit more or the sticking pawl as outlined above.

Have had personal experience of both so a process of elimination.

 

[Bodhbh]

Thanks for the advice. I've elimnated everything but the mech and the freehub, but most likely candidate is the freehub in retrospect - it's done about 60k miles without any service so I guess it's due one. I wish I'd asked a couple of days earlier or would've gone for it first.