Chain jumping - changed everything!

[yenrod]

For what it's worth I had a similar problem a few years ago, I changed the cassette and chain but that had no effect. I took it to the LBS and they diagnosed a bent derailleur, they replaced it and that cured it.

When you MAG talked of the deraileur hanger being bent in 'AS IT SHOULD BE' - this should NOT be the case as it hanger should be VERTICAL no in or out just straight down in any direction.

Sometime though MAG when screwing on a deraileur you'll have the threads on the frame warped so as the deraileur screws on the actual vertical 'hang' of the deraileur will not be totally straight down and will point in or out or bend sideways slightly or inward...

Or even the Bolt (thats in the deraileur) that screws in to the deraileur frame dropout, is bent = new bolt OR deraileur...

It could be this - check this ?

 

[andygates]

It should definitely be straight as a straight thing.

If you've changed cassette, you might also want to adjust the B-tension screw (it's the one that isn't the limit screws). This controls how closely the derailleur tracks the block.

 

[theoriginaldus]

Ok, well I've has another look at the chainset and its defintely not warn enough to warrant replacement - compared to the other cogs, the outside ring which is the only one I really use looks identical.

Reading up on it a bit more I'm pretty sure it's also not because I need a short cage derailleur - this doesn't seem to me to have the capacity to generate this kind of fault. Also I still have a triple chainset so I'm reluctant to change to the short cage in case the day comes when I shift to the inner chainset ring forgetting I have it

I am more and more going towards this being a freehub problem tbh although it is a little odd that it wasn't apparent before I changed the chain, derailleur and cassette. However...when changing the cassette originally I did not use a chain whip, so tightening up the lockring I was doing it against the ratchet of the freehub, do you think this could have caused a problem? Also, is there any way of testing whether the freehub ratchet is slipping? Could I just give it a good pull with a chain whip? Not sure I could recreate the same pressure tho tbh.....

When talking about a bent derailleur, how much are we talking about it being bent before it causes an issue, particularly outwards. Mine is very slightly pointing outwards from the wheel, were talking a couple of degrees max though.

Andy, I did adjust the b tension screw to get the best contact I could between derailleur and cassette

Fossyant, its a new SRAM chain. The old chain had warn the cassette hence changing the derailleur and chain required a new cassette also.

Yenrod, when I say about bending it how it should be, my frame doesn't use a hanger, the derailleur just screws straight into the frame. The actual frame here was bent so the derailleur was pointing inwards towards the wheel, I had to bend it out again so the derailleur was as straight as possible without the chain catching on the frame when on the outer ring. This meant it had to very slightly point outwards, max couple degrees as above. When overhauling the hub I didn't actually take all the nuts off the axle and roll it on a flat surface, partly because they were on bloody tight and partly because I didn't want to lose placing and have to fiddle about getting the axle position right again However with close inspection it looked as straight as many people would consider to be straight.

1 vote for rear freehub needs replacing, any advances?

 

[Steve Austin]

Have you got a different wheel to try?
if the freehub has gone the cassette (when attached) will rock slightly from side to side

 

[theoriginaldus]

Hi Steve, unfortunately I don't have a spare wheel to swap out, bah! However I will test for a rocking movement on the cassette. I don't recall noticing any rocking when changing the cassette or overhauling the hub, but then I wasnt looking for it. How much movement are we talking about here? Should there be absolutely no movement at all if its ok and any rocking even slight is not good or does it have to be a good few degrees to be dodgy?

Man this is really hard to pin down to definitely being one component. Or maybe (probably) I'm just rubbish
​

 

[andygates]

Easy to pin down to the freehub: ride along watching it. Just don't hit things.

 

[theoriginaldus]

Ok thanks Andy, I'll try giving that a crack and hope I don't stack it into a wall or something

 

[theoriginaldus]

I have now noticed that there is definite side to side movement on the back wheel. Its not much but it is there. I'm guessing this is not correct and means that the cassette is moving with the wheel? This could be causing the chain to go out of line with the cassette a little and with the extra pressure applied when standing to peddle could just be making it jump off the ring a little do you think? What do I need to do to correct this? A spacer as bianco has suggested?