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PostPosted: Sun Mar 17, 2013 6:01 pm 
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I vote for chain being too long as the cause.


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PostPosted: Sun Mar 17, 2013 9:32 pm 
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Do you mean the chain is actually jumping, or the cranks are 'slipping'. Is it a harsh, violent motion, or just annoying?


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PostPosted: Sun Mar 17, 2013 10:11 pm 
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Can you post a picture with the chain cross-geared, small chainring to smallest cog?

With the chain on the smallest cog at the back, do both pulley wheels and the smallest cog line up vertically?

Is there any slack in your rear shift cable when the chain is on the smallest cog?


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PostPosted: Sun Mar 17, 2013 11:34 pm 
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jimo746 wrote:
have a play about with the cassette/freehub, move it back and then forwards, it should engage within a very small distance (not sure on the specifics, probably out there if you Google though), I once had a freehub that turned about a quarter of a revolution before it would engage (obviously the pawls inside it were knackered) , it's more likely to slip under load though, so annoyingly a workbench test doesn't always show the problem up.

And I have seen cassettes spin on the freehub body before, had a freehub body that had been mangled by the cassette wearing down and gouging the locking splines on the freehub itself, under load it was enough to let the entire cassette move around on the freehub body.


To be honest, testing it, things work fine, ie. with bike on a clamp or upside down, but testing means I haven't the same resistance as riding.


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PostPosted: Sun Mar 17, 2013 11:35 pm 
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dav101 wrote:
seeing as its got a new chain, cassette and cranks, it definitely sounds like the freehub imo
replacement springs and pawls are in order i'd say, if you're wanting to keep the hub, if not you can usually pick up wheels/hubs on here pretty cheap

EDIT: what hub is it?


The Hub is LX, which I bought from a seller here (on Mavic 221)


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PostPosted: Sun Mar 17, 2013 11:37 pm 
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New chain and worn cassette?


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PostPosted: Mon Mar 18, 2013 12:01 am 
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I had a similar issue not so long ago and tried everything, it turned out the hanger was bent by a couple of mm. Too little to see with the naked eye. Not something I've had before and it was actually a mechanic at the LBS that worked it out as I eventually cracked and got them to look at it.


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PostPosted: Mon Mar 18, 2013 12:13 am 
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mechagouki wrote:
Can you post a picture with the chain cross-geared, small chainring to smallest cog?

With the chain on the smallest cog at the back, do both pulley wheels and the smallest cog line up vertically?

Is there any slack in your rear shift cable when the chain is on the smallest cog?



I will do that asap (probably tomorrow)


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PostPosted: Mon Mar 18, 2013 12:37 am 
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The hub is LX M563 on Mavic 221 rims.
I bought the wheels from trek_y back in November last year (2012)

This is the sale thread;
viewtopic.php?f=2&t=231596
This is how the wheels have been described;
Wheels - Deore LX M563 black hubs, Mavic 221UB rims, DT spokes - hubs nice and smooth, no dings or wobbles, come with Shimano classic chrome skewers. £55. Or £65 with Specialised Nimbus 1.5 semi slicks, tubes and 8 speed cassette as shown.

All I did was change the cassette to a 9 speed one and put new set of Continental's on.

The guy at the LBS who fit the gears up for my boy ( a few months back) said the long cage rear mech will have problems - that a med cage would be better.
I wonder if that's the problem?

The cassette is a brand new HG unit from CRC.

What happens is that riding at a leisurely pace, nothing, as soon as i put some welly in it - I can pedal, after say every other revolution (sometimes every rev, sometimes nothing for 3 revs - intermittent) what happens is that on the downward push of the pedal something at the rear will slip and the pedalling motion will be distracted as it seems something has 'given' and the crank (and thus my foot on the pedal) will slip down a short way from say (imagining the pedal revolution is a circle ((which it is)) 60' to 120' degrees.

And on the middle chain ring, this was happening when geared on the smaller cogs.

When I slackened the chain some more by changing gears- on the smallest chain ring, pedalling was fine.

I need to check;

a) the chain line and BB spindle length (what size Bottom Bracket would be for these cranks which are fitted?)
b) chain size - too many links?


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PostPosted: Mon Mar 18, 2013 12:49 am 
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ibbz wrote:
dav101 wrote:
seeing as its got a new chain, cassette and cranks, it definitely sounds like the freehub imo
replacement springs and pawls are in order i'd say, if you're wanting to keep the hub, if not you can usually pick up wheels/hubs on here pretty cheap

EDIT: what hub is it?


The Hub is LX, which I bought from a seller here (on Mavic 221)



shimano are notorious for the free hubs going, if i remember rightly they only use a 2 pawl system
my xt recently started letting go too.


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