Transmission slipping

[Tim Hall]

The Boy's Hardrock is suffering, and has been for a while, from a slipping transmission.

Initially (about a year ago I think) I thought it was a worn chain so I changed it. It was worn (12 1/8 inches IIRC), so I changed the cassette as well. Slight improvement, but not a full cure.  New chain was Sram 8 speed vanilla, cassette Sram 8 speed.

It's got much worse lately,skipping when extreme welly is applied to the pedals.  I had a more detailed look at it today, bearing in mind he's done not more than a thousand miles on it since I fitted the new components.

The chain, as measured by my very faded steel rule is only a smidgeon over 12 inches for 12 links. The cassette doen't seem particularly worn. 

Earlier in the week I fitted a new large charge ring (he'd bent the previous one somehow). It skips on this, as well as the others.

Is it possible that the freehub is skipping under load?  If so, I guess the simplest fix is to fit a new one.

Any other ideas welcome.

[Torslanda]

Got a spare rear wheel? Transfer the cassette and try it under load. If it doesn't skip you've got a dodgy hub. Checked the chain for stiff links?

J

[gordon taylor]

Check the chain for stiff links - as the man says.

That's what always seems to cause dodgy gears in the Gordy fleet.

[Biggsy]

I have not experienced or heard of a freehub failing in a way that results in the same sound and feeling of a chain skipping on a sprocket/chainring.

[Zoidburg]

I have seen cassettes skip because of the pawls in the freehub body not engaging

It is common with original equipment shimano clones on lower end bikes

[Biggsy]

I have ridden a faulty freehub that was intermittently engaging and not engaging, but it felt and sounded different from a chain skipping on a sprocket. 

[Polar Bear]

Loose cassette?  Bent hanger? Rear mech alignment?

[Tim Hall]

Thanks everyone for your input so far.

Addressing various points:

I don't have a spare 8 speed wheel. I've got a 7 speed and will have a go with that.

(Can I fit an 8 speed cassette onto a 7 speed free hub? I vaguely recall they have different spine patterns.)

No stiff links as far as I can see.

The slipping is intermittent, which is what pointed me towards the free hub, althouggh I take Biggsy's point about the different sound and feel.

Cassette is done up tight. I took it off and cleaned it all last night.
Hanger has been replaced a few months back. I'll check mech alignment once my fingers thaw out.

[MSeries]

(Can I fit an 8 speed cassette onto a 7 speed free hub? I vaguely recall they have different spine patterns.)

Assuming Shimano (style) freehub body.  7 Speed came/come in both Uniglide and Hyperglide (HG) if yours is a HG then the 8 speed will slide on, not sure if you'll be able to get the lockring on though. Lockring ? If your 7 speed has a lockring and not a threaded end sprocket then it's  HG.