Chain slip/jam - Rear Derailleur?

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dhd.evans

Veteran
Location
Dundee
I completed a sportive on Sunday with some slightly odd chain slippage, nothing drastic or life-changing but enough that pricked my ears. I dropped a few cogs on the back going uphill and the chain sounded like it slipped right over the jockey wheels and then clamped back into place. And odd free-wheeling sensation but i managed to complete without further issue.

Anyway, moving onto this week I came out of a junction last night with the slipping sensation, vowed to clean the bike up last night at the same moment that the chain completely locked up on me and i went arse over tit. The remainder of the ride i was careful on the gears and noticed a little lag when clicking through - maybe cable tension? Not sure.

So, cleaned the bike up, ran the chain across the gears and lubed it good (hurr hurr). I then tightened the cable with the barrel adjuster at the front but no work on the back.

Same lag, same slipping sensation and a minor lock-up when trying to rifle through the cassette before hitting a hill.

Can someone diagnose for me?
 

Cycleops

Legendary Member
Location
Accra, Ghana
Do you know how the chain locked? What position was it in when you looked?
 
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dhd.evans

dhd.evans

Veteran
Location
Dundee
Not sure how it locked, possibly the rear mech was completely stretched out. It just jammed wholesale and i went down.
 

Shut Up Legs

Down Under Member
@dhd.evans : I had a similar problem, and it turned out that the freehub body was faulty. Unfortunately, the ones I use aren't really serviceable, so they either work or they don't and you have to replace them. Because the freehub body was sticking (i.e. the rachet / pawl arrangement wasn't working), the chain started sticking whenever I stopped pedaling.
 
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dhd.evans

dhd.evans

Veteran
Location
Dundee
Hmmm, that's a decent shout. Freehub is in Fulcrum Racing 7 wheels but have only put maybe 1000mi through it? Would it wear that bad that quick?
 

raleighnut

Legendary Member
Bent gear hanger ?
 
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dhd.evans

dhd.evans

Veteran
Location
Dundee
Going to investigate cable tension, hanger and cassette position over lunchtime before my ride home.

I'll look at the freehub over the weekend, hopefully nothing as serious - it's not rough, bearings seem OK at the moment (have had to replace the freehub on other wheels in a previous life) and no obvious clicking.

Will report back!
 

Rooster1

I was right about that saddle
Possible causes.
- Chain has one or more stiff links which can create jumping between back rings
- Chain and cassette are spent
- Cassette has some play (freebub movement)
- Rear Derailleur needs adjusting
 
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dhd.evans

dhd.evans

Veteran
Location
Dundee
Possible causes.
- Chain has one or more stiff links which can create jumping between back rings
- Chain and cassette are spent
- Cassette has some play (freebub movement)
- Rear Derailleur needs adjusting

I hadn't considered the first one there - chain is less than 200mi old, cassette 300mi-ish but there coudl be a stiff link. I did run it through the cyclone cleaner and applied wet dry lube afterwards. Will add this to the list of investigations.

1. Cable tension
2. Hanger
3. Chain links
4. Cassette wobble
5. Freehub

Cheers all, think i've got a plan of action now.
 
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