Cassette won't engage back wheel - what is wrong?

[Graham]

I cycled over a tarmac ramp as I arrived at work, as I do every day.
But the bump dislodged the chain, and when I got the chain back into
place, the cassette was running freely and would not engage the back
wheel - so now I can only free-wheel my bike.

I'm sure it means a trip to lbs, but does anybody know what went
wrong? Do I need a new cassette, or has something come loose?

Graham
--
Graham Steel: [email protected]
Web: http://www.steelworks.org.uk

 

[davek]

Graham wrote:
> Do I need a new cassette, or has something come loose?

If it were an old-fashioned screw-on freewheel, you could replace that.
But replacing the cassette won't help if it's a freehub. Completely wild
guess: you've dislodged a spring in the hub when going over the bump.

If that's what it is, I believe it /is/ possible to fix, though it's not
something I would attempt myself.

d.

 

[Nigel Cliffe]

Graham wrote:
> I cycled over a tarmac ramp as I arrived at work, as I do every day.
> But the bump dislodged the chain, and when I got the chain back into
> place, the cassette was running freely and would not engage the back
> wheel - so now I can only free-wheel my bike.
>
> I'm sure it means a trip to lbs, but does anybody know what went
> wrong? Do I need a new cassette, or has something come loose?

Freewheeling both forwards and backwards ? Probably the pawls which cause
the "click click click" freewheel noise are stuck in the "up" position. Bit
of WD-40 in the right place will probably free them, then a bit of light
oil.
Check Sheldon Brown on how free wheels work on both screw-on hubs and modern
cassettes. If you can work out which your bike has, chances are you can work
out where to spray the WD-40. Shouldn't need to dismantle anything beyond
removing wheel from bike, lay horizontally, spray in the right place and
work the cogs back and forth, the free-wheel should unstick itself.

Sheldon is at: www.sheldonbrown.com

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

 

[John Miller]

"Graham" <[email protected]> wrote in message
news:[email protected]...
>I cycled over a tarmac ramp as I arrived at work, as I do every day.
> But the bump dislodged the chain, and when I got the chain back into
> place, the cassette was running freely and would not engage the back
> wheel - so now I can only free-wheel my bike.
>
> I'm sure it means a trip to lbs, but does anybody know what went
> wrong? Do I need a new cassette, or has something come loose?
>
> Graham
> --
> Graham Steel: [email protected]
> Web: http://www.steelworks.org.uk

Graham

If it is a cassette (and not a freewheel), then replacing it won't do any
good as the problem lies within the freehub which is part of the axle. They
can be fixed or replaced, but you'll need at least one special tool,
depending upon the make (Shimano, Campagnolo?) You can get an idea of what's
involved if you look at the Park Tool website
www.parktool.com/repair/byregion.asp?catid=4&imageField2.x=6&imageField2.y=6

John Miller

 

[Chris Eilbeck]

[email protected] (Graham) writes:

> I cycled over a tarmac ramp as I arrived at work, as I do every day.
> But the bump dislodged the chain, and when I got the chain back into
> place, the cassette was running freely and would not engage the back
> wheel - so now I can only free-wheel my bike.
>
> I'm sure it means a trip to lbs, but does anybody know what went
> wrong? Do I need a new cassette, or has something come loose?

Have you tried percussive maintenance?

Chris
--
Chris Eilbeck

 

[Graham]

Thanks for all the replies. What I learned is: I don't have a
cassette, I have a freewheel. I did not realise that there were two
different types of mechanism. I now have a new freewheel and the bike
is on the road again.

Graham


On Tue, 23 May 2006 21:16:05 GMT, [email protected]
(Graham) wrote:

>I cycled over a tarmac ramp as I arrived at work, as I do every day.
>But the bump dislodged the chain, and when I got the chain back into
>place, the cassette was running freely and would not engage the back
>wheel - so now I can only free-wheel my bike.
>
>I'm sure it means a trip to lbs, but does anybody know what went
>wrong? Do I need a new cassette, or has something come loose?

--
Graham Steel: [email protected]
Web: http://www.steelworks.org.uk