Rear cog set slipping.

WilburHonk said:

Hi,
Hope someone can help.
I've been having problems for quite some time now with what I thought
was my rear derailer jumping, but tonight I found out that it wsan't my
derailer, it was actually the entire rear cog set that wasn't biting
properly and was just spinning as I pedalled.
Does anyone out there know what I need to do to get it fixed? Do I just
get a new set or do I need to get a new wheel as well?

It's either a freewheel, or a freehub. (See
<http://www.sheldonbrown.com/freewheels.html> for descriptions).

If it's a freewheel, the pawls (weeny spring loaded teeth) that give
it it's freewheel action can get gummed up with crud. A possible fix
is to squirt with WD40 or rinse it in white spirit, to remove the
crud. The pawls are then free to move and engage in the outer edge of
the freewheel and transmit the drive. Alternatively a new freewheel
isn't that expensive (15 quid or so from wiggle, depending on spec).
If it's been on the bike for a long time be prepared for a bit of a
struggle in getting it off. You'll need a freewheel removal tool as
well, a few quid more.

I've not heard of a freehub having this problem, but don't see a
logical reason why it shouldn't. Again try the WD40 trick first.
Sheldon has an article on how to remove the freehub body - again
you'll need a special tool, plus a chain whip.

In either case I'd try the WD40 first and if that doesn't work ask
your LBS to replace it if you're not sure of what to do.

Tim

WilburHonk said:

Hi,
Hope someone can help.
I've been having problems for quite some time now with what I thought
was my rear derailer jumping, but tonight I found out that it wsan't my
derailer, it was actually the entire rear cog set that wasn't biting
properly and was just spinning as I pedalled.
Does anyone out there know what I need to do to get it fixed? Do I just
get a new set or do I need to get a new wheel as well?
To be honest, I think it's time that it got a few quid spent on it
anyway so I don't mind harsh realities!
Thanks

This can be fixed without replacing the wheel.

Depending on the age of the bike, it uses one of two systems back
there.
"Freewheel": the cogs and the ratcheting system that allow the bike to
freewheel are one item which is pretty much unopenable.
"Freehub": the cogs (aka "casette"😉 can be removed from the
freewheeling bit ("freehub body"😉, and either can be replaced
seperately.

A better description of all of this, including diagrams and information
on how to tackle this yourself and the tools required is at:
http://www.sheldonbrown.com/freewheels.html

Either way, it requires at least one specialist tool to remove the
freewheel from the wheel hub, or the cogs from the freehub body. Unless
you already have these tools to hand, a visit to the local bike shop is
probably in order.
A freewheel in particular also requires considerable strength and a
large bench vise or honking great wrench to remove, especially if it's
been on there a while. The freehub is physically easier to get off.

It is sometimes possible to bring a failing freewheel or freehub back
to life by removing it, flushing it out with solvent or cleaner, and
re-oiling it. However, this only works if the problem is due to it
being clagged up rather than mechanically broken. If you're not able
to remove the old one yourself, I'd suggest that it might be more
ecconomic to get a new one now, rather than pay a second set of labour
in a few weeks if/when it start failing again. IME, once they start
going, there's not a great deal of life left in them.

A new freewheel will set you back 10-20 quid, plus a fiver or so to
fit. It's easiest if you get one with the same number of cogs as the
existing one.
A new freehub will set you back about the same, possibly a little more
for fitting since there's one or two more steps.

To buy the tools will probably cost you about as much as the labour, so
the LBS may make more sense if this is a one off.

It's good practice to replace the chain if replacing the cogs - it's
probably due anyway if it's about the same age as a failing
freewheel/freehub, and should cost about 10 quid, and no more that a
couple of quid labour to fit. Sheldon's site (as above) also has lots
of info on how to check for wear in the cogs, chain, and front
chainrings. Best to replace any of these items showing significant
wear as a set.

Hope this helps,

bookieb.

bookieb said:

Depending on the age of the bike, it uses one of two systems back
there.
"Freewheel": the cogs and the ratcheting system that allow the bike to
freewheel are one item which is pretty much unopenable.
"Freehub": the cogs (aka "casette"😉 can be removed from the
freewheeling bit ("freehub body"😉, and either can be replaced
seperately.

A better description of all of this, including diagrams and information
on how to tackle this yourself and the tools required is at:
http://www.sheldonbrown.com/freewheels.html

More specifically, I have a page just devoted to how to tell the
difference betwixt the twain:

http://sheldonbrown.com/free-k7

Sheldon "Over 2,000 Pages" Brown
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
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Tim Hall said:

I've not heard of a freehub having this problem, but don't see a
logical reason why it shouldn't.

Certainly not unknown - Dad had a Miche cassette hub on his bike that
gave up in this way. I've also experienced the problem, but that was
with a Shimano screw-on block where the ratchet gave up the ghost,
leaving me in "permanent freewheeling" mode!

David Belcher