How to fix bent cassette teeth?

I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

laters,

marz

Marz wrote:
I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

laters,

marz

No real way to fix but there are many casette 'levels', and the less
expensive ones are not necessarily going to wear faster..mostly just
less 'pretty' and 'heavier'...least expensive cogset and chain is a
good way to go...these are consumables afterall...

On 14 Sep 2006 05:26:00 -0700, Marz wrote:

How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

I would try heavy pliers, but chances are that in getting the tips of the
teeth back into line, you're going to distort the cog to the point where
it'll interfere with the chain on the next one. It's hard to see how
you could support the cog while pushing its teeth straight, unless you
had steel spacers you could wedge between each cog from that one
to the largest.

--
Home page: http://members.westnet.com.au/mvw

Marz wrote:

How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

I bent a cog last fall and rode the bike through most of the winter,
re-bending it as required. When it happened on the trail I would just
grab a rock and bash it straight. Occasionally at home I used a nail
punch and hammer.

That lasted for a month or two of riding until my primitive metal
working techniques finally snapped off the teeth. Fortunately, it was
an the largest cog so I just didn't use it for the rest of the winter.

Now that I think about it, since I was riding on snow, I wasn't able to
put a lot of load on that cog. Riding under normal conditions, it might
not have held up at all under that treatment.

Regards,
Anthony

Marz wrote:
I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

laters,

marz

It's not clear if you've checked this, but many cassettes are easy to
disassemble completely because they're held together by long, skinny
bolts. Many more have rivets which can have their heads ground off to
take apart the cassette. The rivets are for convenience and
structurally unimportant; it'll work just as well if all the cogs are
loose on the freehub body. If you can get your cassette apart in this
way, it would probably be much easier to try straightening the teeth. I
haven't done this, but I might try clamping the cog with bent teeth in
a vise with smooth jaws so that one bent tooth at a time was poking up
above the jaws, and bend them with pliers. (Most or all spidered
cassettes wouldn't let you do this very easily because the cogs are
riveted onto the spider).

It's important that the cog not get bent into a slight potato-chip
shape, so I would be careful with your approach.

Michael Warner wrote:

On 14 Sep 2006 05:26:00 -0700, Marz wrote:

How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

I would try heavy pliers, but chances are that in getting the tips of the
teeth back into line, you're going to distort the cog to the point where
it'll interfere with the chain on the next one. It's hard to see how
you could support the cog while pushing its teeth straight, unless you
had steel spacers you could wedge between each cog from that one
to the largest.

I'd try a hefty screwdriver inserted down to the carrier, wedging the
bent portion back in the direction it belongs. This will place the
force on the same area that was used to bend the cog initially, so
might result in a fairly good fix. The good news is that it doesn't
matter if the "inside" bits of the cog are straight - just get the
teeth reasonably in line and you should be good to go.

I've also fixed bent cogs on cassettes with reomoveable cogs - just
laid 'em on the garage floor and pounded 'em straight with a hammer.
Never had a problem with one after repair.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

On 14 Sep 2006 05:26:00 -0700, "Marz" wrote:

I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

Virtually all cassettes can be disassembled if you're persistent
enough and equipped with the proper tools. A Dremel can be invaluable
for this; grind off the heads of the rivets on the back side, and the
thing can usually be pried apart. Once you have the bent sprocket in
hand, lay it on a suitalbe durface (an anvil is best) and gently tap
the teeth back flat with a hammer. Don't whach them too hard or
you'll flatten them out, making them wider and thinner in the process;
a Bad Thing. You just want to bend them back close to where they
started.

Alternate approach, assuming the teeth are bento toward the smaller
sprockets: Use a big pair of slip-joint pliers ("water pump pliers",
like http://tinyurl.com/pwkqx) with the lower jaw behind the big
sprocket and the upper one reaching in to the tooth to push it back
over.

Other methods can be devised depending on the tools at hand. These
are just the two that occurred to me off the top of my head.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack wrote:
On 14 Sep 2006 05:26:00 -0700, "Marz" wrote:

I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

Virtually all cassettes can be disassembled if you're persistent
enough and equipped with the proper tools.

Are you including cassettes with the cogs riveted onto their
spiders/carriers in this? Any tips on getting the cogs attached again?

Werehatrack wrote:
On 14 Sep 2006 05:26:00 -0700, "Marz" wrote:

I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

Virtually all cassettes can be disassembled if you're persistent
enough and equipped with the proper tools. A Dremel can be invaluable
for this; grind off the heads of the rivets on the back side, and the
thing can usually be pried apart. Once you have the bent sprocket in
hand, lay it on a suitalbe durface (an anvil is best) and gently tap
the teeth back flat with a hammer. Don't whach them too hard or
you'll flatten them out, making them wider and thinner in the process;
a Bad Thing. You just want to bend them back close to where they
started.

Alternate approach, assuming the teeth are bento toward the smaller
sprockets: Use a big pair of slip-joint pliers ("water pump pliers",
like http://tinyurl.com/pwkqx) with the lower jaw behind the big
sprocket and the upper one reaching in to the tooth to push it back
over.

Other methods can be devised depending on the tools at hand. These
are just the two that occurred to me off the top of my head.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Cheers for all the advice. It's a sram cassette with a spider and
rivots and it's not possible to disassemble. In the end I removed the
cassette from the wheel, placed it flat on the floor and applied 222
pounds of fat gut through a large screw driver to each tooth that was
bent out. Couldn't get it perfect, but good enough that the chain
didn't skip.

I've not seen a cassette that's made to disassemble in years. Does
anyone else recall the cassettes that were held together with three
long bolts. You could strip them down, cleaning each small spocket and
even build your own custom combination of spockets. Both Shimano and
Sram seem to favour rivoted spiders.

Laters,

Marz

Marz wrote:
Werehatrack wrote:
On 14 Sep 2006 05:26:00 -0700, "Marz" wrote:

I don't know how it happened, honestly, I was just riding along. Well,
ok hammering a sweet section of trail, but there was no crash or clang.
I finished the section of trail, shifted up to an easier gear to start
the next climb and my chain begins to leap of the cassette. I thought
great, I've got something caught in the teeth or in the rear mech, but
no, on closer examination I've managed to bend about 5 teeth, on the
4th gear, out by about 2-3mm. Not alot, but enough so the chain won't
sit in that gear and it get's pushed off the next gear and so I'm out 2
gears.
How do I fix that? There's not enough room to bend it back into shape
and it's not a cassette I can disassemble. So I'm left with the gentle
tap-tap of a pin hammer, not easy, replacing the cassette, expensive,
or hopefully someone has a solution.

Virtually all cassettes can be disassembled if you're persistent
enough and equipped with the proper tools. A Dremel can be invaluable
for this; grind off the heads of the rivets on the back side, and the
thing can usually be pried apart. Once you have the bent sprocket in
hand, lay it on a suitalbe durface (an anvil is best) and gently tap
the teeth back flat with a hammer. Don't whach them too hard or
you'll flatten them out, making them wider and thinner in the process;
a Bad Thing. You just want to bend them back close to where they
started.

Alternate approach, assuming the teeth are bento toward the smaller
sprockets: Use a big pair of slip-joint pliers ("water pump pliers",
like http://tinyurl.com/pwkqx) with the lower jaw behind the big
sprocket and the upper one reaching in to the tooth to push it back
over.

Other methods can be devised depending on the tools at hand. These
are just the two that occurred to me off the top of my head.

Cheers for all the advice. It's a sram cassette with a spider and
rivots and it's not possible to disassemble. In the end I removed the
cassette from the wheel, placed it flat on the floor and applied 222
pounds of fat gut through a large screw driver to each tooth that was
bent out. Couldn't get it perfect, but good enough that the chain
didn't skip.

I've not seen a cassette that's made to disassemble in years. Does
anyone else recall the cassettes that were held together with three
long bolts. You could strip them down, cleaning each small spocket and
even build your own custom combination of spockets. Both Shimano and
Sram seem to favour rivoted spiders.

Only higher end cassettes are spidered. There are still a good number
of options for ones that aren't.