broken sprocket teeth

[Ben Pfaff]

Recently my chain has started "skipping" when I start out hard.
I was assuming that it was just "chain stretch" until I looked at
the rear cluster. Almost half of the teeth were broken off on
the biggest sprocket! They were never like that before, and I'm
confused how it could have happened. What would cause a whole
bunch of teeth to break off a sprocket?

It's an old road bike--probably 1970s. The rear cluster is only
a 5-speed. I've only owned it for a year, so I don't know
whether the rear cluster is the same age as the rest of the bike.
I only ride the bike on the street, usually just to and from the
train station about a mile from my apartment.

Thanks,

Ben.
--
Ben Pfaff
email: [email protected]
web: http://benpfaff.org

 

[[email protected]]

Ben Pfaff wrote:
> Recently my chain has started "skipping" when I start out hard.
> I was assuming that it was just "chain stretch" until I looked at
> the rear cluster. Almost half of the teeth were broken off on
> the biggest sprocket! They were never like that before, and I'm
> confused how it could have happened. What would cause a whole
> bunch of teeth to break off a sprocket?
>
> It's an old road bike--probably 1970s. The rear cluster is only
> a 5-speed. I've only owned it for a year, so I don't know
> whether the rear cluster is the same age as the rest of the bike.
> I only ride the bike on the street, usually just to and from the
> train station about a mile from my apartment.
>
> Thanks,
>
> Ben.
> --
> Ben Pfaff
> email: [email protected]
> web: http://benpfaff.org

It happens. I had a 7 speed Suntour freewheel from the mid 1980s that
had a couple teeth broken off in the same area on one of the cogs.
Don't know how it happened. Did not notice it occurred until I
refurbished the bike in 1999. Thought about replacing the cog with the
missing teeth but my brother said it was not worth the effort. So I
just left it alone and test rode the bike to make sure it still worked.
It did.

My suggestion would be to not use the cog with the broken teeth. But
if you live in the Bay area, you may need the big cog. In which case,
go to a local bike shop and buy a real cheap 5 speed freewheel with a
big cog and have them put it on for $5. Or order a cheap freewheel
from Nashbar.

Shimano 5 speed freewheel for $14.95. 14-28 cogs. Probably the same
cogs you have now.
http://www.nashbar.com/profile.cfm?...and=&sku=15295&storetype=&estoreid=&pagename=

 

[Phil, Squid-in-Training]

> What would cause a whole
> bunch of teeth to break off a sprocket?

Your massive power overwhelming the puny strength of tiny cogs screaming out
for mercy! Be gentler, and sing to them every once in a while. Mozart
helps, too.

--
Phil, Squid-in-Training

 

[[email protected]]

Ben Pfaff wrote:
> Recently my chain has started "skipping" when I start out hard.
> I was assuming that it was just "chain stretch" until I looked at
> the rear cluster. Almost half of the teeth were broken off on
> the biggest sprocket! They were never like that before, and I'm
> confused how it could have happened. What would cause a whole
> bunch of teeth to break off a sprocket?
>
> It's an old road bike--probably 1970s. The rear cluster is only
> a 5-speed. I've only owned it for a year, so I don't know
> whether the rear cluster is the same age as the rest of the bike.
> I only ride the bike on the street, usually just to and from the
> train station about a mile from my apartment.
>
> Thanks,
>
> Ben.
> --
> Ben Pfaff
> email: [email protected]
> web: http://benpfaff.org

1970s 5-speed? The biggest cog on some (Shimano?) freewheels were
manufactured with every other tooth missing. Might you have one of
those?

 

[Ben Pfaff]

[email protected] writes:

> Ben Pfaff wrote:
>> [lots of broken teeth on biggest sprocket]
>> It's an old road bike--probably 1970s. The rear cluster is only
>> a 5-speed.
> 1970s 5-speed? The biggest cog on some (Shimano?) freewheels were
> manufactured with every other tooth missing. Might you have one of
> those?

Interesting suggestion--I didn't know that--but actually the
broken teeth are grouped together, not alternating, so I don't
think this is the case.
--
Ben Pfaff
email: [email protected]
web: http://benpfaff.org

 

[Jim Adney]

On Thu, 06 Oct 2005 12:50:21 -0700 Ben Pfaff <[email protected]>
wrote:

>Recently my chain has started "skipping" when I start out hard.
>I was assuming that it was just "chain stretch" until I looked at
>the rear cluster. Almost half of the teeth were broken off on
>the biggest sprocket! They were never like that before, and I'm
>confused how it could have happened. What would cause a whole
>bunch of teeth to break off a sprocket?

I think it's most likely that they have always been that way and that
you just never noticed it before. Some makers did skip tooth sprockets
on the largest cogs in that era.

Look it over carefully. Are the missing teeth in a pattern, like every
other tooth, or 2 out of every 3, missing?

I'll bet that your first assumption is probably the right one: Your
chain is worn out.

-
-----------------------------------------------
Jim Adney [email protected]
Madison, WI 53711 USA
-----------------------------------------------

 

[Booker C. Bense]

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In article <[email protected]>,
Ben Pfaff <[email protected]> wrote:
>Recently my chain has started "skipping" when I start out hard.
>I was assuming that it was just "chain stretch" until I looked at
>the rear cluster. Almost half of the teeth were broken off on
>the biggest sprocket! They were never like that before, and I'm
>confused how it could have happened. What would cause a whole
>bunch of teeth to break off a sprocket?
>
>It's an old road bike--probably 1970s. The rear cluster is only
>a 5-speed. I've only owned it for a year, so I don't know
>whether the rear cluster is the same age as the rest of the bike.
>I only ride the bike on the street, usually just to and from the
>train station about a mile from my apartment.
>

_ It happens. In particular, I remember a period in the late 80's
when I would strip the teeth off a freewheel cog about every couple
months on my MTB. When the first hyperglide freewheels came out
the problem fixed itself. Freewheels are dirt cheap these days.
Get a new one.

_ Booker C. Bense

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[Robin Hubert]

[email protected] wrote:
> Ben Pfaff wrote:
>
>>Recently my chain has started "skipping" when I start out hard.
>>I was assuming that it was just "chain stretch" until I looked at
>>the rear cluster. Almost half of the teeth were broken off on
>>the biggest sprocket! They were never like that before, and I'm
>>confused how it could have happened. What would cause a whole
>>bunch of teeth to break off a sprocket?
>>
>>It's an old road bike--probably 1970s. The rear cluster is only
>>a 5-speed. I've only owned it for a year, so I don't know
>>whether the rear cluster is the same age as the rest of the bike.
>>I only ride the bike on the street, usually just to and from the
>>train station about a mile from my apartment.
>>
>>Thanks,
>>
>>Ben.
>>--
>>Ben Pfaff
>>email: [email protected]
>>web: http://benpfaff.org
>
>
> It happens. I had a 7 speed Suntour freewheel from the mid 1980s that
> had a couple teeth broken off in the same area on one of the cogs.
> Don't know how it happened. Did not notice it occurred until I
> refurbished the bike in 1999. Thought about replacing the cog with the
> missing teeth but my brother said it was not worth the effort. So I
> just left it alone and test rode the bike to make sure it still worked.
> It did.
>
> My suggestion would be to not use the cog with the broken teeth. But
> if you live in the Bay area, you may need the big cog. In which case,
> go to a local bike shop and buy a real cheap 5 speed freewheel with a
> big cog and have them put it on for $5. Or order a cheap freewheel
> from Nashbar.
>
> Shimano 5 speed freewheel for $14.95. 14-28 cogs. Probably the same
> cogs you have now.
> http://www.nashbar.com/profile.cfm?...and=&sku=15295&storetype=&estoreid=&pagename=
>

I used to break teeth off 7sp DA freewheel cogs.


Robin Hubert