Why does chain seem to skip one cog when I start pedaling?



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Pat

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Hello. I have a problem with my mountainbike that's been pretty common with bikes I've had but now
find it really irritating and want to fix it.

When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal jerkily
advances a little bit without the wheels moving and then it "catches" and the wheels turn as the
pedal turns. It almost feels like every link on the chain is skipping one cog but that seems
impossible for every cog would have to be worn.

When it happens, it's a jolt to the body which once in a while almost knocks me off the bike.

The bike is not knew so I think it's due to worn parts but I can't figure out what exact parts are
causing it. Any help would be appreciated.

Thanks.
 
G

GearóId Ó Laoi

Guest
Get someone to look carefully at the bike when you're doing it and you will spot where the movement
is, if not in your imagination.
 
R

Richard Ney

Guest
Pat writes:

> Hello. I have a problem with my mountainbike that's been pretty common with bikes I've had but now
> find it really irritating and want to fix it.
>
> When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal
> jerkily advances a little bit without the wheels moving and then it "catches" and the wheels turn
> as the pedal turns. It almost feels like every link on the chain is skipping one cog but that
> seems impossible for every cog would have to be worn.
>
> When it happens, it's a jolt to the body which once in a while almost knocks me off the bike.
>
> The bike is not knew so I think it's due to worn parts but I can't figure out what exact parts are
> causing it. Any help would be appreciated.

You may want to have a look at the FAQ: http://draco.acs.uci.edu/rbfaq/FAQ/8d.2.html
 
T

Trent Piepho

Guest
In article <[email protected]>, Pat <[email protected]> wrote:
>Hello. I have a problem with my mountainbike that's been pretty common with bikes I've had but now
>find it really irritating and want to fix it.
>
>When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal jerkily
>advances a little bit without the wheels moving and then it "catches" and the wheels turn as the
>pedal turns. It almost feels like every link on the chain is skipping one cog but that seems
>impossible for every cog would have to be worn.

That's exactly what's happening, it's called chain skip.

>The bike is not knew so I think it's due to worn parts but I can't figure out what exact parts are
>causing it. Any help would be appreciated.

It could be caused by a stiff link in the chain. Try running the chain backward while watching where
the chains loops about though the derailleur. One of the links might not bend all the way. If you
find one, try bending the chain side to side (ie. not the way the chain is supposed to bend) with
your hands at the link, to loosen the joint up.

You can also try to find what is worn by checking what gears it happens in. If it only happens in a
certain chainring or sprocket, then that's the one that needs to be replaced.

Most likely, it is the chain that is worn, and you'll get the most skip in the smallest gears. You
can measure your chain with a ruler. Measure the distance between 12 links. It should be 12 inches,
but you're chain will be a bit longer from wear. If it's more than than 1/8 inch longer than a foot,
the chain is worn out. If your chain is really worn, then your rear sprockets are probably worn out
too. When you replace the chain, the new chain on the old sprockets will skip even worse than the
old chain did, so you'll have to replace them too.
 
P

Paul Kopit

Guest
On Sat, 3 May 2003 21:39:20 -0700, "Pat" <[email protected]> wrote:

>When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal jerkily
>advances a little bit without the wheels moving and then it "catches" and the wheels turn as the
>pedal turns. It almost feels like every link on the chain is skipping one cog but that seems
>impossible for every cog would have to be worn.
>
>When it happens, it's a jolt to the body which once in a while almost knocks me off the bike.

Sounds like something that happened to me. I kept looking at the rear derailleur adjustments and the
cassette and it was the middle ring on a triple crankset. If you rotate the offensive ring, it will
not skip when you start out. You still need a new ring.
 
J

John Thompson

Guest
In article <[email protected]>, Pat wrote:

> Hello. I have a problem with my mountainbike that's been pretty common with bikes I've had but now
> find it really irritating and want to fix it.
>
> When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal
> jerkily advances a little bit without the wheels moving and then it "catches" and the wheels turn
> as the pedal turns. It almost feels like every link on the chain is skipping one cog but that
> seems impossible for every cog would have to be worn.
>
> When it happens, it's a jolt to the body which once in a while almost knocks me off the bike.
>
> The bike is not knew so I think it's due to worn parts but I can't figure out what exact parts are
> causing it. Any help would be appreciated.

Sounds like a worn chain and/or cogs to me. You may have to replace both to make it stop.

--

-John ([email protected])
 
J

John Dacey

Guest
On Sat, 3 May 2003 21:39:20 -0700, "Pat" <[email protected]> wrote:

>Hello. I have a problem with my mountainbike that's been pretty common with bikes I've had but now
>find it really irritating and want to fix it.
>
>When I put a lot of pressure on the pedal (like when I start pedaling from rest), the pedal jerkily
>advances a little bit without the wheels moving and then it "catches" and the wheels turn as the
>pedal turns. It almost feels like every link on the chain is skipping one cog but that seems
>impossible for every cog would have to be worn.
>
>When it happens, it's a jolt to the body which once in a while almost knocks me off the bike.
>
>The bike is not knew so I think it's due to worn parts but I can't figure out what exact parts are
>causing it. Any help would be appreciated.

For the problem to occur in every sprocket suggests that it's not related to chain wear. This sounds
very much like the pawls in the freehub body are sticking. Sometimes the problem can be cured by
trying to introduce some oil into the freehub body; sometimes you'll have to replace it.

-------------------------------
John Dacey Business Cycles, Miami, Florida 305-273-4440 http://www.businesscycles.com Now in our
twentieth year. Our catalog of track equipment: seventh year online
-------------------------------
 
R

Rudge

Guest
Could this be caused by a worn pawl or ratchet tooth in the freewheel mechanism? If there were 12
ratchet teeth and one was worn or faulty you would get the fault occasionally. A worn freewheel pawl
would probably be more noticeable.
 
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