Problem: Bike changes gears on it's own

[[email protected]]

I have a problem with my bike. When I am putting a lot of pressure on
it (going up a hill) the bike will sometimes change a gear abruptly and
jolt the bike. It will sometimes change it back and forth abruptly
while going up a hill making it tough. I forget how many gears it has
as I haven't ridden it in a while, but I think it is a 21 speed. What
could be causing this problem and how would I go about fixing it?
Thanks.

-Darren

 

[Mark Hickey]

[email protected] wrote:

>I have a problem with my bike. When I am putting a lot of pressure on
>it (going up a hill) the bike will sometimes change a gear abruptly and
>jolt the bike. It will sometimes change it back and forth abruptly
>while going up a hill making it tough. I forget how many gears it has
>as I haven't ridden it in a while, but I think it is a 21 speed. What
>could be causing this problem and how would I go about fixing it?

You probably have one of two problems...

1) there is friction where the rear derailleur shifter cable (the one
on the right) passes under the bottom bracket (crank axle). Clean and
lubricate.

2) your frame is flexible enough to change its geometry when you're
applying maximum power going up a hill. This you can live with, or
you can replace the bike/frame.

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

 

[Pat in TX]

:
>
>>I have a problem with my bike. When I am putting a lot of pressure on
>>it (going up a hill) the bike will sometimes change a gear abruptly and
>>jolt the bike. It will sometimes change it back and forth abruptly
>>while going up a hill making it tough. I forget how many gears it has
>>as I haven't ridden it in a while, but I think it is a 21 speed. What
>>could be causing this problem and how would I go about fixing it?
>
> You probably have one of two problems...
>
> 1) there is friction where the rear derailleur shifter cable (the one
> on the right) passes under the bottom bracket (crank axle). Clean and
> lubricate.
>
> 2) your frame is flexible enough to change its geometry when you're
> applying maximum power going up a hill. This you can live with, or
> you can replace the bike/frame.
>
> Mark Hickey

Maybe he is cross-chaining?

 

[[email protected]]

>
> Maybe he is cross-chaining?

Definition: Cross-chaining is using gears that put your chain at an
extreme angle causing it to "tick" your derailleur as you ride. The
gear combinations that cause this are inside front with far outside
rear or outside front with far inside rear.

I found this definition on the internet. Before the bike changes gears
on its own abruptly, I do here the ticking sound. How do I go about
changing this? I bought this bike used from my uncle who moved to
California and he has done a lot of triathlons and what not.

 

[Bill Sornson]

[email protected] wrote:
> I have a problem with my bike. When I am putting a lot of pressure on
> it (going up a hill) the bike will sometimes change a gear abruptly
> and jolt the bike. It will sometimes change it back and forth
> abruptly while going up a hill making it tough. I forget how many
> gears it has as I haven't ridden it in a while, but I think it is a
> 21 speed. What could be causing this problem and how would I go
> about fixing it? Thanks.

Try adjusting the cable tension to your rear derailleur. Tighten it a bit
by turning the "barrel adjuster" on the der a half-turn or so
(counter-clockwise) and see if it helps. (You should probably also lube the
cable like Mark suggested -- at least make sure it's moving freely in the
housings and under the BB.)

If you have a friend who knows bikes, ask him (or her) to take a look at it;
or take it to a shop for a quick tuneup. (Might even be free if it's
literally just an adjustment.)

 

[Bill Bushnell]

Mark Hickey <[email protected]> wrote:
> [email protected] wrote:

> >I have a problem with my bike. When I am putting a lot of pressure on
> >it (going up a hill) the bike will sometimes change a gear abruptly and
> >jolt the bike. It will sometimes change it back and forth abruptly
> >while going up a hill making it tough. I forget how many gears it has
> >as I haven't ridden it in a while, but I think it is a 21 speed. What
> >could be causing this problem and how would I go about fixing it?

> You probably have one of two problems...

>...

> 2) your frame is flexible enough to change its geometry when you're
> applying maximum power going up a hill. This you can live with, or
> you can replace the bike/frame.

If frame flex is causing auto-shift under pedaling loads, reinstall the derailer
cable with housing along its entire length, no un-housed cable between shifter
and derailer.

--
Bill Bushnell
http://pobox.com/~bushnell/

 

[Pat in TX]

> >
>> Maybe he is cross-chaining?
>
> Definition: Cross-chaining is using gears that put your chain at an
> extreme angle causing it to "tick" your derailleur as you ride. The
> gear combinations that cause this are inside front with far outside
> rear or outside front with far inside rear.
>
> I found this definition on the internet. Before the bike changes gears
> on its own abruptly, I do here the ticking sound. How do I go about
> changing this? I bought this bike used from my uncle who moved to
> California and he has done a lot of triathlons and what not.

The only thing you can do is not use those gear combinations. The angle of
the chain is so great that it will wear down your cogs prematurely as well
as the shifting problems.

Pat in TX
>

 

[[email protected]]

Pat in TX wrote:
> > >
> >> Maybe he is cross-chaining?
> >
> > Definition: Cross-chaining is using gears that put your chain at an
> > extreme angle causing it to "tick" your derailleur as you ride. The
> > gear combinations that cause this are inside front with far outside
> > rear or outside front with far inside rear.
> >
> > I found this definition on the internet. Before the bike changes gears
> > on its own abruptly, I do here the ticking sound. How do I go about
> > changing this? I bought this bike used from my uncle who moved to
> > California and he has done a lot of triathlons and what not.
>
> The only thing you can do is not use those gear combinations. The angle of
> the chain is so great that it will wear down your cogs prematurely as well
> as the shifting problems.
>
> Pat in TX
> >

Can I take it to a bike shop and have it regeared to stop this
"cross-chaining"?

 

[Larry Farrell]

[email protected] wrote:
> Pat in TX wrote:
>
>>>>Maybe he is cross-chaining?
>>>
>>>Definition: Cross-chaining is using gears that put your chain at an
>>>extreme angle causing it to "tick" your derailleur as you ride. The
>>>gear combinations that cause this are inside front with far outside
>>>rear or outside front with far inside rear.
>>>
>>>I found this definition on the internet. Before the bike changes gears
>>>on its own abruptly, I do here the ticking sound. How do I go about
>>>changing this? I bought this bike used from my uncle who moved to
>>>California and he has done a lot of triathlons and what not.
>>
>>The only thing you can do is not use those gear combinations. The angle of
>>the chain is so great that it will wear down your cogs prematurely as well
>>as the shifting problems.
>>
>>Pat in TX
>>
>
> Can I take it to a bike shop and have it regeared to stop this
> "cross-chaining"?
>

The problem is not related to a specific gearing
setup, it is related to the chain being at an
extreme angle between the front and rear. Riding
with the chain on the small chain wheel and the
small cog on the cluster, or on the large chain
wheel and the large cog, generates such an angle.
There is no way to change gearing that will
eliminate the problem (unless the cluster is
reduced to only 3-4 cogs, thus greatly reducing
your gearing choices).

--
Larry D. Farrell, Ph.D.
Professor of Microbiology
Idaho State University

--
Posted via a free Usenet account from http://www.teranews.com

 

[Frank Drackman]

<[email protected]> wrote in message
news:[email protected]...
>I have a problem with my bike. When I am putting a lot of pressure on
> it (going up a hill) the bike will sometimes change a gear abruptly and
> jolt the bike. It will sometimes change it back and forth abruptly
> while going up a hill making it tough. I forget how many gears it has
> as I haven't ridden it in a while, but I think it is a 21 speed. What
> could be causing this problem and how would I go about fixing it?
> Thanks.
>
> -Darren
>

Every time I had seen this it has been that the cable is a bit loose.

 

[[email protected]]

Frank Drackman wrote:
> <[email protected]> wrote in message
> news:[email protected]...
> >I have a problem with my bike. When I am putting a lot of pressure on
> > it (going up a hill) the bike will sometimes change a gear abruptly and
> > jolt the bike. It will sometimes change it back and forth abruptly
> > while going up a hill making it tough. I forget how many gears it has
> > as I haven't ridden it in a while, but I think it is a 21 speed. What
> > could be causing this problem and how would I go about fixing it?
> > Thanks.
> >
> > -Darren
> >
>
> Every time I had seen this it has been that the cable is a bit loose.

Just called the bike shop and they stated the same (cable). He said a
tune up ($35) will take care of that, unless I need a new chain as
well. Thanks for everyone's insight and I'll let you know how it went
in a couple of days. He will be able to look at it in 2 or 3 days.

-Darren

 

[Veloise]

Frank wrote:
> Every time I had seen this it has been that the cable is a bit loose.

Remember those old friction shift levers prevalent on 70's bikes? Mine
were held in place with a black plastic thumbnut. I think I remember
having a similar problem, and it was just a matter of tightening that
nut.

OP, go see your new friends at a bike shop. They'll help you out.

--Karen D.

 

[Mike Kruger]

"Larry Farrell" <[email protected]> wrote in message
news:[email protected]...
> [email protected] wrote:
>>>
>>
>> Can I take it to a bike shop and have it regeared to stop this
>> "cross-chaining"?
>>
>
> The problem is not related to a specific gearing setup, it is related to
> the chain being at an extreme angle between the front and rear. Riding
> with the chain on the small chain wheel and the small cog on the cluster,
> or on the large chain wheel and the large cog, generates such an angle.
> There is no way to change gearing that will eliminate the problem (unless
> the cluster is reduced to only 3-4 cogs, thus greatly reducing your
> gearing choices).
>
As Larry said, cross-chaining isn't something to be fixed. It's just a
characteristic of bicycles -- and probably unrelated to the original
poster's real problem.

In addition to what Mark Hickey mentioned, it could also be that the
derailleur spring doesn't have enough spring in it, so that there is less
chain wrapped around the rear gear wheels than desirable. This can
sometimes be adjusted, and sometimes the derailleur may just need a good
cleaning -- or, you may need a new rear derailleur, which isn't the end of
the world.

 

[Bill Sornson]

[email protected] wrote:
> Frank Drackman wrote:

> Every time I had seen this it has been that the cable is a bit loose.

> Just called the bike shop and they stated the same (cable). He said a
> tune up ($35) will take care of that, unless I need a new chain as
> well. Thanks for everyone's insight and I'll let you know how it went
> in a couple of days. He will be able to look at it in 2 or 3 days.

Try increasing the cable tension yourself first. Turn the little barrel
adjuster on the rear derailleur about a half turn /counter/ clockwise. Test
ride. Fixed? You just saved $35.00.