rear wheel cassette wobble



All,

I know that cassette wobble on bicycles is nothing new. It's not a
bent axle (seems like most like to blame that for starters). So, I ran
an experiment.

I had a set of wheels that had varying degrees of cassette wobble and
one that had none. I put them in the truing stand and spun the wheel,
while keeping the cassette mechanism (no actual gears) still, and
watched the wobble. I then took the best cassette mechanism and put it
on the worst wobbling wheel and the worst wobbling cassette mechanism
and put it on the best wheel. The result was the wobble followed the
rim and not the cassette mechanism. I even went as far as to switch
the steel washers around and rotated them to new positions to verify
that it's not the washers.

My question is does anyone know what is causing the hub to behave like
it's mis-aligned when mated to the cassette mechanism? Is it possible
that all hubs start out true and lose that truness when a wheel is
build and stress relieved (do the hubs bend slightly - road bike hubs
especially)? Is it possible that all hubs start out with varying
degrees of truness based on machining and thermal aging cycles? Any
other possibilities?

I know this is a don't care. It's more of a technical curiosity for
me.

Thanks,
GM
 
[email protected] wrote:
> All,
>
> I know that cassette wobble on bicycles is nothing new. It's not a
> bent axle (seems like most like to blame that for starters). So, I ran
> an experiment.
>
> I had a set of wheels that had varying degrees of cassette wobble and
> one that had none. I put them in the truing stand and spun the wheel,
> while keeping the cassette mechanism (no actual gears) still, and
> watched the wobble. I then took the best cassette mechanism and put it
> on the worst wobbling wheel and the worst wobbling cassette mechanism
> and put it on the best wheel. The result was the wobble followed the
> rim and not the cassette mechanism. I even went as far as to switch
> the steel washers around and rotated them to new positions to verify
> that it's not the washers.
>
> My question is does anyone know what is causing the hub to behave like
> it's mis-aligned when mated to the cassette mechanism? Is it possible
> that all hubs start out true and lose that truness when a wheel is
> build and stress relieved (do the hubs bend slightly - road bike hubs
> especially)? Is it possible that all hubs start out with varying
> degrees of truness based on machining and thermal aging cycles? Any
> other possibilities?
>
> I know this is a don't care. It's more of a technical curiosity for
> me.
>
> Thanks,
> GM
>

it's almost certainly optical illusion. the ramps on the cassette
sprockets are sloped depending on position to assist shifting. this
gives the teeth tips the appearance of sloping one way at one part of
the circumference, the opposite at another. if you hold a pointer [like
a dead spoke] /between/ sprockets as they rotate, you'll see that the
sprockets themselves rotate true.
 
jim beam wrote:
> [email protected] wrote:
> > All,
> >
> > I know that cassette wobble on bicycles is nothing new. It's not a
> > bent axle (seems like most like to blame that for starters). So, I ran
> > an experiment.
> >
> > I had a set of wheels that had varying degrees of cassette wobble and
> > one that had none. I put them in the truing stand and spun the wheel,
> > while keeping the cassette mechanism (no actual gears) still, and
> > watched the wobble. I then took the best cassette mechanism and put it
> > on the worst wobbling wheel and the worst wobbling cassette mechanism
> > and put it on the best wheel. The result was the wobble followed the
> > rim and not the cassette mechanism. I even went as far as to switch
> > the steel washers around and rotated them to new positions to verify
> > that it's not the washers.
> >
> > My question is does anyone know what is causing the hub to behave like
> > it's mis-aligned when mated to the cassette mechanism? Is it possible
> > that all hubs start out true and lose that truness when a wheel is
> > build and stress relieved (do the hubs bend slightly - road bike hubs
> > especially)? Is it possible that all hubs start out with varying
> > degrees of truness based on machining and thermal aging cycles? Any
> > other possibilities?
> >
> > I know this is a don't care. It's more of a technical curiosity for
> > me.
> >
> > Thanks,
> > GM
> >

> it's almost certainly optical illusion. the ramps on the cassette
> sprockets are sloped depending on position to assist shifting. this
> gives the teeth tips the appearance of sloping one way at one part of
> the circumference, the opposite at another. if you hold a pointer [like
> a dead spoke] /between/ sprockets as they rotate, you'll see that the
> sprockets themselves rotate true.

There is no cassette installed (no gears) and the mechanism is not
spinning - only the wheel is spinning. The splined cylinder is
wobbling. When you're home, lift up the rear wheel and crank the
pedals a few times to get it spinning at a good rate. Then stop the
pedals and watch the cassette (it's not spinning at this point).
You'll see what I'm talking about. If you don't, you've got a hub
without a wobble.

I'm just trying to understand the origin of this wobble. Whether it's
a manufacturing process that's not easily controlled, or a
characteristic that shows up after the wheel is built up.

Thanks, GM
 
<[email protected]> wrote in message
news:[email protected]...
>

<snip>
> > it's almost certainly optical illusion. the ramps on the cassette
> > sprockets are sloped depending on position to assist shifting. this
> > gives the teeth tips the appearance of sloping one way at one part

of
> > the circumference, the opposite at another. if you hold a pointer

[like
> > a dead spoke] /between/ sprockets as they rotate, you'll see that

the
> > sprockets themselves rotate true.

> There is no cassette installed (no gears) and the mechanism is not
> spinning - only the wheel is spinning. The splined cylinder is
> wobbling. When you're home, lift up the rear wheel and crank the
> pedals a few times to get it spinning at a good rate. Then stop the
> pedals and watch the cassette (it's not spinning at this point).
> You'll see what I'm talking about. If you don't, you've got a hub
> without a wobble.
>
> I'm just trying to understand the origin of this wobble. Whether it's
> a manufacturing process that's not easily controlled, or a
> characteristic that shows up after the wheel is built up.
>
> Thanks, GM
>


I've seen it frequently in cheap old freewheels too. They seemed to work
Ok so I never took the time to figure out what the cause was.

Chas.
 
On 11 Sep 2006 16:31:27 -0700, [email protected] wrote:

>All,
>
>I know that cassette wobble on bicycles is nothing new. It's not a
>bent axle (seems like most like to blame that for starters). So, I ran
>an experiment.
>
>I had a set of wheels that had varying degrees of cassette wobble and
>one that had none. I put them in the truing stand and spun the wheel,
>while keeping the cassette mechanism (no actual gears) still, and
>watched the wobble. I then took the best cassette mechanism and put it
>on the worst wobbling wheel and the worst wobbling cassette mechanism
>and put it on the best wheel. The result was the wobble followed the
>rim and not the cassette mechanism. I even went as far as to switch
>the steel washers around and rotated them to new positions to verify
>that it's not the washers.
>
>My question is does anyone know what is causing the hub to behave like
>it's mis-aligned when mated to the cassette mechanism? Is it possible
>that all hubs start out true and lose that truness when a wheel is
>build and stress relieved (do the hubs bend slightly - road bike hubs
>especially)? Is it possible that all hubs start out with varying
>degrees of truness based on machining and thermal aging cycles? Any
>other possibilities?
>
>I know this is a don't care. It's more of a technical curiosity for
>me.


Proving that there's nothing new on r.b.t, here's a thread on the
exact same subject from 1996:

http://tinyurl.com/ezux9



jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3
 
There is a certain amount of play between the cassete and the hub. If
you loosen the bolt joining the two and then tighten it back up you
will have to retrue your wheel. The worse hubs for this are the XT
series they have a steel insert where the bolt goes in.