? To Measure Cog Wear

[A Muzi]

-snip worn cogs-
thejen12 wrote:
> Is a skipping chain the only sign of a worn-out cassette or cog? My
> chain doesn't skip, but my drive train seems a bit noisy and no amount
> of adjustment on the front helps (I have bar end shifters and infinite
> adjust of the chain-line on the front chainrings). The chain is
> pretty new, so I've been wondering if it's time to replace the
> cassette. Lubing helps some, but only for 20 miles or so. Also, it's
> noisier in some cogs than others.

No snappy answers to 'noisy' but check the chain wear with a steel rule
and sight the rear changer (with your head directly behind it) in a
middle gear to see if the cage is parallel to the front rings. A bent
rear changer/mounting tab is a common source of noise. Could be other
things as well but those are common.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[Ben C]

On 2007-05-10, A Muzi <[email protected]> wrote:
>> Ryan Cousineau wrote:
>>> We traded the first one for much better shifting, and the last two are
>>> rendered a little silly when you realize a 9 or 10-speed 11-25
>>> probably has every ratio Eddy ever used in any road race he ever did,
>>> plus one or two he didn't yet have.
>
> M-gineering wrote:
>> Nope, it doesn't have an 18, which was a definite 'must have' cog
>
> Yup. Even my six speed as a 17 and an 18 in the middle.

I changed from a 23-12 to a 23-13 (9-speed) which now has an 18. The 18
is used _much_ more than the 12 ever was.

 

[[email protected]]

On May 9, 8:14 pm, "Jay - BFri Commuter" <[email protected]> wrote:
> "John Henderson" <[email protected]> wrote in message
>
> news:[email protected]...
>
>
>
> >A Muzi wrote:
>
> >> I do not believe any measuring tool, at least none I've seen,
> >> can tell you that. An accurate cog wear measuring tool would
> >> have to allow for each brand in each tooth size; not likely.
>
> > This was my first thought as well. But having looked at the
> > Rohloff tool, I see it's just a piece of chain with a lever for
> > simulating peddling pressure. If this new-spec chain sits
> > deeply enough into sprocket wear pockets under pressure, the
> > end link won't slip between adjoining teeth easily.
>
> > That's an accurate test, exactly mimicing reality. The only
> > unknown variable is the new chain itself. I've found that some
> > brands are a little more inclined to skip than others.
>
> > John
>
> So it appears this tool has nothing to offer. If the new chain skips on the
> repair stand, and it did not skip previously, replace cassette. And pocket
> the $25, which was not spent on the tool.

ISTM that the tool does have something to offer. With the bike on the
repair stand and no Rohloff tool, there's usually no practical way to
apply sufficient chain tension to pull the chain forward on the worn
links and demonstrate that it will skip.

I've had many times when old cogs seemed perfect on the repair stand
or when riding with light pedaling force, but caused skipping when I
stood and sprinted hard. This tool is designed to detect that
condition.

- Frank Krygowski

 

[still me]

On 10 May 2007 08:24:45 -0700, [email protected] wrote:

>ISTM that the tool does have something to offer. With the bike on the
>repair stand and no Rohloff tool, there's usually no practical way to
>apply sufficient chain tension to pull the chain forward on the worn
>links and demonstrate that it will skip.
>
>I've had many times when old cogs seemed perfect on the repair stand
>or when riding with light pedaling force, but caused skipping when I
>stood and sprinted hard. This tool is designed to detect that
>condition.
>

I would agree to an extent. The only chains I ever saw skip on a stand
were the ones with a tight link. The others all needed a road test.
Not a "balls to the wall" test, but just a fair amount of pressure.
So, if the tool can simulate road pressure, it could be a time saver.

 

[Paul Kopit]

On Wed, 09 May 2007 20:41:02 -0500, A Muzi <[email protected]>
wrote:

>
>No snappy answers to 'noisy' but check the chain wear with a steel rule
>and sight the rear changer (with your head directly behind it) in a
>middle gear to see if the cage is parallel to the front rings. A bent
>rear changer/mounting tab is a common source of noise. Could be other
>things as well but those are common.

I've thought about this a while. I'm used to be a scientist but never
an engineer. If one took a new cog and inked the ends of the teeth on
something like an ink pad and then rolled the ink onto paper, couldn't
you somehow measure or observe the cog wear?

 

[[email protected]]

Paul Kopit writes:

>> No snappy answers to 'noisy' but check the chain wear with a steel
>> rule and sight the rear changer (with your head directly behind it)
>> in a middle gear to see if the cage is parallel to the front rings.
>> A bent rear changer/mounting tab is a common source of noise.
>> Could be other things as well but those are common.

> I've thought about this a while. I'm used to be a scientist but
> never an engineer. If one took a new cog and inked the ends of the
> teeth on something like an ink pad and then rolled the ink onto
> paper, couldn't you somehow measure or observe the cog wear?

That would give you a dashed line that cannot tell anything about the
tooth face wear that would probably not even change the dashed line
even with severe wear. You must have seen a picture of a worn
sprocket whose tooth tips were the same as a new one but having round
pockets worn into the upper face of the teeth.

Scroll down on this page to the sprocket with missing teeth. Its
tooth tips are still the same as a new one but the tooth profile is
shot.

http://pardo.net/bike/pic/fail-002/000.html

Jobst Brandt

 

[AndyMorris]

Derk wrote:
> http://www.rohloff.de/en/products/hgigcheck/index.html
> http://www.rohloff.de/en/products/hgigcheck/handling/index.html
>
> Derk

When I looked up how to use this tool

http://www.rohloff.de/fileadmin/roh...bung/hgig_check/beschreibung_hgigcheck.en.pdf

It looks very neat, but could you not do much the same with a normal chain
whip?


--
Andy Morris

AndyAtJinkasDotFreeserve.Co.UK

Love this:
Put an end to Outlook Express's messy quotes
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