Why are some derailers non-SIS?

Ken Pisichko

In reading Sheldon's glossary and in looking at bikes with friction and
SIS types of shift systems I would like to know why deraillers are
described as non-SIS. I don't really see why a derailler cannot be used
for indexing or friction shifting on the identical rear "gear sprocket".
What am I missing?

Phil Brown

>In reading Sheldon's glossary and in looking at bikes with friction and
>SIS types of shift systems I would like to know why deraillers are
>described as non-SIS. I don't really see why a derailler cannot be used
>for indexing or friction shifting on the identical rear "gear sprocket".
>What am I missing?

A derailleur must move a specific distance per one click of cable movement to
be compatable and the cable pull per click must be compatable as well.
Phil Brown

Dan Daniel

On Sat, 17 Apr 2004 19:58:32 -0500, Ken Pisichko <kenp@mts.net> wrote:

>In reading Sheldon's glossary and in looking at bikes with friction and
>SIS types of shift systems I would like to know why deraillers are
>described as non-SIS. I don't really see why a derailler cannot be used
>for indexing or friction shifting on the identical rear "gear sprocket".
>What am I missing?

As someone said, movement per unit of cable pull.

'SIS' is a specific term- Shimano Index System,' I believe. Other
companies have other names.

Seems to me that the surest sign that a rear derailleur is *not* meant
to be used on an indexed system is the lack of an adjustable barrel
for the cable. This is helpful for fine tuning the indexing.

Then again, it'd be interesting to add an adjustable barrel to a
non-indexed derailleur and see if it can be used with indexing.

Well, not that interesting actually.....

Werehatrack

On Sat, 17 Apr 2004 19:58:32 -0500, Ken Pisichko <kenp@mts.net> may
have said:

>In reading Sheldon's glossary and in looking at bikes with friction and
>SIS types of shift systems I would like to know why deraillers are
>described as non-SIS. I don't really see why a derailler cannot be used
>for indexing or friction shifting on the identical rear "gear sprocket".
>What am I missing?

The ratio of cable travel to derailleur motion must be an exact match
in order for the indexing to work. This is assured in the
SIS-compatible ders and shifters. It is *not* assured in others, and
mix-and-match is pretty much guaranteed not to work for those.

--
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Words processed in a facility that contains nuts.

Alex Rodriguez

In article <4081D2B8.FA14F194@mts.net>, kenp@mts.net says...

>In reading Sheldon's glossary and in looking at bikes with friction and
>SIS types of shift systems I would like to know why deraillers are
>described as non-SIS. I don't really see why a derailler cannot be used
>for indexing or friction shifting on the identical rear "gear sprocket".
>What am I missing?

The shifting mechanism will only work properly when you use compatible
components. This means the shifter, derailler and cassette have to be
matched. So when you click the shifter one click the derailleru moves
exactly the spacing of the cassette. If the derailleur is not SIS, it
means that for one click of an SIS shifter, it moves more or less than
the spacing of the cassette.
--------------
Alex