Mavic 840/841 questions

[James Thomson]

I have a small collection of Mavic 840 and 841 derailleurs I'd like to press
into service:

http://www.bikepro.com/products/rear_derailleurs/mavic_rrder.html

Before I begin experimenting, can anyone suggest the likely capacity (max.
sprocket and max. wrap) for both?

I don't currently own any Mavic indexing levers. Can anyone suggest what
non-Mavic shifters and cassettes might work, and in what combinations?

Finally, there's a little cam with on the derailleur body between the barrel
adjuster and the cable clamp. The cable can pass through a hole in the cam,
or across its curved outer face - the intention was obviously to provide two
indexing options. Can anyone tell me what these two options were?

Thanks.

James Thomson

[bjw@mambo.ucolick.org]

On May 18, 11:40*am, Ben C <spams...@spam.eggs> wrote:
> On 2008-05-18, James Thomson <yosnap...@hotmail.com> wrote:
>
> > I have a small collection of Mavic 840 and 841 derailleurs I'd like to press
> > into service:
>
> >http://www.bikepro.com/products/rear_derailleurs/mavic_rrder.html
>
> > Before I begin experimenting, can anyone suggest the likely capacity (max.
> > sprocket and max. wrap) for both?
>
> > I don't currently own any Mavic indexing levers. Can anyone suggest what
> > non-Mavic shifters and cassettes might work, and in what combinations?
>
> So long as the shifter and cassette match I don't think it matters much
> what derailleur you have (provided it has enough capacity).
>
> Because of the little cam you can possibly even use mis-matched shifter
> and cassette with this one.

I can't figure out a context in which your advice
compiles correctly.

Unfortunately, neither you nor I know the mechanical
advantage of a Mavic derailleur - how much it moves
per cable pull. The shifter and the derailleur have to
match in order for it to move the intended cog spacing.
Then that has to match the cassette, or be fairly close.
There is a limited range of cassette spacings, so you
can sometimes shift a C wheel with an S shifter and
derailleur, but if you try to mix an S shifter and C
derailleur, you'll just get very muddled.


Based on this message from John Dacey:

http://groups.google.com/group/rec.bicycles.tech/msg/39b9b8723fa16dd0

it might work with Shimano 7-speed shifters and
cassette (in which case it might also work with
8 speed). This also informs us that the purpose
of the cam is to adjust for 6 or 7 speeds.

There are other opinions easily findable in the
archives. Sometimes, in these marginal cases,
it can help to swap in a Shimano floating upper
pulley, if it is compatible with the rear derailleur.

Ben

[Ben C]

On 2008-05-18, James Thomson <yosnappyj@hotmail.com> wrote:
> I have a small collection of Mavic 840 and 841 derailleurs I'd like to press
> into service:
>
> http://www.bikepro.com/products/rear_derailleurs/mavic_rrder.html
>
> Before I begin experimenting, can anyone suggest the likely capacity (max.
> sprocket and max. wrap) for both?
>
> I don't currently own any Mavic indexing levers. Can anyone suggest what
> non-Mavic shifters and cassettes might work, and in what combinations?
>
> Finally, there's a little cam with on the derailleur body between the barrel
> adjuster and the cable clamp. The cable can pass through a hole in the cam,
> or across its curved outer face - the intention was obviously to provide two
> indexing options. Can anyone tell me what these two options were?

I would suggest (but wait for someone who knows what he's talking about)
that if you have a matched shifter and cassette-- both Simano 8 speed or
both Campag 9 speed or something-- use the straight path. Otherwise frob
with the cam and see if you can get more gears to work that way.