Mavic 840/841 questions

James Thomson said:

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.

James Thomson said:

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.

Ben C said:

James Thomson said:

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

Quoted message said:

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

Quoted message said:

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

Quoted message said:

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

Quoted message said:

Ben C said:

James Thomson said:

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

Quoted message said:

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

Quoted message said:

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

Quoted message said:

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.

Aha, I hadn't though of that.

<goes away and reads sheldonbrown>

This page: http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3945

explains that newer Shimano derailleurs have a shift ratio of 1.7. Newer
Campag ones have a shift ratio of 1.5.

In that case I reckon the basic point of the cam is so that the Mavic
can either operate with the same mechanical advantage (shift ratio) as
Shimano or as Campag, depending on where you route the cable. It's
probably 1.7 if you go through and 1.5 if you go around (or do I have
that the wrong way round?).

You're still supposed to have a proper matching set of sprockets and
shifters. It doesn't matter how many speeds.

But not knowing the vintage of the Mavic it may be the ratios weren't
1.7 and 1.5 in those days but 1.9 and 1.4 or something...

James Thomson said:

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?

Probably 26 for the short cage, 30/32 for the long.

Quoted message said:

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

These were compatible with shimano index shifters, all but DA 8s.

Quoted message said:

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?

7s or 8s

Quoted message said:

Thanks.

James Thomson