Tech question on MTB derailleur

amirm said:

Hi all:
I need some education on front derailleurs. In particular, I want to
know about the swing mechanism. What's the difference between top and
bottom swing? What difference does it make? How can I work out mine is
top or bottom swing?
I have a Deore derailleur, and as part of upgrading the drivetrain, I
want to put a new XT. The seller asks me to specify the swing type.
Obviously, I'm not buying the part at my LBS. Can someone help?
Cheers, Amir.

Never mind, I worked it out. Mine is a top swing.

Cheers.

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amirm said:

Never mind, I worked it out. Mine is a top swing.
Cheers.

shouldnt it be 'top-pull' or bottom-pull' ???

ie which orientation the cable pulls on the mech from

From my (albeit totally un-researched and off the cuff) memory it would
seem that the majority of mtb front mechs are top-pull to keep the cable
protected from mud/road-grime if it were going round under the BB

anyone wanna clarify that?

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Nope. Bottom-pull derailleurs can be either top swing or bottom swing.
eg the Deore XT FD-M750 and FD-M751.

Nick

flyingdutch said:

amirm said:

Never mind, I worked it out. Mine is a top swing.
Cheers.

shouldnt it be 'top-pull' or bottom-pull' ???

flyingdutch said:

shouldnt it be 'top-pull' or bottom-pull' ???
ie which orientation the cable pulls on the mech from
From my (albeit totally un-researched and off the cuff) memory it would
seem that the majority of mtb front mechs are top-pull to keep the cable
protected from mud/road-grime if it were going round under the BB
anyone wanna clarify that?

You're right about the routing. However, some manufacturers still prefer
routing through the down tube and under BB (including mine). Shimano has
recently moved to make dual pull structure which one mech can be used in
either way.

However, top and bottom swing refers to the position of the swing arm
in refernce to the clamp. Due to space restriction, eg in duallies and
some compact frames, top swing mech has become popular as the clamp
can sit really close to BB. Shimano manufacture two versions of each
front derailleurs which are both dual pull and multi-clamp. That is,
they can fit any of the three mainstream seat tube sizes and they can
use either routing direction. The difference is only in the swing
geometry. A traditional hard-tail should be able to use either
version. In my case, I am going with the M760 derailleur which is top
swing. M761 is bottom swing.

It seems swing geometry has not been an issue on roadies, and they all
seem to use the bottom-pull bottom-swing set up.

Hope this clarifies a little.

Cheers, Amir.

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"amirm" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

However, top and bottom swing refers to the position of the swing arm
in refernce to the clamp. Due to space restriction, eg in duallies and
some compact frames, top swing mech has become popular as the clamp
can sit really close to BB.

<snip>

Quoted message said:

The difference is only in the swing geometry.

There's more to it than that, as some derailleurs are BB mounted with no
clamp, bottom swing and cable routing under the BB. These are used for
dualies with an interupted/minimal seat tube where a clamp-mount cannot be
used.

Cheers
Peter

Peter Signorini said:

"amirm" <[email hidden]> wrote in message news:OgJcc.12-
[email hidden]:[email hidden]-
etserver.com...

Quoted message said:

However, top and bottom swing refers to the position of the swing arm
in refernce to the clamp. Due to space restriction, eg in duallies and
some compact frames, top swing mech has become popular as the clamp
can sit really close to BB.

<snip>

Quoted message said:

The difference is only in the swing geometry.

There's more to it than that, as some derailleurs are BB mounted with
no clamp, bottom swing and cable routing under the BB. These are used
for dualies with an interupted/minimal seat tube where a clamp-mount
cannot be used.
Cheers Peter

Peter:

It's interesting you said that. Someone also said that in general bottom
swing shifts better than top swing. So when this third group of BB-
mounted derailleurs came around, they went for bottom swing and not top
swing. This is consistent with road bikes using bottom swing. So one can
conclude that top swing is a solution to address restricted requirements
of specific set-ups, eg duallies, and it's not necessarily as good.

Cheers, Amir.

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Boy, that Singlespeed is lookin' good 😄 😄 😄

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