Biggest ring with Top-Swing deraileur?

rocketman58 said:

I'm running an old XTR 110mm bolt pattern crank with 46,34,21 rings
(21 via an adaptor). The front deraileur cable stop on the seat tube
of my frame is designed to use be used with a Top Swing deraileur. I
can not get the Top Swing deraileur to shift to the 46 tooth - I
guess the 44 tooth max limit is true?

I can not use a top pull bottom swing (rated to 48 tooth max)
deraileur since the cable stop is angled in the wrong direction -
the cable exits the cable stop at a 40 degree angle on the way to the
bottom swing deraileur. (I have a 14" frame - there is little
distance from the stop to the deraileur)

Bottom line: If I swap the 46 with a 44 (44, 34, 21) will this work
with the top swing deraileur? Wanted to know before I spend the cash
on a 44 ring.

A 2 tooth difference in chainring size will change the chainring radius
by 1/6 of an inch (4 mm.)

That may or may be enough to let it work for you.

If not, I've had good success modifying front derailers by holding them
up against a bench grinding wheel, removing material from the bottom of
the outer cage plate. The idea is to make the botto edge of the outer
plate match the curvature of the chainring you'll be using.

This is the best solution I've found for getting front derailers to work
well with a different sized big chainring than they were designed for.

Sheldon "Sparky" Brown
+----------------------------------+
| Good health is nothing but the |
| slowest way to die. -Les Barker |
+----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon,

The curve of the outside plate is not the problem. In fact it looks
just fine. The problem is that the top swing deraileur will not pick
the chain up off the middle 34 ring and place it onto the 46 ring
without extream effort. I belive it has something to do with the
shape of the inner cage. A bottom swing deraileur shifts just fine,
but correct cable routing is not possible with my frame.

Should the Top Swing deraileur work ok if I swap the 46 for a 44?
will it shift from a 34 to a 44? Or do I need a 12 tooth difference
(32,44)?

Rocketman58

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

A 2 tooth difference in chainring size will change the chainring radius
by 1/6 of an inch (4 mm.)

That may or may be enough to let it work for you.

If not, I've had good success modifying front derailers by holding them
up against a bench grinding wheel, removing material from the bottom of
the outer cage plate. The idea is to make the botto edge of the outer
plate match the curvature of the chainring you'll be using.

This is the best solution I've found for getting front derailers to work
well with a different sized big chainring than they were designed for.

Sheldon "Sparky" Brown
+----------------------------------+
| Good health is nothing but the |
| slowest way to die. -Les Barker |
+----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Quoted message said:

rocketman58 said:

I'm running an old XTR 110mm bolt pattern crank with 46,34,21 rings
(21 via an adaptor). The front deraileur cable stop on the seat tube
of my frame is designed to use be used with a Top Swing deraileur. I
can not get the Top Swing deraileur to shift to the 46 tooth - I
guess the 44 tooth max limit is true?

I can not use a top pull bottom swing (rated to 48 tooth max)
deraileur since the cable stop is angled in the wrong direction -
the cable exits the cable stop at a 40 degree angle on the way to the
bottom swing deraileur. (I have a 14" frame - there is little
distance from the stop to the deraileur)

Bottom line: If I swap the 46 with a 44 (44, 34, 21) will this work
with the top swing deraileur? Wanted to know before I spend the cash
on a 44 ring.

I had the same problem when I try to replace a Shimano Altus crankset
with a Specialized Strongarm. Later I realized that the square spindle
of the bottom bracket is too long (120+ mm). While it work fine with
Altus, the Strongarm is pushed further out and the deraileur just
can't push the chain far enough to reach the 44T chainring.

In this case, how do I determine what's the right spindle length?
should the middle ring(32T) on the crank always line up with the
middle cog (4th or 5th) on the 8 speed cassette?

Thanks for any advice!

Jay

[email hidden] (rocketman58) wrote in message news:<[email hidden]>...

Quoted message said:

Sheldon,

The curve of the outside plate is not the problem. In fact it looks
just fine. The problem is that the top swing deraileur will not pick
the chain up off the middle 34 ring and place it onto the 46 ring
without extream effort. I belive it has something to do with the
shape of the inner cage. A bottom swing deraileur shifts just fine,
but correct cable routing is not possible with my frame.

Should the Top Swing deraileur work ok if I swap the 46 for a 44?
will it shift from a 34 to a 44? Or do I need a 12 tooth difference
(32,44)?

Rocketman58

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

A 2 tooth difference in chainring size will change the chainring radius
by 1/6 of an inch (4 mm.)

That may or may be enough to let it work for you.

If not, I've had good success modifying front derailers by holding them
up against a bench grinding wheel, removing material from the bottom of
the outer cage plate. The idea is to make the botto edge of the outer
plate match the curvature of the chainring you'll be using.

This is the best solution I've found for getting front derailers to work
well with a different sized big chainring than they were designed for.

Sheldon "Sparky" Brown
+----------------------------------+
| Good health is nothing but the |
| slowest way to die. -Les Barker |
+----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Quoted message said:

rocketman58 said:

I'm running an old XTR 110mm bolt pattern crank with 46,34,21 rings
(21 via an adaptor). The front deraileur cable stop on the seat tube
of my frame is designed to use be used with a Top Swing deraileur. I
can not get the Top Swing deraileur to shift to the 46 tooth - I
guess the 44 tooth max limit is true?

I can not use a top pull bottom swing (rated to 48 tooth max)
deraileur since the cable stop is angled in the wrong direction -
the cable exits the cable stop at a 40 degree angle on the way to the
bottom swing deraileur. (I have a 14" frame - there is little
distance from the stop to the deraileur)

Bottom line: If I swap the 46 with a 44 (44, 34, 21) will this work
with the top swing deraileur? Wanted to know before I spend the cash
on a 44 ring.

Jay Lu said:

I had the same problem when I try to replace a Shimano Altus crankset
with a Specialized Strongarm. Later I realized that the square spindle
of the bottom bracket is too long (120+ mm). While it work fine with
Altus, the Strongarm is pushed further out and the deraileur just
can't push the chain far enough to reach the 44T chainring.

In this case, how do I determine what's the right spindle length?
should the middle ring(32T) on the crank always line up with the
middle cog (4th or 5th) on the 8 speed cassette?

See: http://sheldonbrown.com/chainline

Sheldon "47.5 mm" Brown
+------------------------------------------------+
| I’ll be appearing in: |
| Gilbert & Sullivan's Iolanthe at M.I.T. |
| November 12, 13, 14 and 18, 19, 20, 21 |
| http://web.mit.edu/gsp/www |
| http://sheldonbrown.com/music.html |
+------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

After reading posts here and on other groups, and from my own
experience, I have decided to dump the Top Swing, and use the Bottom
swing. Advice among most was that the Top Swing just does not work as
well as the Bottom Swing. I have to agree. It is not as forgiving as
the Bottom Swing if you stray from Shimano's recommended ring sizes.

I solved the front deraileur boss problem by adapting an old deraileur
clamp to act as an alternate cable stop. I have since found that
"Problem Solvers" offers such a device - since it looks a lot better
than my prototype, I will be ordering one soon. Since I ride both on
and off road (two sets of wheels and tires), I may go to a 48,34,21
ring setup. The Bottom Swing will still handle this with no probelm.
By the way, I have a friction front thumb shifter so there is no
problem with indexing.

Thanks everyone.
Rocketman58

[email hidden] (rocketman58) wrote in message news:<[email hidden]>...

Quoted message said:

Sheldon,

The curve of the outside plate is not the problem. In fact it looks
just fine. The problem is that the top swing deraileur will not pick
the chain up off the middle 34 ring and place it onto the 46 ring
without extream effort. I belive it has something to do with the
shape of the inner cage. A bottom swing deraileur shifts just fine,
but correct cable routing is not possible with my frame.

Should the Top Swing deraileur work ok if I swap the 46 for a 44?
will it shift from a 34 to a 44? Or do I need a 12 tooth difference
(32,44)?

Rocketman58

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

A 2 tooth difference in chainring size will change the chainring radius
by 1/6 of an inch (4 mm.)

That may or may be enough to let it work for you.

If not, I've had good success modifying front derailers by holding them
up against a bench grinding wheel, removing material from the bottom of
the outer cage plate. The idea is to make the botto edge of the outer
plate match the curvature of the chainring you'll be using.

This is the best solution I've found for getting front derailers to work
well with a different sized big chainring than they were designed for.

Sheldon "Sparky" Brown
+----------------------------------+
| Good health is nothing but the |
| slowest way to die. -Les Barker |
+----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Quoted message said:

rocketman58 said:

I'm running an old XTR 110mm bolt pattern crank with 46,34,21 rings
(21 via an adaptor). The front deraileur cable stop on the seat tube
of my frame is designed to use be used with a Top Swing deraileur. I
can not get the Top Swing deraileur to shift to the 46 tooth - I
guess the 44 tooth max limit is true?

I can not use a top pull bottom swing (rated to 48 tooth max)
deraileur since the cable stop is angled in the wrong direction -
the cable exits the cable stop at a 40 degree angle on the way to the
bottom swing deraileur. (I have a 14" frame - there is little
distance from the stop to the deraileur)

Bottom line: If I swap the 46 with a 44 (44, 34, 21) will this work
with the top swing deraileur? Wanted to know before I spend the cash
on a 44 ring.