26/36/50: derailleur?

[Ben Arthur]

which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
this is 24t. will it work anyway? or is there another brand with larger specs?

 

[Paul Southworth]

In article <[email protected]>, ben arthur <[email protected]> wrote:
>which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
>this is 24t. will it work anyway? or is there another brand with larger specs?

Should work fine as long as the derailleur is not designed for a "compact" system (ie, do not get a
derailleur designed for 42-44t large chainrings).

I have run 24-36-50 with Shimano MTB derailleurs, works fine.

A rear derailleur that will wrap up enough chain is the more important thing. Modern Shimano MTB
derailleurs are good at this IMO.

--Paul

 

[Bruce]

Paul Southworth wrote:

>>which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
>>this is 24t. will it work anyway? or is there another brand with larger specs?
>
>
> Should work fine as long as the derailleur is not designed for a "compact" system (ie, do not get
> a derailleur designed for 42-44t

Why? Whats the difference? Apart from the curvature of the arm-thingy, which would bulge out a
little away from the arc of the large chainring. Its the vertical range thats most important. Have
you had other problems?

24T x 0.5"/T / 2pi = 1.9" radius difference. So you want at least a 2 inch vertical
movement range.

 

[Sheldon Brown]

Bruce wrote:
> Paul Southworth wrote:
>
>>> which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
>>> this is 24t. will it work anyway? or is there another brand with larger specs?
>>
>>
>>
>> Should work fine as long as the derailleur is not designed for a "compact" system (ie, do not get
>> a derailleur designed for 42-44t
>
>
> Why? Whats the difference? Apart from the curvature of the arm-thingy, which would bulge out a
> little away from the arc of the large chainring.

Bingo, that's the problem.

> Its the vertical range thats most important. Have you had other problems?
>
> 24T x 0.5"/T / 2pi = 1.9" radius difference. So you want at least a 2 inch vertical movement
> range.

You get the maximum usable vertical range when the curvature of the arm-thingy matches the curvature
of the chainring.

If the arm-thingy is made for a 42, the tail of the a-t will bump into the teeth of the chainring
while the front part is way higher than need be. Thus, you wind up with a lot of the vertical room
being wasted, placed higher than the chain can ever go.

In addition, since the working part of the arm-thingy is higher above the chainrings than it should
be, it can't create as great a chain angle for the same amount of sideways motion, so shifting will
be slow and difficult.

Nothing is optimized for a 50 tooth big ring, but the best match would be a "road triple" with the
lower front edge of the arm-thingy ground away so it will match the curvature. If you have indexed
front shifting and drop handlebars, (i.e., Shimano "road" STI) this is the best way to go.

If you have straight handlebars with indexed "mountain" type shifters, you'd be better off with a
"full-sized" "mountain" front derailer, maybe regrinding the bottom _rear_edge of the arm-thingy.
This is becasue "mountain" type front shifters move a different amount of cable compared with
"road" type.

If your front shifter is _not_ indexed, the "road" type would be best.

See also my article on this topic, http://sheldonbrown.com/derailer-adjustment.html

Sheldon "The Bench Grinder Is One Of My Favorite Tools" Brown
+--------------------------------------+
| Truth, like a torch, | the more it's shook it shines. | --Sir Wm. Hamilton |
+--------------------------------------+ 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

 

[Jeff Wills]

Bruce <[email protected]> wrote in message
news:<[email protected]>...
> Paul Southworth wrote:
>
> >>which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
> >>this is 24t. will it work anyway? or is there another brand with larger specs?
> >
> >
> > Should work fine as long as the derailleur is not designed for a "compact" system (ie, do not
> > get a derailleur designed for 42-44t
>
> Why? Whats the difference? Apart from the curvature of the arm-thingy, which would bulge out a
> little away from the arc of the large chainring. Its the vertical range thats most important. Have
> you had other problems?
>
> 24T x 0.5"/T / 2pi = 1.9" radius difference. So you want at least a 2 inch vertical movement
> range.

Bruce: the curvature is the problem. The MTB derailleurs have a smaller arc on the cage, which
causes the tail of the cage to hit the chainrings if the front of the cage is adjusted properly. The
longer "road" derailleurs will work better with this large chainring.

FWIW: I have a Shimano 105 front on a 24/38/50 crankset. It works fine. My wife has a 105 with a
24/42/52 crankset and it works fine, also. If you're going to use Shimano Rapidfire shifters, you'll
need a FD-R440 for "road" chainwheels : http://sheldonbrown.com/harris/derailers.html#front

Jeff

 

[Bruce]

Sheldon Brown wrote:

>> Why? Whats the difference? Apart from the curvature of the arm-thingy, which would bulge out a
>> little away from the arc of the large chainring.

> You get the maximum usable vertical range when the curvature of the arm-thingy matches the
> curvature of the chainring.

Oh the shame. I've read almost your entire website. But a moment of mental block, and laziness, and
I get mocked by the Man himself. I'm not worthy. Its a cage. Sorry.
http://sheldonbrown.com/gloss_c.html#cage

> If the arm-thingy is made for a 42, the tail of the a-t will bump into the teeth of the chainring
> while the front part is way higher than need be. Thus, you wind up with a lot of the vertical room
> being wasted, placed higher than the chain can ever go.

D'oh! To make matters worse, just looking at a derailer might have answered my question.

 

[Alan Walker]

[email protected] (ben arthur) wrote in message
news:<[email protected]>...
> which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
> this is 24t. will it work anyway? or is there another brand with larger specs?

Sheldon's advice is, as always, excellent, and I agree with him ipsissimis verbis, but I would like
to add one more picayune point. Shifting can be better if the middle chainwheel is closer in size to
the large chainwheel than to the small. You might get better shifting with a 38 tooth middle ring.
Over to you Sheldon.

Disclaimer: this phenomenon might only apply in the Southern Hemisphere, due to Coriolis forces. I
have never tried it up over.

 

[Qui Si Parla Ca]

bja-<< which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max
diff. this is 24t. will it work anyway? or is there another brand with larger specs?

Try to find an older XT or XTR used when big rings were 46t, instead of 42t-if no soap, let me know,
I can still get them-

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"

 

[Jeff Wills]

[email protected] (Alan Walker) wrote in message
news:<[email protected]>...
> [email protected] (ben arthur) wrote in message
> news:<[email protected]>...
> > which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max diff.
> > this is 24t. will it work anyway? or is there another brand with larger specs?
>
> Sheldon's advice is, as always, excellent, and I agree with him ipsissimis verbis, but I would
> like to add one more picayune point. Shifting can be better if the middle chainwheel is closer in
> size to the large chainwheel than to the small. You might get better shifting with a 38 tooth
> middle ring. Over to you Sheldon.
>
> Disclaimer: this phenomenon might only apply in the Southern Hemisphere, due to Coriolis forces. I
> have never tried it up over.

Ah-ha! Given that the Dura-Ace triple is 30/39/53, that would explain why Shimano will only sell it
in the Northern hemisphere! Eureka!

Jeff

 

[Matt O'Toole]

Qui si parla Campagnolo wrote:

> bja-<< which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max
> diff. this is 24t. will it work anyway? or is there another brand with larger specs?
>
> Try to find an older XT or XTR used when big rings were 46t, instead of 42t-if no soap, let me
> know, I can still get them-

Yup. I used my old DX derailer with rings as big as 50 and as small as 22, with no problems at all.
In fact, I wish my current XT setup shifted as well. An old XT is probably similar, so it's probably
a good bet.

Matt O.

 

[Mike S.]

"Sheldon Brown" <[email protected]> wrote in message
news:[email protected]...
> Bruce wrote:
> > Paul Southworth wrote:
> >
> >>> which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t max
> >>> diff. this is 24t. will it work anyway? or is there another brand with larger specs?
> >>
> >>
> >>
> >> Should work fine as long as the derailleur is not designed for a "compact" system (ie, do not
> >> get a derailleur designed for 42-44t
> >
> >
> > Why? Whats the difference? Apart from the curvature of the arm-thingy, which would bulge out a
> > little away from the arc of the large chainring.
>
> Bingo, that's the problem.
>
> > Its the vertical range thats most important. Have you had other
problems?
> >
> > 24T x 0.5"/T / 2pi = 1.9" radius difference. So you want at least a 2 inch vertical movement
> > range.
>
> You get the maximum usable vertical range when the curvature of the arm-thingy matches the
> curvature of the chainring.
>
> If the arm-thingy is made for a 42, the tail of the a-t will bump into the teeth of the chainring
> while the front part is way higher than need be. Thus, you wind up with a lot of the vertical room
> being wasted, placed higher than the chain can ever go.
>

I just had this problem setting up a 'cross bike for a friend. He brough over a mtn f.der, but was
running road rings. The inner plate of the der. hit on the 42t inner ring when shifting to the big
ring. The solution was a road f.der till he switches back to 'cross racing rings.

I've had good luck with the LX f.der shifting 22/38/50. Its a little finicky to set up, but works
fine now that the "bugs" are worked out.

> In addition, since the working part of the arm-thingy is higher above the chainrings than it
> should be, it can't create as great a chain angle for the same amount of sideways motion, so
> shifting will be slow and difficult.
>
> Nothing is optimized for a 50 tooth big ring, but the best match would be a "road triple" with the
> lower front edge of the arm-thingy ground away so it will match the curvature. If you have indexed
> front shifting and drop handlebars, (i.e., Shimano "road" STI) this is the best way to
go.
>
> If you have straight handlebars with indexed "mountain" type shifters, you'd be better off with a
> "full-sized" "mountain" front derailer, maybe regrinding the bottom _rear_edge of the arm-thingy.
> This is becasue "mountain" type front shifters move a different amount of cable compared with
> "road" type.
>
> If your front shifter is _not_ indexed, the "road" type would be best.
>
> See also my article on this topic, http://sheldonbrown.com/derailer-adjustment.html
>
Sheldon "The Bench Grinder Is One Of My Favorite Tools" Brown
> +--------------------------------------+
> | Truth, like a torch, | the more it's shook it shines. | --Sir Wm. Hamilton |
> +--------------------------------------+ 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

 

[Ben Arthur]

> This is becasue "mountain" type front shifters move a different amount of cable compared with
> "road" type.

sheldon: can you elaborate on this comment? i have a friction (i.e. non-indexed) front shifter on
the downtube (105-double circa 1990). will it work with a MTB derailleur (LX)? or is the range too
small and i won't be able to shift into the highest or smallest gear?

 

[Sheldon Brown]

ben arthur quoted me:
>>This is becasue=20 "mountain" type front shifters move a different amount of cable compare=
d=20
>>with "road" type.

and asked:

> sheldon: can you elaborate on this comment? i have a friction (i.e. non-indexed) front shifter on
> the downtube (105-double circa 1990).=20 will it work with a MTB derailleur (LX)? or is the range
> too small and i won't be able to shift into the highest or smallest gear?

This is an issue only with _indexed_ front shifters. Generally all=20 friction shifters will work
with all front derailers.

Sheldon "Friction Is Forgiving" Brown +----------------------------------------------------+
| I=92m not convinced that this was the right time | to attack Iraq, but I would like to express
| my | support for, and gratitude to U.S. and allied | fighting forces, and to wish them all
| success. |
+----------------------------------------------------+ 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

 

[Jose Rizal]

Sheldon Brown:

> Sheldon "Friction Is Forgiving" Brown +----------------------------------------------------+
> | I’m not convinced that this was the right time | to attack Iraq, but I would like to express
> | my | support for, and gratitude to U.S. and allied | fighting forces, and to wish them all
> | success. |
> +----------------------------------------------------+

You do realise that when you say you are supporting the US and others' forces in Iraq, you are
really saying that you support the US policy that got them there? Yours is a nonsensical
statement above.

And you did introduce this OT by your sig. This is merely a reply.

 

[Bruce]

Jose Rizal wrote:
> Yours is a nonsensical statement above.

Pot calling kettle?

> And you did introduce this OT by your sig. This is merely a reply.

When stopped at traffic lights, do you argue with drivers over their bumper stickers? Its just a
.signature. Please argue elsewhere.

 

[Jose Rizal]

Bruce:

> Jose Rizal wrote:
> > Yours is a nonsensical statement above.
>
> Pot calling kettle?

Eh? Strapped for relevant words are we?

>
> > And you did introduce this OT by your sig. This is merely a reply.
>
> When stopped at traffic lights, do you argue with drivers over their bumper stickers?

This isn't at the traffic lights, and it's not a bumper sticker. Although if both were true, and the
answer is yes, so what?

> Its just a .signature. Please argue elsewhere.

Funny. Perhaps you're ignorant of the fact that signatures carry messages and opinions.

 

[Raymo853]

I did once. It was a woman in a dodge Durango telling me mountain biking was immoral and
environmentally destructive. she has a Go Solar bumper sticker. I started calling her a hypocrite
with a pro Solar sticker on a 12 MPG auto.

"Bruce" <[email protected]> wrote in message
news:[email protected]...
> Jose Rizal wrote:
> > Yours is a nonsensical statement above.
>
> Pot calling kettle?
>
> > And you did introduce this OT by your sig. This is merely a reply.
>
> When stopped at traffic lights, do you argue with drivers over their bumper stickers? Its just a
> .signature. Please argue elsewhere.

 

[Mike S.]

"Matt O'Toole" <[email protected]> wrote in message
news:[email protected]...
> Qui si parla Campagnolo wrote:
>
> > bja-<< which front derailleur works for a 26/36/50 chainring setup? shimano MTB specs say 22t
> > max diff. this is 24t. will it work anyway? or is there another brand with larger specs?
> >
> > Try to find an older XT or XTR used when big rings were 46t, instead of 42t-if no soap, let me
> > know, I can still get them-
>
> Yup. I used my old DX derailer with rings as big as 50 and as small as
22,
> with no problems at all. In fact, I wish my current XT setup shifted as well. An old XT is
> probably similar, so it's probably a good bet.
>
> Matt O.
>
I got an old (early 90s!) Deore f.der. to shift fine with my 105 9s STI by running the cable the
"wrong" way 'round the attachment bolt. Seems to be a quick fix for the cable pull problem.

I do miss the ability of thumbshifters to go friction if needed, but every time I look through by
bin of parts, I wonder why I'm keeping those old XT 6s thumbshifters around... I just can't bring
myself to sell them.

Mike

 

[Matt O'Toole]

"ben arthur" <[email protected]> wrote in message
news:[email protected]...

> which front derailleur works for a 26/36/50 chainring
setup? shimano
> MTB specs say 22t max diff. this is 24t. will it work
anyway? or is
> there another brand with larger specs?

I have run 24/34/50 with an old Deore DX with no problems.
22/34/48 with the same derailer too.

Matt O.