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Old 08-26-12, 04:30 AM   #1
Barchettaman
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48-38-28 crankset. Which (MTB pull ration) downpull front derailleur?

Title hopefully says it all.

Im converting a road bike to a flat bar triple.

My preferred crankset is 48-38-28 (i.e. thats whats in the parts bin).

Im going with Deore LX flat bar trigger sti shifters - came off a canti bike so they should be fine for the road calipers.

Most down pull FDs seem to max out at 44 teeth, at least the ones Im finding. Which combine a max big ring of 48+ and MTB pull ratio?

Cheers all
Simon
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Old 08-26-12, 10:44 AM   #2
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Quote:
Originally Posted by Barchettaman View Post
Title hopefully says it all.

Im converting a road bike to a flat bar triple.

My preferred crankset is 48-38-28 (i.e. thats whats in the parts bin).

Im going with Deore LX flat bar trigger sti shifters - came off a canti bike so they should be fine for the road calipers.

Most down pull FDs seem to max out at 44 teeth, at least the ones Im finding. Which combine a max big ring of 48+ and MTB pull ratio?

Cheers all
Simon
A Shimano FD-R443 should do it.
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Old 08-27-12, 03:58 AM   #3
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Thanks!
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Old 08-27-12, 04:39 AM   #4
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Originally Posted by mechBgon View Post
A Shimano FD-R443 should do it.
Isn't that a road FD? It is supposed to be used with SL-R440 shifters (which are road shifters for flat handlebars).

The Mountain FD-M770 front derailleur is rated by Shimano for both 44 and 48 big front chainrings (44-32-22 and 48-36-26).

On one bicycle I am using an Alivio FD-M413 mountain front derailleur with a 48-38-28 crankset.

Last edited by Seb71; 08-27-12 at 04:48 AM.
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Old 08-27-12, 05:09 AM   #5
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Guten Tag!

Can't you use anything from the touring line from Shimano FD-T770/FD-T780? Anything from a VSF Farhradmanufaktur Fahrrad should work right, as they all use a 48T big gear on the front?

http://www.fahrradmanufaktur.de/produkte/expedition/

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Old 08-27-12, 05:32 AM   #6
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Can't you use anything from the touring line from Shimano FD-T770/FD-T780?[/url]
FD-T780 is Dyna-Sys so I do not think that it will work with 3x9-speed Shimano mountain shifters (but I never used Dyna-Sys so I might be wrong).

I can not find FD-T770. Did you mean FD-M770? Or maybe FD-T781?
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Old 08-27-12, 08:37 AM   #7
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Originally Posted by mechBgon View Post
A Shimano FD-R443 should do it.
Good choice
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Originally Posted by Seb71 View Post
Isn't that a road FD? It is supposed to be used with SL-R440 shifters (which are road shifters for flat handlebars).
The SL-R440 shifters have the same EXACT identical pull as Shimano mountain bike shifters. As a matter of fact, a friend of mine compared his SL-R440 shiftes to a set of 9 speed Deore mountain bike shifters and the shfiter sets were identical in every way except for color. Shimano makes the 400 series of components to use mountain bike shifters of any type with road bike size gearing (48 and up) but the shifters are just color changed but otherwise the same as common mountain bike shifters.

There really aren't any mountain bike shifters that will properly move a front road derailleur correctly and have a cage that is sized for a 52t ring for example hence the need for the 400 series.

Last edited by bobotech; 08-27-12 at 09:07 AM.
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Old 08-27-12, 09:15 AM   #8
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Shimano's designation as "road shifters for flat handlebars" lead me to believe that they have "road" cable pull ratio for front derailleur/left shifter. So because of that, I assumed that the FD-R443 derailleur also has a "road" cable pull ratio. If Shimano would publish the relevant technical data (such as cable pull in millimeters) such confusions would be avoidable.
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Old 08-27-12, 09:33 AM   #9
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Originally Posted by Seb71 View Post
FD-T780 is Dyna-Sys so I do not think that it will work with 3x9-speed Shimano mountain shifters (but I never used Dyna-Sys so I might be wrong).

I can not find FD-T770. Did you mean FD-M770? Or maybe FD-T781?
this is what I mean (a middle-spec'd German tourer), sorry for the confusion:

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Old 08-27-12, 10:17 AM   #10
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Originally Posted by Seb71 View Post
Shimano's designation as "road shifters for flat handlebars" lead me to believe that they have "road" cable pull ratio for front derailleur/left shifter. So because of that, I assumed that the FD-R443 derailleur also has a "road" cable pull ratio. If Shimano would publish the relevant technical data (such as cable pull in millimeters) such confusions would be avoidable.
Totally agreed.

Just to clarify for others who might wander into this thread, I am posting a picture of a pair of roughly identical caged derailleurs. The one of the left is an road bike Ultregra FD-6503 and the one on the right is an actual FD-R443. You will see the cages are pretty identical however the main difference is the distance between the pivot point and the cable attachment points. Look at the orange line in between the yellow lines on the Ultregra derailleur and note the short distance between the yellow lines and compare to the much longer orange line in between the yellow lines on the FD-R443 derailleur. That is what makes the FD-R400 series rather special. It allows someone who wants road bike gearing (note the large cages on both of the derailleurs, designed for 48t and higher) but who wants to use mountain bike shifters which pull a lot more cable. Almost all other mountain bike derailleurs are designed for 46t and lower big rings on the front.
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Old 08-27-12, 10:26 AM   #11
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Totally agreed.

Just to clarify for others who might wander into this thread, I am posting a picture of a pair of roughly identical caged derailleurs. The one of the left is an road bike Ultregra FD-6503 and the one on the right is an actual FD-R443. You will see the cages are pretty identical however the main difference is the distance between the pivot point and the cable attachment points. Look at the orange line in between the yellow lines on the Ultregra derailleur and note the short distance between the yellow lines and compare to the much longer orange line in between the yellow lines on the FD-R443 derailleur. That is what makes the FD-R400 series rather special. It allows someone who wants road bike gearing (note the large cages on both of the derailleurs, designed for 48t and higher) but who wants to use mountain bike shifters which pull a lot more cable. Almost all other mountain bike derailleurs are designed for 46t and lower big rings on the front.
Perfect illustration

The mountain-bike hardcore weight weenies sometimes use road FDs for their low weight. To get the correct pull ratio, they use bolt-on extenders like Speen (PDF file) that move the cable anchor point farther from the pivot. If you happen to have a really good road derailleur and want to use it, there may be a Speen adapter that would do it.
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Old 08-27-12, 10:44 AM   #12
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I have a funny feeling that those Speen adapters will be really pricey.

And mountain bike weight weenies? Really? Next up: moonbike weight weenies!!
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Old 08-27-12, 02:10 PM   #13
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Better: Use the right trigger shifter and a front friction shifter of some sort, with any mech you like.
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Old 06-24-13, 02:07 AM   #14
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Update:

I got the suggested FD and it works perfectly:

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