Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 11-25-08, 02:30 PM   #1
Andy_K 
Senior Member
Thread Starter
 
Andy_K's Avatar
 
Join Date: Jan 2008
Location: Beaverton, OR
Bikes: 2013 Kona Jake, 2015 Kona Jake the Snake, 2008 Kona Major Jake, 2013 Kona Jake the Snake, 2006 Kona Kula, 2012 Ridley Excalibur, 2001 LeMond Buenos Aires, 1984 Pinarello Gran Turismo, 1982 Trek 614, 1979 Austro-Daimler, 1974 Steyr Clubman
Posts: 8,756
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 134 Post(s)
Front derailleur question

I know this is probably a dumb question, but I'm going to ask anyway. What will happen if I try to use a front derailleur (FD-M581) that Shimano specifies as having a "min. difference between top and intermediate" of 12T with a 48/38/28 crankset?
Andy_K is offline   Reply With Quote
Old 11-25-08, 03:42 PM   #2
LarDasse74
Guest
 
Join Date: Jul 2008
Location: Grid Reference, SK
Bikes: I never learned to ride a bike. It is my deepest shame.
Posts: 3,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Don't do it. Mismatched chainrings and front derailleurs are the leading cause of getting your scrotum caught in the chain.
LarDasse74 is offline   Reply With Quote
Old 11-26-08, 06:38 PM   #3
Andy_K 
Senior Member
Thread Starter
 
Andy_K's Avatar
 
Join Date: Jan 2008
Location: Beaverton, OR
Bikes: 2013 Kona Jake, 2015 Kona Jake the Snake, 2008 Kona Major Jake, 2013 Kona Jake the Snake, 2006 Kona Kula, 2012 Ridley Excalibur, 2001 LeMond Buenos Aires, 1984 Pinarello Gran Turismo, 1982 Trek 614, 1979 Austro-Daimler, 1974 Steyr Clubman
Posts: 8,756
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 134 Post(s)
Yes, that was not helpful.

I tried Google before posting here and didn't find anything, but with a little more perseverance afterward I did find my answer. For the curious, the bottom of the derailleur cage rubs the middle ring when the big ring is in use (at least potentially).

An interesting artifact of this seems to be that you can't use anything above an Alivio-level derailleur on a crankset with 48-38-28 rings (which, of course, is probably not above Alivio level itself), and on the road side of things, you apparently can't use anything above a 105-level triple front derailleur on a 50-39-30 crankset (which is also something I was contemplating -- Ultegra 6603 FD with my FSA Gossamer triple).
Andy_K is offline   Reply With Quote
Old 11-26-08, 08:33 PM   #4
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Posts: 9,279
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 50 Post(s)
You could probably raise the DER up enough to clear the middle ring, but your shifting would "technically" be compromised.
Sometimes they'll still work fine though.
Bill Kapaun is offline   Reply With Quote
Old 11-26-08, 09:18 PM   #5
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Bikes: 1984 Trek 660, 2003 Specialized Hardrock, 2004 LOOK KG386i (RIP), 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2014 Islabikes CNOC 14 (son's)
Posts: 10,121
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 145 Post(s)
I wonder if you found my thread about this. I was trying to use a 6603 front derailler with a 52/42/30 crankset. The 10 tooth difference between the big and middle rings meant that I had to have the FD a good 6mm above the big ring to clear the middle ring due to the deep inner plate of the 6603 FD. My original solution was to use a 105 9 speed FD but this past year I swapped that for a 105 10 speed FD which shifts much nicer with the 10 speed chain. I still need to have the FD set at the max point above the big ring (~3mm) to just barely clear the middle ring but it works great so I'm not complaining.
joejack951 is offline   Reply With Quote
Old 11-26-08, 09:40 PM   #6
nivekdodge
Senior Member
 
Join Date: Jul 2008
Location: Pittsburgh
Bikes:
Posts: 475
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Wow Deja Vu I have been looking for something on this with the exact same triple. The reason is I bought a new wheelset and opted to get a new SRAM cassette and I am amazed at how well and quiet it shifts. My FD is a little lazy and noisy so I was wondering if I do new complete crank or a Dura Ace derailler??
nivekdodge is offline   Reply With Quote
Old 11-27-08, 06:10 AM   #7
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
Join Date: Feb 2004
Location: St Peters, Missouri
Bikes: Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Catrike 559, Merin Bear Valley (beater bike).
Posts: 26,625
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 91 Post(s)
Rule of thumb:

If it's a part that I already own or that I can get for free I will install it on the bike and see if I can make it work to my satisfaction. I don't charge myself labor so there's no money lost and often I learn something useful in the process.

If I'm buying a new part, or even one that's been pre-broken-in, I'll hold out for one that matches.
Retro Grouch is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 08:46 PM.