Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Which Front derailleur???

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.

Which Front derailleur???

Old 04-30-18, 09:03 AM
  #1  
dave s
Senior Member
Thread Starter
 
Join Date: Oct 2008
Posts: 107
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Which Front derailleur???

Our 99 C Dale RT1000 tandem front derailleur broke today. 9 speed crank, 53/42/30 chain rings. 10 Speed in the rear, 10 speed chain.
I know that most Shimano triples are set up for 50/39/30 and I need the correct 34.9 clamp, not sure which one to look for..I have also read that there is a difference when having a 42T vs a 39 middle chain ring. Pls advise which FD I need to look for. After wading thru Shimano tech docs, it looks like a 6603, 7803, and 7803 are rated for 52T, most other triples are rated for 50/39/30, not sure about the 42T middle ring...
cross posted in Tandems
dave s is offline  
Old 04-30-18, 10:07 AM
  #2  
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 40,267

Bikes: 8

Mentioned: 179 Post(s)
Tagged: 0 Thread(s)
Quoted: 6350 Post(s)
My Guess; Road, triple [53/42\39/30] oversize band , or adapter band and a braze on FD.
I doubt the 3 more teeth on the middle ring matters mostly the arc of the outer cage is different,

more when its a 44t MTB compact triple outer..
fietsbob is offline  
Old 04-30-18, 03:17 PM
  #3  
Eggman84
Senior Member
 
Join Date: Nov 2016
Location: SoCal
Posts: 299

Bikes: 2014 Bruce Gordon Rock&Road, 1995 Santana Visa Tandem, 1990 Trek 520, 2012 Surly LHT

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 139 Post(s)
Originally Posted by dave s View Post
Our 99 C Dale RT1000 tandem front derailleur broke today. 9 speed crank, 53/42/30 chain rings. 10 Speed in the rear, 10 speed chain.
Why not replace it with what was on your tandem. Many parts are available on E-bay as New Old Stock (NOS). Used stuff also has a lot of life left as well. THe gearing on you bike, if it truely is a 99, appears to have been modified as 10 speeds were not available in 1999, it was 9 speed era so you or someone already has done some modifications if you have 10 speed rear/chain.

As far as I know, you could use a 9 speed triple FD such as a Dura Ace FD-7703, rated for 53/39/30, or Ultegra FD-6503, rated for 52/42/30 but should work for a 53T large chainring. You could even try a 10 speed triple Ultegra FD-6603, rated for 52/39/30.
Eggman84 is offline  
Old 04-30-18, 03:25 PM
  #4  
Iride01
Senior Member
 
Iride01's Avatar
 
Join Date: Jul 2017
Location: Mississippi
Posts: 2,046

Bikes: '91 Schwinn Paramount '78 Raleigh Competition GS

Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 763 Post(s)
I've never considered a triple front so please educate me if wrong. However I don't see where the size of the middle matters to the front derailleur. As long as the DR cage can accommodate the chain drop from the large to small, I'd think there'd be no issue.
Iride01 is offline  
Old 04-30-18, 08:57 PM
  #5  
SkyDog75
Senior Member
 
Join Date: May 2011
Location: Upstate NY
Posts: 3,818

Bikes: Bianchi San Mateo and a few others

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 632 Post(s)
Originally Posted by Iride01 View Post
I've never considered a triple front so please educate me if wrong. However I don't see where the size of the middle matters to the front derailleur. As long as the DR cage can accommodate the chain drop from the large to small, I'd think there'd be no issue.
STI front derailleurs are designed for a particular size difference between the middle and big ring. If the middle ring is much bigger than the derailleur was designed for, the inner plate of the derailleur may contact the middle chainring. Moving the derailleur up can buy you some clearance on the middle chainring, but then the derailleur is positioned a bit high for the big ring, not to mention it reduces the capacity for a small ring.
SkyDog75 is offline  
Old 04-30-18, 09:06 PM
  #6  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 11,364

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1650 Post(s)
The lower edge of the inner cage plate needs to clear the tops of the middle ring. So a der with too "deep/tall" an inner cage plate shape could rub an a 42T ring but clear a 39t ring. Also the cage's contours might not match where the chain is running past them if the ring was the wrong size, affecting the chain's lift during shifting. Andy
Andrew R Stewart is offline  

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.