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

7 speed front derailleur and 8 speed cassette

Notices
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.

7 speed front derailleur and 8 speed cassette

Old 10-03-13, 09:50 AM
  #1  
hybridbkrdr
we be rollin'
Thread Starter
 
hybridbkrdr's Avatar
 
Join Date: Oct 2009
Location: Quebec, Canada
Posts: 1,834
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 138 Post(s)
Liked 13 Times in 13 Posts
7 speed front derailleur and 8 speed cassette

I'm just curious if any of you have seen that to know if you could have chain rubbing inside the front derailleur cage when on the smallest or largest cog in the rear.

I mean I know I want an 8 speed cassette, but pondering getting a 7 speed front derailleur.
hybridbkrdr is offline  
Old 10-03-13, 09:57 AM
  #2  
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Posts: 12,055

Bikes: 2016 Hong Fu FM-079-F, 1984 Trek 660, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2016 Islabikes Beinn 20 (son's)

Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1221 Post(s)
Liked 67 Times in 47 Posts
If anything, the 7 speed front derailler will be slightly wider than the 8 speed, yielding less of a chance of rubbing at the extremes. However, you may find that front shifting is compromised by the extra cage width as I did trying to use a 7 speed front derailler and 9 speed chain. Your case is less extreme so you'll likely be fine. Plenty of 7 speed chains are exactly the same width as 8 speed chains after all.
joejack951 is offline  
Old 10-03-13, 09:58 AM
  #3  
ThermionicScott 
7-speed cultist
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 20,113

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers)

Mentioned: 88 Post(s)
Tagged: 0 Thread(s)
Quoted: 2797 Post(s)
Liked 748 Times in 525 Posts
The chain width won't be a problem, as you'd be using an 8-speed chain anyway. Depending on how cross-chained you want to get, you'll need to be able to trim the front derailleur position, but that issue isn't unique to using a 7-speed FD with an 8-speed cassette.
__________________
Originally Posted by chandltp View Post
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 10-03-13, 03:14 PM
  #4  
hybridbkrdr
we be rollin'
Thread Starter
 
hybridbkrdr's Avatar
 
Join Date: Oct 2009
Location: Quebec, Canada
Posts: 1,834
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 138 Post(s)
Liked 13 Times in 13 Posts
Originally Posted by ThermionicScott View Post
The chain width won't be a problem, as you'd be using an 8-speed chain anyway. Depending on how cross-chained you want to get, you'll need to be able to trim the front derailleur position, but that issue isn't unique to using a 7-speed FD with an 8-speed cassette.
What do you mean by trim? It's going to be used with a friction shifter anyway if that's relevant.
hybridbkrdr is offline  
Old 10-03-13, 03:34 PM
  #5  
skoda2
Senior Member
 
Join Date: Jul 2012
Location: Ocala, Florida
Posts: 256

Bikes: 74 Romic, 83 Basso, Lotto, 88 Condor, Prestige MTB, 12 Soma, Groove

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Trim is moving the shifter slightly one way or the other when in one freewheel gear to correct any chain rubbing sounds. Hope this is clear.
skoda2 is offline  
Old 10-03-13, 06:19 PM
  #6  
JiveTurkey
Low car diet
 
JiveTurkey's Avatar
 
Join Date: Aug 2007
Location: Corvallis, OR, USA
Posts: 2,407

Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by joejack951 View Post
If anything, the 7 speed front derailler will be slightly wider than the 8 speed
Not necessarily. 7- and 8-speed chains are about the same width, but the cassette/freewheel is significantly narrower for 7-speed, so a 7-speed FD can be narrower, too.
JiveTurkey is offline  
Old 10-04-13, 10:11 AM
  #7  
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Posts: 12,055

Bikes: 2016 Hong Fu FM-079-F, 1984 Trek 660, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2016 Islabikes Beinn 20 (son's)

Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 1221 Post(s)
Liked 67 Times in 47 Posts
Originally Posted by JiveTurkey View Post
Not necessarily. 7- and 8-speed chains are about the same width, but the cassette/freewheel is significantly narrower for 7-speed, so a 7-speed FD can be narrower, too.
I guess it's possible; I've never measured to confirm or deny your suspicion. I do know that 9 speed front deraillers are significantly more narrow than 7 speed, to the point where an index shifting bike won't shift properly with a 7 speed FD and 9 speed chain.

Sounds like the OP will be using friction shifters so these are all moot points for the most part. With proper limit screw settings, a friction shift bike ought to be able to use any gear combination without the chain touching the derailler and still shift properly.
joejack951 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Shinkers
Bicycle Mechanics
4
01-24-19 11:09 PM
TonyN98
Bicycle Mechanics
4
08-20-16 01:14 PM
bowlofsalad
General Cycling Discussion
14
04-05-13 03:37 PM
elunty
Bicycle Mechanics
3
06-06-10 09:39 PM

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 - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.