HOT: Active* forum members generally gain 5% discount at starbike.com store!
Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Articles FAQ Contact About




Post new topic Reply to topic  [ 15 posts ] 
Author Message
PostPosted: Thu Oct 03, 2013 9:54 am 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
It appears that no matter what I do, I can't get my Shimano front derailleur adjusted properly despite having done this plenty of times in the past with good results.

When I shift to the inner chainring & most inward cassette sprocket, the chain rubs against the inside of the derailleur arm, without cable tension and inner limit fully unscrewed. It is like the front derailleur is too narrow.

I've tried to set it higher than needed & adjusted yaw angle to the extent that the braze-on attachment allows, but then I instead get "opposite" scraping when riding the large chainring and small sprocket. What can I do here?


Top
 Profile  
 
PostPosted: Thu Oct 03, 2013 8:57 pm 
Offline

Joined: Tue Nov 11, 2003 9:47 pm
Posts: 1705
Location: Santa Cruz, California, USA
Have you measured the chain line? http://sheldonbrown.com/chainline.html

Which crank, bb, derailleur, chain, cassette?

How long is the frame's chainstays? Short frames have larger chain angles.


Top
 Profile  
 
Posted: Thu Oct 03, 2013 8:57 pm 


Top
  
 
PostPosted: Thu Oct 03, 2013 9:17 pm 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
eric wrote:
Have you measured the chain line? http://sheldonbrown.com/chainline.html" onclick="window.open(this.href);return false;

Which crank, bb, derailleur, chain, cassette?

How long is the frame's chainstays? Short frames have larger chain angles.



Frame is a 54cm Cervelo with 399 mm chainstays. Chain line is about 44mm (centre of frame to centre of big chainring)
Crank: Rotor 3D
Front derailleur: 105 5700
Chain: DA 7900
Cassette: Ultegra 6700 12-23 - with one spacer between hub and largest sprocket
BB: DA 9000 & 105 5700 - no difference
Chainrings: 5700 & Rotor QXL - no difference

I just purchased a bag of chainring spacers that perhaps would allow me to angle the FD inwards to clear the inner chainring whilst spacing the large chainring outwards. That could maybe be a start?


Top
 Profile  
 
PostPosted: Fri Oct 04, 2013 10:22 am 
Offline

Joined: Fri May 25, 2007 6:43 pm
Posts: 1914
Chainline sounds a bit narrow?
Thought shimano double was 43,5, 44mm to the outer will give you *about* a 40 mm chainline, might be too narrow for the 105 front mech. Might need to grind a bit off the front mech stop or body (or, if its still resting on the screw, take a couple of mm off the end.)
Twisting the front mech to clear will just give you a rub somewhere else, raising it will give you poor shifting. So those are two options i'd not bother pursuing too far.

An other alternative (that i've done with some MTB mechs, on botched together systems) is to locally tweak the inner front mech cage, just to give yourself an extra mm or two.


Top
 Profile  
 
PostPosted: Fri Oct 04, 2013 10:47 am 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
mattr wrote:
Chainline sounds a bit narrow?
Thought shimano double was 43,5, 44mm to the outer will give you *about* a 40 mm chainline, might be too narrow for the 105 front mech. Might need to grind a bit off the front mech stop or body (or, if its still resting on the screw, take a couple of mm off the end.)
Twisting the front mech to clear will just give you a rub somewhere else, raising it will give you poor shifting. So those are two options i'd not bother pursuing too far.

An other alternative (that i've done with some MTB mechs, on botched together systems) is to locally tweak the inner front mech cage, just to give yourself an extra mm or two.


I looked it up - my front derailleur has a specified chainline by Shimano of 43,5mm and the crankset specified at 44,5, so this might very well be the cause of the issue.


Last edited by jockster on Sun Oct 06, 2013 9:29 pm, edited 2 times in total.

Top
 Profile  
 
PostPosted: Fri Oct 04, 2013 12:45 pm 
Offline

Joined: Thu Mar 08, 2012 3:20 pm
Posts: 103
Yep seen this before, especially with same setup as you (Rotor, Cervelo and Shimano).

Look for what's blocking the FD from moving more (not always the limit) and use a dremel.


Top
 Profile  
 
PostPosted: Fri Oct 04, 2013 2:03 pm 
Offline

Joined: Fri May 25, 2007 6:43 pm
Posts: 1914
Could be it then.
I used to work on a Metron TT bike years ago that we had masses of issues with, as the shape of the frame meant that the front mech wouldn't even shift onto the small ring most of the time. Too much monocoque in the way!
IIRC we ended up filing a couple of mm of metal off the back of the mech to allow it to swing further over.


Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 8:12 am 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
What do you guys think about using a triple front derailleur instead?
Triple FD's from Shimano are built for 45mm chainline which is only .5mm away from my cranksets chainline.


Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 10:39 am 
Offline

Joined: Fri May 25, 2007 6:43 pm
Posts: 1914
Chainline is in the middle of the two rings, (or middle ring of three). Not on the CL of the outer.

So a triple mech won't help much, you need to find out what is stopping it moving inboard, is it the body of the mech, the linkages, the stops? (the frame?)
Then dremel a bit off. So it can swing in another couple of mm.

Or get the chainline right.


Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 6:17 pm 
Offline

Joined: Tue Jun 07, 2005 3:32 pm
Posts: 474
is it a BB30 or similar?
If not, and this may sound like butchery in this forum, but what about shimming out the right cup with a 1mm shim?
I've done this on one old-ish frame, because the small chainring rubbed on the stay


Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 6:36 pm 
Offline
User avatar

Joined: Fri Apr 04, 2008 2:49 am
Posts: 1259
jockster wrote:
It is like the front derailleur is too narrow.
Bend the cage to be wider? I recommend to do this carefully though, should you go that route. I've done it before and it always worked.

_________________
RideWert.com
Wert Cycling on Facebook


Top
 Profile  
 
PostPosted: Mon Oct 07, 2013 7:45 pm 
Offline

Joined: Fri Mar 18, 2005 4:12 pm
Posts: 2309
Location: eh?
Heard about this before with some cervelo's.

Ironic perhaps but the 10 speed Sram Red Yaw FD would probably solve the problem. It's the only FD that I have ever used that had no rubbing in any gear combinations.

(This assumes you are using compatible shifters.)

_________________
swinter wrote:
Mr.Gib got it right


Top
 Profile  
 
PostPosted: Tue Oct 08, 2013 3:57 am 
Offline

Joined: Sat Mar 05, 2011 6:01 am
Posts: 35
Location: SF Bay Area
not sure why you are having this problem. but what about the idea of a small spacer between the bb shell and the screwed in bearing? that would move the crankset outward just a bit and keep the chain from rubbing on the inside of the derailleur blade. not sure how this would affect shifting, but would definitely move the crankset outward...just a tad. spacers are made that slide on over the bearing threads and right up against the inner face of the bearing.


Top
 Profile  
 
PostPosted: Wed Oct 16, 2013 9:55 pm 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
eflayer wrote:
not sure why you are having this problem. but what about the idea of a small spacer between the bb shell and the screwed in bearing? that would move the crankset outward just a bit and keep the chain from rubbing on the inside of the derailleur blade. not sure how this would affect shifting, but would definitely move the crankset outward...just a tad. spacers are made that slide on over the bearing threads and right up against the inner face of the bearing.


I do have a few unused spacers laying around from MTB Hollowtech bottom brackets that I could use on the driveside, but wouldn't this cause issues with engagement of the left crankarm on my Rotor crankset?

I hate to loose a crankarm mid-ride.


Top
 Profile  
 
PostPosted: Sat Oct 19, 2013 8:47 pm 
Offline

Joined: Fri Apr 13, 2012 7:25 pm
Posts: 87
I lent a dremel today and grinded off the stops on the derailleur. Had to add longer limit screws afterwards and don't think I can remove more material from it. I tried bending the cage a bit too.

From having chain rub in the four largest cassette cogs, I only now have it when riding on the largest cog and small chainring!

I have however contacted Rotor and will ask what their tolerance on bottom bracket widths are and what they say regarding adding a small spacer, 0.5mm or so, to move the crank more outwards.


Top
 Profile  
 
Posted: Sat Oct 19, 2013 8:47 pm 


Top
  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ] 


Who is online

Users browsing this forum: Bing [Bot], em3, ewwhite, Exabot [Bot], Google Adsense [Bot], indywagon, NoInterVention, sfo423, Yahoo [Bot] and 47 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Front derailleur question

in Road

Elrey

9

519

Sun Jan 05, 2014 11:52 am

Elrey View the latest post

There are no new unread posts for this topic. Issue with Di2 Front Derailleur

in Road

AndreLM

5

156

Wed Sep 03, 2014 1:37 am

AndreLM View the latest post

There are no new unread posts for this topic. Ultegra front derailleur - more durable than 105?

in Road

604Yarks

3

346

Tue Apr 08, 2014 3:49 am

commendatore View the latest post

There are no new unread posts for this topic. Hollowgram, chainline and front derailleur

in Road

CrossRob

3

237

Sun Jul 27, 2014 6:22 am

CrossRob View the latest post

There are no new unread posts for this topic. SRAM Rival Front Derailleur Question

in Road

tominator

1

195

Sat Jun 14, 2014 12:15 am

Getter View the latest post


It is currently Wed Sep 03, 2014 2:12 am

All times are UTC + 1 hour




Advertising   –  FAQ   –  Contact   –  Convert   –  About

© Weight Weenies 2000-2013
hosted by starbike.com


How to get rid of these ads? Just register!


Powered by phpBB