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 12-28-10, 07:33 PM   #1
GRedner
Senior Member
Thread Starter
 
Join Date: Aug 2006
Location: Brookline, MA
Bikes:
Posts: 514
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Time for: What's Wrong With My Derailleur!

Hi all,

I was changing a tire tonight, and I think I may have done something bad to my rear derailleur. I had the wheel partway back on, and I realized I hadn't shifted into the smallest cog, so I tried to do so. The derailleur didn't move, so I tried shifting to a bigger cog instead of a smaller one. The shift lever gave some resistance when I tried to go that way, so (here comes the Bad Move) I kinda forced it. A couple of times. Nothing bad seemed to happen, so I finished putting the wheel on.

I was testing the shifting afterwards, and things were quite messed up. I couldn't reach the smallest cogs, nor could I reach the largest. The shifter clicks, and pays out or pulls in cable for each shift, but the derailleur does not move as it should. Towards the smaller cogs, the cable goes completely slack, yet the derailleur does not move any further outward. Towards the larger ones, the cable is taut, but I still cannot shift into the largest cog unless I pull on the cable by hand to increase the tension even more.

I've tried playing around with the cable tension adjustment, but the result is that I can make the biggest cogs accessible by increasing tension, but no amount of loosening will let me reach the smallest ones.

So: what's my next step? Is there something I could have overtightened and stripped or bent when I forced the downshift? What should I look for?

The bike is a Specialized Sirrus, the rear derailleur is Sora, with trigger shifters.
GRedner is offline   Reply With Quote
Old 12-28-10, 07:45 PM   #2
dddd
Ride, Wrench, Swap, Race
 
dddd's Avatar
 
Join Date: Jan 2010
Location: Northern California
Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Posts: 5,069
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
It sounds like the rear derailer housing, having been heavily compressed, may have pulled thru a ferrule a bit, impeding the smooth movement of the inner wire.

Another possibility is that a single strand or two of the inner wire broke, partially unravering within the housing and similarly impeding smooth cable movement. Broken strands inside the shifter are most common and would require a bit of care to extract the cable's end.

I would start by removing the cable anchor bolt and sliding the rear-most cable housing off of the cable, then test that the shifting movements are actuating the cable through the front-most cable housing and around the bottom bracket guide.
Use care to keep the end of the wire from fraying about, this will make reassembly easier.

A new spare inner cable wire and a length of the rear-most cable housing (plus ferrules) are really good items to have around as spares.

All praise be to Allah, your cable's onset of failure occurs when the bike is in your workshop instead of out on the road.

Last edited by dddd; 12-28-10 at 08:45 PM. Reason: noted "spares"
dddd is offline   Reply With Quote
Old 12-28-10, 08:18 PM   #3
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 8,065
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Quote:
Originally Posted by GRedner View Post
Hi all,

I was changing a tire tonight, and I think I may have done something bad to my rear derailleur. I had the wheel partway back on, and I realized I hadn't shifted into the smallest cog, so I tried to do so. The derailleur didn't move, so I tried shifting to a bigger cog instead of a smaller one. The shift lever gave some resistance when I tried to go that way, so (here comes the Bad Move) I kinda forced it. A couple of times. Nothing bad seemed to happen, so I finished putting the wheel on.
I, too, would carefully examine the cable and housing. I'm guessing you crimped something when you were installing the wheel. You might end up taking it to a shop and asking them- sometimes it takes an expert eye to spot what's wrong.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline   Reply With Quote
Old 12-28-10, 08:48 PM   #4
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 22,149
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 1131 Post(s)
Did you take the wheel back out , shift back and forth and see if it works
without the wheel in, just going in and out?
then, put the wheel back in , put it in a repair stand ,
[or hang from a cord so you can work the drivetrain with the wheel off the ground]
and shift it back and forth while turning the pedals etc..?
fietsbob is offline   Reply With Quote
Old 12-28-10, 08:53 PM   #5
operator
cab horn
 
Join Date: Jun 2004
Location: Toronto
Bikes: 1987 Bianchi Campione
Posts: 28,306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Check to see if the chain is sitting off the upper pulley...
operator is offline   Reply With Quote
Old 12-28-10, 08:55 PM   #6
dddd
Ride, Wrench, Swap, Race
 
dddd's Avatar
 
Join Date: Jan 2010
Location: Northern California
Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Posts: 5,069
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Quote:
Originally Posted by fietsbob View Post
Did you take the wheel back out , shift back and forth and see if it works
without the wheel in, just going in and out?
then, put the wheel back in , put it in a repair stand ,
[or hang from a cord so you can work the drivetrain with the wheel off the ground]
and shift it back and forth while turning the pedals etc..?
Good thinking, and remionds me of how sometimes the rear cable housing gets hung up on certain quick-release nuts or a rack strut, either of which can somewhat foul the shifting. The housing should follow it's own path and not tucked in or stuffed under, etc.
dddd is offline   Reply With Quote
Old 12-29-10, 08:12 AM   #7
GRedner
Senior Member
Thread Starter
 
Join Date: Aug 2006
Location: Brookline, MA
Bikes:
Posts: 514
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks everyone for the advice!

I took out the wheel and unclamped the shifter cable from the derailleur, and quickly found the problem. The cable was not sliding freely through the last piece of housing, either when pulled by the shifter or by hand. Looking more closely at the housing, I can see a spot where it looks like it buckled under the compression, and when I try to pull the cable through by hand, it grinds at that spot.

Looks like I have a nice walk to the shop ahead of me this morning!

Quote:
All praise be to Allah, your cable's onset of failure occurs when the bike is in your workshop instead of out on the road.
Yes indeed! Thanks again.
GRedner is offline   Reply With Quote
Old 12-29-10, 08:42 AM   #8
cny-bikeman
Mechanic/Tourist
 
Join Date: Apr 2007
Location: Syracuse, NY
Bikes: 2008 Novara Randonee - love it. Would have more bikes if I had time to ride them all. Previous bikes: 1968 Motobecane Mirage, 1972 Moto Grand Jubilee (my fav), Jackson Rake 16, 1983 C'dale ST500.
Posts: 6,430
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 97 Post(s)
Ah, yes - mechanic's number one rule when things don't go right:

STOP
OBSERVE
THINK
REDO
then and only then
WHACK IT HARDER
cny-bikeman is offline   Reply With Quote
Old 12-29-10, 06:26 PM   #9
dddd
Ride, Wrench, Swap, Race
 
dddd's Avatar
 
Join Date: Jan 2010
Location: Northern California
Bikes: Cheltenham-Pederson racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Posts: 5,069
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Great.
And if you haven't done the install yet, and are re-using the inner wire, please cut the new housing a quarter inch shorter than the old one.
This way, the previously-clamped (and damaged to a degree) spot on the inner wire will be pulled past the binder bolt washer and not be subject to normal cyclic tension in use that might likely lead to a fractured strand.
dddd is offline   Reply With Quote
Old 12-29-10, 07:04 PM   #10
Jeff Wills
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Bikes:
Posts: 8,065
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 75 Post(s)
Quote:
Originally Posted by cny-bikeman View Post
Ah, yes - mechanic's number one rule when things don't go right:

STOP
OBSERVE
THINK
REDO
then and only then
WHACK IT HARDER
And if that doesn't work: Get A Bigger Hammer.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline   Reply With Quote
Old 12-29-10, 10:51 PM   #11
GRedner
Senior Member
Thread Starter
 
Join Date: Aug 2006
Location: Brookline, MA
Bikes:
Posts: 514
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by dddd View Post
And if you haven't done the install yet, and are re-using the inner wire, please cut the new housing a quarter inch shorter than the old one.
This way, the previously-clamped (and damaged to a degree) spot on the inner wire will be pulled past the binder bolt washer and not be subject to normal cyclic tension in use that might likely lead to a fractured strand.
Thanks for the tip! In the end I had the shop do the work, and they replaced both the housing and the shifter cable, which was rusty in several spots and probably overdue for replacement anyhow. Now it shifts silky-smooth
GRedner is offline   Reply With Quote
Old 12-29-10, 11:10 PM   #12
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 30,849
Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 873 Post(s)
Quote:
Originally Posted by GRedner View Post
Looks like I have a nice walk to the shop ahead of me this morning!
Why walk? You might not be able to shift effectively, but if it's in a mid range gear you can ride it as a single speed.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY 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 03:08 PM.