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 04-30-07, 07:58 PM   #1
EXW
Junior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Front Derailluer Help

OK, this is kind of an odd one

I cannot shift into the small chainring on my mountain bike. The front derailluer is XT and haven't had any problems with it in the past. When I try to shift into the small ring, the derailluer doesn't move over enough. I thought it was an issue with the limit screws, but when I had it in the stand I noticed that the derailluer itself is hitting the seat tube.

Basically, if I'm in the middle chainring and I shift into the smaller one, the derailluer moves, but is stopped by the seat tube before it can move over enough to shift the chain.

Any help is appreciated.

Thanks
EXW is offline   Reply With Quote
Old 04-30-07, 08:31 PM   #2
goldbam
Wanna race?
 
goldbam's Avatar
 
Join Date: Jan 2005
Location: Edmonds, Wa
Bikes:
Posts: 224
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
First off, have you ever been able to shift into the lowest chain ring? Other than that, the derailluer must be able to shift it over. Make sure it is positioned about .5mm higher than the largest chain ring and that it is also angled correctly.
__________________
2006 Flyte SRS-2
2004 Fuji Finest
2002 Raleigh M-60
goldbam is offline   Reply With Quote
Old 04-30-07, 08:50 PM   #3
Portis
Banned.
 
Join Date: Sep 2003
Location: Home alone
Bikes: Trek 4300 X 2. Trek 1000, Trek 6000
Posts: 6,019
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
This doesn't make sense. If the derailleur is resting on the seat tube and it used to work alright before than the only logical possibility is that the small ring moved inward for some reason. Not sure how this can happen without changing BB spindle and or crankset.
Portis is offline   Reply With Quote
Old 04-30-07, 09:05 PM   #4
EXW
Junior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks for the replies. I agree that it doesn't make sense.

My original thought was that the angle was off but it appears to be straight. I've had this setup for 5 years and shifting into the small chain ring hasn't been a problem before. This weekend was the first time I tried shifting to the small ring this season and that is when I discovered the problem. The derailluer can clear the big chain ring but is then stopped by the seatube before it can fully move the chain (the chain ends up rubbing against it).
EXW is offline   Reply With Quote
Old 05-01-07, 08:32 AM   #5
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It may be excess friction in the shift cable or in the shifter. Check the routing of the cable looking for any interference or kinks. Try cleaning the shifter with WD40.
You may need new cables and cable housings.

Al
Al1943 is offline   Reply With Quote
Old 05-01-07, 08:42 AM   #6
cmdr
Don't call me sir
 
cmdr's Avatar
 
Join Date: Jun 2006
Location: Charlottesville, VA
Bikes: 1954 Holdsworth 3 speed, 1969 Bob Jackson, 1988 Miyata Twelve Hundred (retired), 1989 Schwinn Paramount, 2004 Santa Cruz Blur Classic, 2012 Specialized P3, 2013 Specialized Roubaix Expert Disc
Posts: 615
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
pictures please.
cmdr is offline   Reply With Quote
Old 05-01-07, 08:55 AM   #7
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 17,971
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 172 Post(s)
Quote:
Originally Posted by EXW
Thanks for the replies. I agree that it doesn't make sense.

My original thought was that the angle was off but it appears to be straight. I've had this setup for 5 years and shifting into the small chain ring hasn't been a problem before. This weekend was the first time I tried shifting to the small ring this season and that is when I discovered the problem. The derailluer can clear the big chain ring but is then stopped by the seatube before it can fully move the chain (the chain ends up rubbing against it).
It sounds like your front derailer has moved. Are the derailer plates nearly parallel with the chainring teeth? If not, you've probably twisted around the seat tube a little. Alternatively, did you have a bad shift or crash? Dropped something on the bike? Perhaps the derailer has been bent. Overall, if I'm understanding correctly, your front derailer shouldn't even come close to hitting the seat tube, so it sounds like an alignment problem.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is online now   Reply With Quote
Old 05-01-07, 08:56 AM   #8
JustBrowsing
Señor Miembro
 
JustBrowsing's Avatar
 
Join Date: Mar 2007
Location: DC
Bikes:
Posts: 603
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'm as baffled as everyone else--mainly because the description doesn't seem to make sense. I'd go with Al1943's suggestion to check the cables. Also, try grabbing hold of the exposed cable on the downtube and giving it a few good tugs to make sure the derailleur is moving freely. Also, it sounds like the FD may have slipped so it's not angled correctly (explaining why it's hitting the seat tube), but you mentioned that the angle is okay. At this point I think pics are in order...
JustBrowsing is offline   Reply With Quote
Old 05-01-07, 09:39 AM   #9
DMF 
Elitist Troglodyte
 
DMF's Avatar
 
Join Date: Jun 2006
Location: Dallas
Bikes: 03 Raleigh Professional (steel)
Posts: 6,924
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Possibilities:

1) cable adjustment
2) bent dérailleur
3) incorrect chainline
DMF is offline   Reply With Quote
Old 05-01-07, 04:55 PM   #10
Portis
Banned.
 
Join Date: Sep 2003
Location: Home alone
Bikes: Trek 4300 X 2. Trek 1000, Trek 6000
Posts: 6,019
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
One of my Trek 4300's came stock with the front der. resting on the seat tube. The cause was somehow they put the wrong BB in the bike.
Portis is offline   Reply With Quote
Old 05-01-07, 05:33 PM   #11
I_bRAD
Call me The Breeze
 
I_bRAD's Avatar
 
Join Date: Aug 2006
Location: Corbyville Ontario
Bikes: 2004 Litespeed Siena, 1996 Litespeed Obed, 1992 Miele (unknown model), 1982 Meile Uno LS.
Posts: 3,699
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by goldbam
and that it is also angled correctly.
Quote:
Originally Posted by cyccommute
It sounds like your front derailer has moved. Are the derailer plates nearly parallel with the chainring teeth? If not, you've probably twisted around the seat tube a little.
Quote:
Originally Posted by JustBrowsing
Also, it sounds like the FD may have slipped so it's not angled correctly (explaining why it's hitting the seat tube)
Shall I +1 or is this enough?
I_bRAD is offline   Reply With Quote
Old 05-01-07, 06:22 PM   #12
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Which part of the derailleur hits the seat tube? I didn't pick up on this before.
Al1943 is offline   Reply With Quote
Old 05-01-07, 07:30 PM   #13
EXW
Junior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
First off, thanks to everyone for all of the replies. It is great that to have this many people helping out. Now, I just hope it doesn't turn out to be something stupid.

I took a few pictures that (not the best, sorry). One shows the derailluer in the middle chain ring position and another shows it in the small chain ring.

The derailluer doesn't look like it slipped (the middle and big rings shift fine) and in any case it doesn't look like that would cause it to hit the frame.

Anyway, please keeping the ideas coming. It is probably something simple but I can't figure it out.

Thanks
Attached Images
File Type: jpg bike1.jpg (57.0 KB, 20 views)
File Type: jpg bike2.jpg (43.3 KB, 20 views)
File Type: jpg bike3.jpg (35.4 KB, 22 views)
File Type: jpg bike4.jpg (59.1 KB, 16 views)
EXW is offline   Reply With Quote
Old 05-01-07, 07:45 PM   #14
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: 6,277
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 35 Post(s)
In my opinion the derailleur could go down a bit. I know it worked before, but perhaps the pivots have developed play. Also check the inside of the outer cage for wear. A chain can rub its way right through the cage eventually, and if it has worn it at all it could compromise shifting. You can always cheat and bend the rear part in a bit. Usually does not affect other gears as the lower part is usually not in play when riding typical gears.
cny-bikeman is offline   Reply With Quote
Old 05-01-07, 07:56 PM   #15
JunkYardBike
Since 1938...
 
JunkYardBike's Avatar
 
Join Date: Aug 2006
Location: Northwestern NJ
Bikes:
Posts: 6,208
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by cny-bikeman
In my opinion the derailleur could go down a bit. I know it worked before, but perhaps the pivots have developed play. Also check the inside of the outer cage for wear. A chain can rub its way right through the cage eventually, and if it has worn it at all it could compromise shifting. You can always cheat and bend the rear part in a bit. Usually does not affect other gears as the lower part is usually not in play when riding typical gears.
+1

I assume it's touching your seat tube now because you let out the low limit screw, but the shifting problem is due to drivetrain wear.
JunkYardBike is offline   Reply With Quote
Old 05-01-07, 08:43 PM   #16
Portis
Banned.
 
Join Date: Sep 2003
Location: Home alone
Bikes: Trek 4300 X 2. Trek 1000, Trek 6000
Posts: 6,019
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Regardless of what it "used to do", I think you have a bottom bracket spindle in that bike that is of the wrong length. That is probably one of the main factors here. I also agree that you can probably drop the derailleur height and get it to fall, but I am still convinced that your BB spindle length is not appropriate for that crankset.

Another thing I wonder about is about that derailleur. I wonder if it was designed for the tooth difference you have between the large and small ring. YOu have a 46 and probably a 22 or something to that effect. That would mean it would have to accomodate a 24 tooth difference.

What is the story with the crankset and the derailleur? Are they original?
Portis is offline   Reply With Quote
Old 05-01-07, 09:07 PM   #17
EXW
Junior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It is touching because I let the lower limit out. It hits the seat tube before it can move the chain. I also moved the derailluer down a bit but it didn't help with this problem.

I will check the bottom bracket spindle. The derailluer and the crankset came with the bike, which was built up by the bike store where I bought it (about 6 years ago).

Since checking the spindle is beyond my wrenching skills, I will take it to the lbs.

Thanks for the help everyone. I will report back on what it turns out to be.
EXW is offline   Reply With Quote
Old 05-02-07, 06:09 AM   #18
I_bRAD
Call me The Breeze
 
I_bRAD's Avatar
 
Join Date: Aug 2006
Location: Corbyville Ontario
Bikes: 2004 Litespeed Siena, 1996 Litespeed Obed, 1992 Miele (unknown model), 1982 Meile Uno LS.
Posts: 3,699
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Did you try changing the angle? It's one bolt. Try it. Turn it so the back end comes out a couple degrees.
I_bRAD is offline   Reply With Quote
Old 05-02-07, 01:52 PM   #19
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
Posts: 17,971
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 172 Post(s)
Quote:
Originally Posted by EXW
It is touching because I let the lower limit out. It hits the seat tube before it can move the chain. I also moved the derailluer down a bit but it didn't help with this problem.

I will check the bottom bracket spindle. The derailluer and the crankset came with the bike, which was built up by the bike store where I bought it (about 6 years ago).

Since checking the spindle is beyond my wrenching skills, I will take it to the lbs.

Thanks for the help everyone. I will report back on what it turns out to be.
Looking at your pictures everything looks correct. Could you have some debris in behind the derailer that isn't letting it move over far enough. The thing that has everyone flummoxed is the hitting the seat tube comment. That just should happen unless something was changed.

Another idea is to lube the pivots on the derailer and work them a bit. If things are dirty, it might hang up the shifting.
__________________
Stuart Black
New! Pokin' around the Poconos A cold ride around Lake Erie
New! Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
An Good Ol' Fashion Appalachian Butt Whoopin'.
cyccommute is online now   Reply With Quote
Old 05-02-07, 07:55 PM   #20
EXW
Junior Member
Thread Starter
 
Join Date: May 2006
Bikes:
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OK, took it to the local bike shop and after some initial head scratching, they fixed it. It appears, that the spindle length, front derailluer, and seat tube size have a very low tolerance when put together. I haven't had to adjust the front derailluer on this bike before, so I never realized just how little margin there was in the setup.

In fact, when it was in the work stand and correctly adjusted, it still didn't shift into the small chain ring. However, the mechanic said that once I got on the bike and loaded the rear shock, it would shift fine. So, we took it off the stand and I rode it around the parking lot and sure enough, it shifted perfectly. I would never have guessed this when I had it in the stand at home.

I recently got my shock Push'd and last weekend, when I noticed the problem was the first ride with the tuned shock. I'm wondering if there was enough difference in the shock pre-load to affect this. Just guessing, since this is beyond my level of expertise on the drive chain.

Thanks to everyone for offering suggestions, I really appreciate it.
EXW 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 09:24 AM.