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 12-01-06, 02:41 PM   #1
BikeManDan
Senior Member
Thread Starter
 
BikeManDan's Avatar
 
Join Date: Jul 2006
Location: Oakland, CA
Bikes:
Posts: 1,300
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
smooth downshifts but sloppy upshifts

I'm still a learning bike mechanic (obviously from this question)


SRAM 8spd cassette + Shimano XT short cage derailleur + Shimano Alivio shifters

I can adjust the derailleur to get near perfect downshifts but then the upshifts go to sh^t. The chain stays on the last sprocket and doesnt shift over as if theres not enough movement from the derailleur to froce the chain off to the next. Isn't that an operation of the shfiter itself? (it pulls the cable some specified amount)

What oversight am I making here?
BikeManDan is offline   Reply With Quote
Old 12-01-06, 03:02 PM   #2
Steev
Senior Member
 
Steev's Avatar
 
Join Date: Jul 2005
Location: Backwoods of Ontario
Bikes:
Posts: 2,150
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You may well have a problem with gunked up or corroded shift cable. Less likely but possible is the derailler pivots needing lube or the derailler needing a good cleaning .
Steev is offline   Reply With Quote
Old 12-01-06, 03:22 PM   #3
AndrewP
Senior Member
 
Join Date: Sep 2001
Location: Montreal
Bikes: Peugeot Hybrid, Minelli Hybrid
Posts: 6,521
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
For the upshifts, the spring in the derailler pulls it into position, and the cable only stops it moving too far. Therefore it is probably just gunk in the cable housing or in the shifter that is slowing the movement. Cleaning the shifter mechanism with WD-40 is the first thing to do. If that isnt enough remove the cables from their housing and clean them out.
AndrewP is offline   Reply With Quote
Old 12-01-06, 04:30 PM   #4
waterrockets 
Making a kilometer blurry
 
waterrockets's Avatar
 
Join Date: May 2006
Location: Austin (near TX)
Bikes: rkwaki's porn collection
Posts: 26,130
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
One quick check is to make sure your der cable is not too tight. If you rotate the der barrel 1/4 turn clockwise, does that make it better?

I agree with the others that it's more likely to be old or guncked-up housing and cables, but the barrel adjuster is so easy to try. If you take the rear wheel out, does it still move the der slowly to the right? If so, go for the cables/housing.
waterrockets is offline   Reply With Quote
Old 12-01-06, 05:06 PM   #5
BikeManDan
Senior Member
Thread Starter
 
BikeManDan's Avatar
 
Join Date: Jul 2006
Location: Oakland, CA
Bikes:
Posts: 1,300
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The bike has had very light use and the cables are in good condition

I just went out and greased the cable and housings. No real improvement

The major problem is the 5->4 shift. This one always gets hung up
BikeManDan is offline   Reply With Quote
Old 12-01-06, 05:26 PM   #6
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)
Quote:
Originally Posted by dwoloz

The major problem is the 5->4 shift. This one always gets hung up
5 to 4 sounds like an upshift, smaller cog to a larger cog, no?

Al
Al1943 is offline   Reply With Quote
Old 12-01-06, 10:26 PM   #7
BikeManDan
Senior Member
Thread Starter
 
BikeManDan's Avatar
 
Join Date: Jul 2006
Location: Oakland, CA
Bikes:
Posts: 1,300
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Err well I sometimes get confused about upshift versus downshift


I'm talking about bigger cog going to smaller cog
Going from small to large is no problem, it shifts smooth as butter. Going back down is where it gets hung up
BikeManDan is offline   Reply With Quote
Old 12-02-06, 07:47 AM   #8
waterrockets 
Making a kilometer blurry
 
waterrockets's Avatar
 
Join Date: May 2006
Location: Austin (near TX)
Bikes: rkwaki's porn collection
Posts: 26,130
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by dwoloz
Err well I sometimes get confused about upshift versus downshift


I'm talking about bigger cog going to smaller cog
Going from small to large is no problem, it shifts smooth as butter. Going back down is where it gets hung up
You didn't answer my questions above. Is it slow moving when the wheel is removed? This will tell us if there's something slowing it down, or if it's a mechanical adjustment issue.
waterrockets is offline   Reply With Quote
Old 12-04-06, 09:56 AM   #9
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)
Quote:
Originally Posted by dwoloz
Err well I sometimes get confused about upshift versus downshift


I'm talking about bigger cog going to smaller cog
Going from small to large is no problem, it shifts smooth as butter. Going back down is where it gets hung up
That's an upshift.

This is often an indication of excess friction due to a dirty and/or corroded shift cable and cable housing. With STI shifters it's best to replace both shift cables and cable housings on a fairly regular basis. The short housing just before the rear derailleur is the most critical.
Also flushing out the shifters with WD40 may help.

Al
Al1943 is offline   Reply With Quote
Old 12-05-06, 12:27 AM   #10
Cadfael
Senior Member
 
Cadfael's Avatar
 
Join Date: Nov 2006
Location: United Kingdom
Bikes:
Posts: 475
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Don't shoot me here if I am talking crazy...

But on some deraillers I have seen an adjustment screw that changes the distance of the top wheel on the cage to the cogs on the backwheel... could this make a difference? It just seems to my (often muddy) way of thinking that is the distance is set to far the chain will bend with the deraillier (as they are designed to do I suppose) rather than move with it.
Cadfael 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 07:28 AM.