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 02-04-12, 08:03 AM   #1
rangerdavid
Senior Member
Thread Starter
 
rangerdavid's Avatar
 
Join Date: Jun 2009
Location: Boone, North Carolina
Bikes: 2009 Cannondale CAAD9-6 2014 Trek Domaine 5.9
Posts: 5,093
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
need help with an adjustment please

when I shift down into my next to largest cog, my chain "hops" several times before finally settling down into the teeth in the cassette. As best I can tell, it only does this hopping on this cog.

how do I fix this? I'm running a shimano tiagra group with dura ace cables. the cassette is an 11-28 cassette. thanks in advance for any suggestion.
rangerdavid is offline   Reply With Quote
Old 02-04-12, 08:32 AM   #2
reptilezs
Senior Member
 
Join Date: Sep 2004
Location: boston, ma
Bikes:
Posts: 2,852
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
hanger alignment, more cable tension, worn cassette/chain. dirty cables usually manifest itself when going to a smaller cog or the relaxed position of the RD.
reptilezs is offline   Reply With Quote
Old 02-04-12, 01:10 PM   #3
tmat
Curmudgeon
 
tmat's Avatar
 
Join Date: Jan 2012
Location: Lost in a maze of cornfields
Bikes: 64cm TREK 2.3, 68.5 cm Schwinn, and 22.5 inch Trek 4500
Posts: 49
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
First try adjusting the barrel on your rear derailler, which will change the inner wire tension. (A little turn goes a long way.)

See the "Checking the Rear Indexing Adjustment" section at Park Tool for the how-to if you're unfamiliar with this adjustment. (You'll need to scroll down a ways to see that section.)
tmat is offline   Reply With Quote
Old 02-04-12, 01:33 PM   #4
rangerdavid
Senior Member
Thread Starter
 
rangerdavid's Avatar
 
Join Date: Jun 2009
Location: Boone, North Carolina
Bikes: 2009 Cannondale CAAD9-6 2014 Trek Domaine 5.9
Posts: 5,093
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
brand new cassette, brand new chain. I'll try the barrell adjustments.... I just had the entire drive train rebuilt, so I'm hoping it's a simple adjustment. thanks, I'll give that a shot
rangerdavid is offline   Reply With Quote
Old 02-04-12, 02:50 PM   #5
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: 29,682
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 230 Post(s)
When erratic shifting occurs only on a single sprocket it's usually difficult to resolve via the adjusting barrel, since that affects all sprockets equally. The erratic shifting you're seeing could be the result of unequal spacing of the one sprocket to it's neighbors, of if it's a loose sprocket cassette, one sprocket turned backward. These issues are rare but of unheard of, and I only suggest them since the cassette is new.

Most likely it's a hanging cable as mentioned by reptilezs. there's a definitive test to verify if this is the case which you should do before anything else.

Shift to the one sprocket larger than the problem shift, then do the problem shift, and stop pedaling if the shift delays or hangs to keep it there. Pluck the bare wire away from the downtube hard like a guitar string, then resume pedaling. Plucking this way pulls down the wire against friction, so if it shifts immediately after plucking then it's dirty, sticky, or worn cables. Repeat the test a few times so verify if it works fairly consistently to confirm the diagnosis.

The other cable related issue could be a fraying inner wire up near the levers, The frayed area will hang where it enters the housing, causing the RD to always stick on the same upshift. This often happens just before the wire snaps, and can therefore be an early warning.
__________________
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 online now   Reply With Quote
Old 02-04-12, 03:28 PM   #6
reptilezs
Senior Member
 
Join Date: Sep 2004
Location: boston, ma
Bikes:
Posts: 2,852
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by FBinNY View Post
The erratic shifting you're seeing could be the result of unequal spacing of the one sprocket to it's neighbors, of if it's a loose sprocket cassette, one sprocket turned backward. These issues are rare but of unheard of, and I only suggest them since the cassette is new.

.
had this happen with a new sram cassette. mid to high level one with an alloy carrier. the first 7 cogs shifted like crap and the biggest 3 were perfect. the alloy carrier was not machined square so the loose cogs were misaligned and off axis with the freehub body/axle. drove me nuts till i realized what was going on
reptilezs is offline   Reply With Quote
Old 02-04-12, 05:00 PM   #7
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: 6,278
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 35 Post(s)
Quote:
Originally Posted by rangerdavid View Post
brand new cassette, brand new chain. I'll try the barrel adjustments.... I just had the entire drive train rebuilt, so I'm hoping it's a simple adjustment. thanks, I'll give that a shot
As noted could be a lot of things and not likely barrel adjustment. Best to return it to whoever did the drive train rebuild.
cny-bikeman is offline   Reply With Quote
Old 02-04-12, 07:35 PM   #8
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Posts: 9,274
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 49 Post(s)
Quote:
Originally Posted by FBinNY View Post
....of if it's a loose sprocket cassette, one sprocket turned backward. These issues are rare but of unheard of, and I only suggest them since the cassette is new. .....
Since the wide spline is offset, how do you turn a sprocket backward?
Bill Kapaun is offline   Reply With Quote
Old 02-04-12, 08:56 PM   #9
spathfinder3408
spathfinder34089
 
spathfinder3408's Avatar
 
Join Date: Jun 2007
Location: Washington State
Bikes: fuji s12s, Schwiin Le Tour, Puegot mtn. bike, Hiawatha crusier
Posts: 200
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
My bike did the same t hing. Took the bike on a trip and was jumping in second to lowest gear. I put it into the lowest gear and looked down to see if derailer was aligned with lowest gear. It was not, so a couple turns of the barrel screw on the derailer and it fixed it. this was an index shifter, so it was critical for alignment of derailer in each gear.
spathfinder3408 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 03:14 PM.