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 01-29-06, 12:36 PM   #1
The Great Stonk
Senior Member
Thread Starter
 
Join Date: Dec 2005
Bikes:
Posts: 203
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
ghost shifting problems

im looking for a few words of advice, or a solution to a problem thats still eluding me. - new bike, as of yet unridden out of the workshop, with a nasty ghost shift under load.

frame - kinesis maxlight (easton ultra light) 18"
cranks - xt hollowtech II
chain - sram 99 hollowpin (no split link, chain is hard joined)
cassette - sram pg980 11-32
mech and shifters are sram x7

ive been working with bikes for a number of years now, put ive never had such trouble...

the chainline is set central (middle ring + 5th sproket produces straight chain line) ive removed the split link, ive tried a few different chain line spacings on the BB, rd is adjusted perfectly with brand spaking new clarks preium cables.

under load (load considerd to be hard in saddle acceleration, or climbing in the saddle) the chain will jump up the cassette onto a larger sproket, it does this in all 3 front rings, producing a potential face + stem smash.

the frame is a very lightweight (1600g ish) ride, it has got a fair amount of flex in it, but not so much to lengthen the gear cable run enough to cause an upshift.

now can anyone here think of anything ive missed out in hunting for the problem ? or have any other ideas how im going to sort out my new steed ?
The Great Stonk is offline   Reply With Quote
Old 01-29-06, 12:49 PM   #2
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 29,121
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 180 Post(s)
Ghost shifting is usually associated with a flexy frame with a weak rear triangle. The off-center pull of the chain flexes the rear triangle to the right and pulls the chain off of the cog it's on. Usually the ghost shift is to a smaller cog so what you report is unusual. I don't think its a cable problem though.
HillRider is offline   Reply With Quote
Old 01-29-06, 02:15 PM   #3
The Great Stonk
Senior Member
Thread Starter
 
Join Date: Dec 2005
Bikes:
Posts: 203
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
i know for a fact the mech and cage are fine, since they are from my last bike - ill look into the hanger next chance i get (wednesday)
The Great Stonk is offline   Reply With Quote
Old 01-29-06, 02:28 PM   #4
wagathon
Banned
 
wagathon's Avatar
 
Join Date: Apr 2005
Bikes:
Posts: 1,727
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are the cogs warn, e.g., instead of U-shaped, does one side have more slope?
wagathon is offline   Reply With Quote
Old 01-29-06, 04:04 PM   #5
The Great Stonk
Senior Member
Thread Starter
 
Join Date: Dec 2005
Bikes:
Posts: 203
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by wagathon
Are the cogs warn, e.g., instead of U-shaped, does one side have more slope?
the cassette is next to brand new, were talking less then 10 miles.
The Great Stonk is offline   Reply With Quote
Old 01-29-06, 10:14 PM   #6
wagathon
Banned
 
wagathon's Avatar
 
Join Date: Apr 2005
Bikes:
Posts: 1,727
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by The Great Stonk
the cassette is next to brand new, were talking less then 10 miles.
Then, are you using the same old chain? If so, many miles on it?
wagathon is offline   Reply With Quote
Old 01-29-06, 10:16 PM   #7
georgiaboy
Retro-nerd
 
georgiaboy's Avatar
 
Join Date: Mar 2005
Location: Morningside - Atlanta
Bikes: 1991 Serotta Colorado II, 1986 Vitus 979, 1971 Juene Classic, 2008 Surly Crosscheck, 1949 Riva Sport
Posts: 1,583
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
right, the chain being stretched could be the cause of this problem
__________________
Would you like a dream with that?
georgiaboy is offline   Reply With Quote
Old 01-29-06, 10:17 PM   #8
Ronin
fitter, happier
 
Ronin's Avatar
 
Join Date: Dec 2005
Location: Lawrence
Bikes: I have more bikes than fingers. So I can't count em
Posts: 200
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by HillRider
Ghost shifting is usually associated with a flexy frame with a weak rear triangle. The off-center pull of the chain flexes the rear triangle to the right and pulls the chain off of the cog it's on. Usually the ghost shift is to a smaller cog so what you report is unusual. I don't think its a cable problem though.
Plus one. I'm guessing your rear cable runs under the BB? Frame flex causing the cable to tug. Look at the cable guide and provide the slickest lube you can find.
Ronin is offline   Reply With Quote
Old 01-30-06, 12:12 AM   #9
Chongo
Senior Member
 
Chongo's Avatar
 
Join Date: Nov 2004
Bikes: Russ Denny custom
Posts: 233
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Don't forget to check your rear derallieur hanger alignment.
Chongo is offline   Reply With Quote
Old 01-30-06, 06:20 PM   #10
The Great Stonk
Senior Member
Thread Starter
 
Join Date: Dec 2005
Bikes:
Posts: 203
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
chain is also new im afraid, cable run is along the top tube too...

cant check the dropout hangar untill weds im afraid, ill give yall an update when i do.
The Great Stonk is offline   Reply With Quote
Old 02-01-06, 08:07 AM   #11
The Great Stonk
Senior Member
Thread Starter
 
Join Date: Dec 2005
Bikes:
Posts: 203
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
success!

the hangar was slightly twisted (barly noticable to the eye, but the apropriate toolage revealed it) bent it back, and orderd 2 spares for the future, and it seems no amount of practice gate starts will make it jump out of gear

cheers fellas, ill see about getting a few pics of my new steed up
The Great Stonk 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 06:07 AM.