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

Thread Tools Search this Thread
Old 05-13-12, 12:52 PM   #1
Junior Member
Thread Starter
Join Date: Apr 2012
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
chain line problem

the bike: 88 schwinn premis
the drive train: shimano RX100
brief history: i built this bike a while back using rx100 f&r derailleur and crank. in the back i was using a 7 speed cassette that was spaced out on a 9 speed cassette body. i turned the bike into a single speed for a while and now i'm gearing it back up using the same parts as above. the only difference is i'm using a different cassette, still a 7 speed though.

The problem i'm having is my chain line is way off. when i have the front on the small chain wheel, the chain grinds on the big chain wheel. its only straight if i have it in the 4th gear up. iv changed cassettes on plenty of bikes with no problem, i don't understand why i'm having this problem
bearjew is offline   Reply With Quote
Old 05-13-12, 01:05 PM   #2
Senior Member
dsbrantjr's Avatar
Join Date: Sep 2010
Location: Roswell, GA
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Posts: 5,412
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 365 Post(s)
Are you by any chance running a chain which is too wide? Is it possible that you have left an un-needed spacer behind the cassette?
dsbrantjr is offline   Reply With Quote
Old 05-13-12, 01:18 PM   #3
Senior Member
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,438
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
If needed you can easily put a 2 mm bottom bracket spacer between the BB driveside cup and the frame. This will move the crankset out 2 mm.

Changing the cassette should not change the chainline. Perhaps you have not stacked the cogs and spacers the same as before.
Al1943 is offline   Reply With Quote
Old 05-13-12, 01:35 PM   #4
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: 35,300
Mentioned: 105 Post(s)
Tagged: 1 Thread(s)
Quoted: 3644 Post(s)
Start by finding what the actual chainline is. You can do this empirically by measuring from the chainrings to the downtube and adding half the diameter of the tube. Then compare to the standards or to the cassettes chainline (distance from inside of dropout, subtracted from the dropout width).

You can also measure it directly by placing a straightedge (edgewise, not flat) on a secant against the outer chainring, and carrying it back to the cassette, then allowing for the offset to the center of the chainrings seeing where it compares to the center of the cassette.

Based on that, you can decide if you're best option is to move the cranks outboard, check rear triangle centering, increase chainring separation, or use a narrower chain.
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

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 12:09 AM.

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.
  • Ask a Question
    get answers from real people!
Click to start entering your question.