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 10-14-07, 03:40 PM   #1
bluenote157
Senior Member
Thread Starter
 
bluenote157's Avatar
 
Join Date: Apr 2006
Location: Orange County CA
Bikes: Surly CC, Raleigh Team Pro, Specialized Rockhopper with an xtracycle
Posts: 960
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
how do I determine the correct chain length?

I've looked through the Shimano Technical documents and it states the chain should be on the largest chainring and smallest cog in order to determine the length. Next, it mentions that the pulleys should be perpendicular to the ground. What i'm not sure about is if the pulleys and the center of the freewheel all have to line up to perpendicular or is it only the two pulleys that need to line up and be perpendicular?
I have a double setup..105 front, ultegra rear, 9 speed chain...if that makes any difference.
bluenote157 is offline   Reply With Quote
Old 10-14-07, 03:56 PM   #2
FlatFender
Senior Member
 
FlatFender's Avatar
 
Join Date: Aug 2006
Location: Raleigh NC
Bikes:
Posts: 1,015
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
run the chain around the large chainring, and the largest cog (dont run it through the rear derailleur yet)
then add 2 links (some people only add one link, but ONE time I came out with a chain that was too short, so I add two links)
Then seperate the chain there.
Run it through the derailleurs, and you should be good to go.

Last edited by FlatFender; 10-14-07 at 11:51 PM.
FlatFender is offline   Reply With Quote
Old 10-14-07, 09:19 PM   #3
ginsoakedboy
Banned
 
Join Date: Dec 2004
Bikes:
Posts: 616
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by FlatFender View Post
run the chain around the large chainring, and the largest cog (dont run it through the rear derailleur yet)
then add 2 links
Exactly right.
ginsoakedboy is offline   Reply With Quote
Old 10-15-07, 06:36 AM   #4
DougG
Road Runner
 
DougG's Avatar
 
Join Date: Sep 2003
Location: Rochester Hills, MI
Bikes: 2017 Felt VR5, 2012 Specialized Crosstrail
Posts: 1,079
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
The Park Tool site has a good section on this. They recommend the same method as the above two posts, and also have a way to calculate the length using the number of teeth on the largest ring and cog, and the distance from the crank axis to the rear axle.

I'm working on installing a new drivetrain, including the chain of course, so just for fun I'll see how the calculation compares to the fit + 2 method.
DougG is offline   Reply With Quote
Old 10-15-07, 06:53 AM   #5
Zouf
Senior Member
 
Join Date: Aug 2004
Bikes:
Posts: 736
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by FlatFender View Post
run the chain around the large chainring, and the largest cog (dont run it through the rear derailleur yet)
then add 2 links (some people only add one link, but ONE time I came out with a chain that was too short, so I add two links)
Then seperate the chain there.
Run it through the derailleurs, and you should be good to go.
This is the SRAM method. OP refers to Shimano method, which is big+small+vertical. Shimano refers to the pulleys being on top of each other, regardless of where the freewheel happens to be - most probably behind. Both methods will lead to different chain lenghts, depending on largest cog in back (Shimano method does not take the size of largest cog into account). I prefer the SRAM method (big+big+2) since it addresses the one limitation of chain length: being able to accomodate the most extreme situation, i.e. big+big.
Zouf is offline   Reply With Quote
Old 10-15-07, 07:51 AM   #6
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)
http://www.bikeforums.net/search.php?do=process
Portis is offline   Reply With Quote
Old 10-15-07, 08:07 AM   #7
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: 29,112
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 175 Post(s)
Quote:
Originally Posted by Zouf View Post
I prefer the SRAM method (big+big+2) since it addresses the one limitation of chain length: being able to accomodate the most extreme situation, i.e. big+big.
Exactly and this is a critical fit issue. We all know you shouldn't ride in big-big but one time at least, due to brain-fade or needing a lower gear in a rush, you will wind up in that combination. The chain must allow it or the resulting damage will be quite impressive.

The Shimano method works but assumes you are within their published tooth differences and total teeth ranges for the rear derailleur, chainrings and cassette. If you take any liberties with these recommendations, the chain maybe too short.
HillRider is offline   Reply With Quote
Old 10-15-07, 08:16 AM   #8
BigBlueToe
Senior Member
 
BigBlueToe's Avatar
 
Join Date: Aug 2006
Location: Central Coast, CA
Bikes: Surly LHT, Specialized Rockhopper, Nashbar Touring (old), Specialized Stumpjumper (older), Nishiki Tourer (model unknown)
Posts: 3,393
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I used Sheldon Brown's article in combination with the Park site. One thing I found - chain links either have the metal faces on the outside or the inside. (I'm not sure if I've got my terminology straight, but look at a chain and, hopefully, you'll see what I'm talking about.) An "outer link" has to connect to an "inner link". Therefore, sometimes you might have to add or subtract a link to your "perfect length" to make this come out right. All I know is that I installed two chains this summer using these sites, and both bikes work fine. It wasn't that tough.
BigBlueToe is offline   Reply With Quote
Old 10-15-07, 08:40 AM   #9
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: 29,112
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 175 Post(s)
Quote:
Originally Posted by BigBlueToe View Post
Therefore, sometimes you might have to add or subtract a link to your "perfect length" to make this come out right.
When faced with this problem, use the the longer configuration.
HillRider is offline   Reply With Quote
Old 10-15-07, 09:17 AM   #10
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)
Quote:
Originally Posted by bluenote157 View Post
Next, it mentions that the pulleys should be perpendicular to the ground. What i'm not sure about is if the pulleys and the center of the freewheel all have to line up to perpendicular or is it only the two pulleys that need to line up and be perpendicular?
It has nothing to do with the freewheel center. It means that a line through the two pulley wheels is at a right angle to the ground. The dérailleur pivot spring will locate the RD however it sees fit, and that won't change the measurement.

IMO the Shimano method is at least as good as the "big-big" method, but isn't as easy to use perform.
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers
DMF is offline   Reply With Quote
Old 10-15-07, 09:21 AM   #11
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)
Quote:
Originally Posted by HillRider View Post
The Shimano method works but assumes you are within their published tooth differences and total teeth ranges for the rear derailleur, chainrings and cassette. If you take any liberties with these recommendations, the chain maybe too short.
Conversely, it may be too long. No method can accommodate a wrongly sized dérailleur. The Shimano method at least centers the arm range to minimize the effects at either end.
__________________
Stupidity got us into this mess - why can't it get us out?

- Will Rogers
DMF is offline   Reply With Quote
Old 10-15-07, 09:57 AM   #12
bluenote157
Senior Member
Thread Starter
 
bluenote157's Avatar
 
Join Date: Apr 2006
Location: Orange County CA
Bikes: Surly CC, Raleigh Team Pro, Specialized Rockhopper with an xtracycle
Posts: 960
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
thanks to all that replied. I ended up going the shimano perpendicular method. All is well...so far..

..now about this b-setting thing???....
bluenote157 is offline   Reply With Quote
Old 10-15-07, 10:46 AM   #13
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: 29,112
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 175 Post(s)
Quote:
Originally Posted by DMF View Post
Conversely, it may be too long. No method can accommodate a wrongly sized dérailleur. The Shimano method at least centers the arm range to minimize the effects at either end.
Too long a chain is only a nuisance and keeps you from effectively using the small-small combinations. If you do inadvertently use small-small no harm is done, the chain just hangs loose.

Too short can lead to catastrophic damage so if there has to be a choice, other than perfect, go with too long.

BTW, big-big+2 will give you the proper chain length if you are within the recommended tooth count for your rear derailleur and will allow you to use small-small without the chain going completely slack.
HillRider 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 07:45 PM.