Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Chain Length question

Notices
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.

Chain Length question

Old 08-30-11, 09:52 PM
  #1  
Member
Thread Starter
 
1slowride's Avatar
 
Join Date: Aug 2011
Posts: 33
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Chain Length question

I know I can plug the numbers into an on line calculator but I like to know the formulas.
So it appears to me half of the largest front ring tooth count + half of the largest rear sprocket + two times the crank to rear axle length in inchs gives you the min chain length. I assume the angle distance of the chain between front to back doesnt really amount to enough to worry about. How much do you add to that for the bends around the derailleur wheels and to keep the derailer from being pulled up parallel to the chain in the large front and back combination?

One more question, look at Park tools site, Repair and help section under Chain length sizing
In their example they say the chain for a 32 rear , 42 front with 16.375" axle to crank should be 52", I am thinking more like 69. Is it wrong?
1slowride is offline  
Old 08-30-11, 10:03 PM
  #2  
Senior Member
 
Drew Eckhardt's Avatar
 
Join Date: Apr 2010
Location: Mountain View, CA USA and Golden, CO USA
Posts: 6,341

Bikes: 97 Litespeed, 50-39-30x13-26 10 cogs, Campagnolo Ultrashift, retroreflective rims on SON28/PowerTap hubs

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 550 Post(s)
Liked 325 Times in 226 Posts
For normal bikes forget about measuring. Just wrap the chain around the big ring and big cog without going through the derailleur and cut the chain one full link (inner and outer half-links) past the first point where the two ends could be joined.
Drew Eckhardt is offline  
Old 08-30-11, 10:13 PM
  #3  
I bike in the nude
 
BikeMech's Avatar
 
Join Date: Aug 2009
Location: Mobile,Alabama
Posts: 245

Bikes: Custom. '02 trek 1000 with ultegra and dura ace components. Too much to list... Just ask me

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Or put it in small/small and set the chain so it just clears the rear derailleur and doesn't rub. Either way works but that's how my boss does it and i find it easier than big/big
BikeMech is offline  
Old 08-30-11, 11:01 PM
  #4  
Senior Member
 
Join Date: Jun 2010
Location: Pearland, Texas
Posts: 7,579

Bikes: Cannondale, Trek, Raleigh, Santana

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 308 Post(s)
Liked 3 Times in 3 Posts
1slowride, There are so many combinations of derailleur drivetrains/chainstay lengths that the only practical method is to use either the big-big or little-little method. Both have their strong advocates and while for me the little-little method is my personal favorite, the big-big may prevent sucking the RD into the spokes with a particular combo.

Brad
bradtx is offline  
Old 08-31-11, 08:29 AM
  #5  
Map maker
 
cbchess's Avatar
 
Join Date: Feb 2008
Location: Richmond,VA
Posts: 728

Bikes: Ventana El Ciclon, Walt Works 29er, Specialized Enduro (fixed up for my son).

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked 0 Times in 0 Posts
+1 for big-big plus one link*

*that is only for hard-tail bikes. If you have a full suspension bike you have to un-hook the rear shock and cycle through the travel as some bikes, the Chainstay measurement will "grow" as it cycles through its travel.
cbchess is offline  
Old 08-31-11, 08:35 AM
  #6  
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Posts: 9,438

Bikes: Trek 5500, Colnago C-50

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 7 Times in 6 Posts
For a new build I thread the chain carefully and check the big to big and the small to small combinations making sure that the rear derailleur does to reach its forward or backward limits (does not "bottom out").

When replacing a that I know is right I use the same number of links as the old chain.

Last edited by Al1943; 08-31-11 at 08:40 AM.
Al1943 is offline  
Old 08-31-11, 09:12 AM
  #7  
Senior Member
 
Join Date: Apr 2011
Location: Vienna, VA
Posts: 221

Bikes: Cervelo P3 (retired), Habanero Road, Novara Safari, Batavus Personal Delivery Bike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I use the simplified formula on the Park Tool website. Big-Big does not work for me because I normally ride 11-25 and keep a 13-29 arround for special occaisons. I don't use little-little for the same reasons Sheldon doesn't (didn't, RIP).
TheReal Houdini is offline  
Old 08-31-11, 09:46 AM
  #8  
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656

Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!

Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,095 Times in 741 Posts
Big-big is the more conservative approach, particularly if you set it using the largest cog you will ever use on that chain. Small-small assumes you have a rear derailleur capable of wraping up the entire tooth count and if you do, it does mean big-big will work too.

The problem with small-small is if you have a total-tooth count setup greater than your rear derailleur can handle. For example, I routinely substitute a 26T granny for the OEM 30T granny on road triple cranksets and that gives me a total tooth count greater than the rd will handle. I set the chain at big-big and realize it will go slack in small-small but that not damaging and not a problem. Not being able to handle bib-big can do a lot of damage if an inadvertant shift to that combination is tried.
HillRider is offline  
Old 08-31-11, 11:00 AM
  #9  
Senior Member
 
JonathanGennick's Avatar
 
Join Date: Apr 2007
Location: Munising, Michigan, USA
Posts: 4,131

Bikes: Priority 600, Priority Continuum, Devinci Dexter

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Likes: 0
Liked 55 Times in 37 Posts
Originally Posted by cbchess
If you have a full suspension bike you have to un-hook the rear shock and cycle through the travel as some bikes, the Chainstay measurement will "grow" as it cycles through its travel.
Indeed. I recently performed this exercise on a full-suspension frame I've been riding all summer. Turns out my chain was one link short. I probably got away with that all summer because I avoid big-big when riding, and if I do fall into that combination, it's usually inadvertent during a climb when I'm unlikely to hit a big enough bump hard enough to bottom the suspension. Next time I put a chain on a suspension bike, I will be sure to cycle the suspension afterwards. (It's a bummer that I can't cycle the suspension *before* I cut the chain).
JonathanGennick is offline  
Old 08-31-11, 01:04 PM
  #10  
Senior Member
 
Join Date: Feb 2009
Posts: 6,660
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 582 Post(s)
Liked 171 Times in 138 Posts
You have got to be kidding! The idea of a formula strikes me as rather much ado about nothing.
Shimano recommends that the rear pulleys be verticle when in the large small combo. I just make sure that I can shift to the large large combo without tearing off the derailuer.
davidad is offline  
Old 08-31-11, 08:11 PM
  #11  
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656

Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!

Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,095 Times in 741 Posts
Originally Posted by davidad
You have got to be kidding! The idea of a formula strikes me as rather much ado about nothing.
Shimano recommends that the rear pulleys be verticle when in the large small combo. I just make sure that I can shift to the large large combo without tearing off the derailuer.
As the responses here have illustrated, there are several valid ways to size a chain assuming the rear derailleur is compatible with the gearing. If it is, any of them will work. If it isn't (as in my case) big-big+1" assures you won't break anything.
HillRider is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
TCR Rider
Bicycle Mechanics
11
04-07-16 09:05 PM
deacon mark
Bicycle Mechanics
2
08-15-15 03:29 PM
elblur
Road Cycling
3
02-22-14 05:50 PM
theCan
Road Cycling
7
11-29-12 11:54 AM
micmat
Bicycle Mechanics
3
05-22-11 07:12 AM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.