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 03-09-14, 03:30 PM   #1
nbo10
Junior Member
Thread Starter
 
Join Date: Apr 2012
Location: Ca
Bikes:
Posts: 24
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
COG compatibility

I have ultegra 6700 shifters, rear dérailleur, and a 12-25 cog. Is there a COG that has a 30 tooth gear that would work with my current setup?
nbo10 is offline   Reply With Quote
Old 03-09-14, 03:57 PM   #2
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: 30,017
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 397 Post(s)
A bit more info would certainly help. Such as the number of speeds, short or long cage, and chainring combination.

But in general, RDs have a capacity based on two considerations. The largest sprocket they can clear, and the chain take up capacity, expressed as the sum of the differences largest to smallest, front and rear. For example, if you have 39/53 chainrings, and a 12-25 cassette you need 14+13 or 27 teeth of take up capacity.

Those capacities are listed by the maker on their spec's page. However, there's usually some fudge room, so I find I can routinely exceed them by about 10% or so.

So you can work this out for yourself, by checking system capacity and then shopping among the various cassettes to fit the system.
__________________
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 offline   Reply With Quote
Old 03-09-14, 05:10 PM   #3
shelbyfv
Senior Member
 
Join Date: Jun 2007
Bikes:
Posts: 2,848
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 134 Post(s)
Any 6700 rd will take a 28t cog and the newer ones will take a 30t by design. 6700A? Anyway, it also depends on the derailleur hanger so you will just have to try it. The chances are good however, and a Tiagra 12-30 cassette is only about $25 so it's worth a try. Need a new properly sized chain as well.
shelbyfv 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 10:59 AM.