# Is switching your bike to a Compact as easy as changing chainrings?



## lacofdfireman (May 2, 2010)

Looking for a used bike but would like a compact. Seems there are more 53/39's out there than 50/34's. So can I change to a Compact as easy as swapping out chainrings or do you have to do other stuff? I would imagine you would have to drop the front derailleur but not really sure. And with a bike that wasn't a clamp on derailleur that might not work. Figured I would ask the experts...


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## frdfandc (Nov 27, 2007)

IIRC, FSA Makes a 50 tooth chain ring in the 130 BCD, but the smallest inner ring would be a 38 due to the 130 BCD.

So to go to a 34 inner chain ring, you would need to swap out the entire crank, install the new compact crank, and make a front derailleur adjustment.


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## cdhbrad (Feb 18, 2003)

You will need to change your crankset to get a 50/34 chainring combination, since your current crankset probably has a 130mm BCD, but to get a 34 tooth ring, you will need a 110mm BCD. You can find 50 tooth rings in 130, but not a 34. Besides that, shorten the chain and drop the front der. to the proper height and you are ready to go.


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## Camilo (Jun 23, 2007)

What these guys are saying that the word "compact" actually refers to the bolt pattern of the crank, not the rings themselves.

Regular road cranks have a 130mm bolt center diameter (BCD). Compact cranks have a 110mm BCD. Therefore the rings they can mount can be smaller. You can set up a compact crank with rings very similar in size to a regular crank, but not vice versa. 

Look at this site to get an idea of what your possibilities are for the 130 vs. the 110.

http://sheldonbrown.com/harris/chainrings.html


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## PRB (Jun 15, 2002)

lacofdfireman said:


> I would imagine you would have to drop the front derailleur but not really sure. And with a bike that wasn't a clamp on derailleur that might not work.


 I've ran a 50T on three different bikes with braze on front derailleurs and never had a problem.


Camilo said:


> Regular road cranks have a 130mm bolt center diameter (BCD).


Don't you mean 135mm?


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## Camilo (Jun 23, 2007)

PRB said:


> I've ran a 50T on three different bikes with braze on front derailleurs and never had a problem.Don't you mean 135mm?


Io non parlo italiano


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## Hughsdad (Jan 21, 2011)

Camilo said:


> Io non parlo italiano


:thumbsup:


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## JacksonDodge (Mar 26, 2006)

PRB said:


> Don't you mean 135mm?


130mm is correct.

Campagnolo uses 135mm BCD.


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