A request was posted about triple vs double gearing. I just built a cross bike with a compact crank so I have an opinion now. I do like the compact better than a triple but I still prefer the standard double since the jump between the 50 to the 34 feels like a huge jump.
Out on the road I see these as advantages over a triple or standard double.
-Lighter overall weight (smaller rings and shorter chain)
-Better shifting than a triple (but no better than double)
-Better chainline
-Smaller gear jumps in the cass but still nearly as wide a range
..most everyone would like a compact if they gave it a shot. The missing top end 40mph+ gear might be a bummer to a select few.
I have a bit more to say but I stole this from the FSA website since they were among the 1st to bring this idea to the masses:
COMPACT GEARING
-What are compact cranks?
Compact cranks are characterized by a 110 mm bolt circle diameter instead of a 130 mm bcd (as in standard cranks). This smaller bolt circle allows one to mount smaller gears on the low end – its now possible to mount a 34 tooth ring instead of the 39 tooth ring which comes with a standard crankset.
-Are compact cranks right for me?
f you spend a lot of time riding in the mountains, your riding style dictates more spinning than pushing higher gears , or you’d like lower gearing but don’t want the added weight/complexity of a triple crankset, compact cranks may be right for you.
-What change in gearing can I expect?
If you keep the same cassette, you’ll lose the equivalent of one gear on the high end, but gain two gears on the low end. Check the downloads page of our website to compare gearing.
Can I convert my 130 bcd (standard) cranks to compact (50/34)?
With a standard 130 bcd crankset, the smallest chainring you can mount is a 38 tooth. On a 130 bcd crankset one can run a 38/50 or 38/48 (a gearing commonly used for cyclocross). It is possible to do the reverse – convert your compact cranks to standard. 39/52 chainrings are available for 110 spacing.
Is it possible to run 52-34 or other gearing?
Not advisable. A normal Shimano or Campagnolo front derailleur is designed to handle a 14 t difference. However, a standard road front derailleur works well for compact gearing (a 16t difference) because the rings are smaller and the physical gap between the two rings is roughly equivalent. Going to an 18 tooth or greater difference will adversely affect your shifting. That's why, when you see a crank offered with a 52 big ring, it comes with a 36 to go along with it.
I want to buy compact cranks. What do I need to do to set this up on my new bike?
You’ll need to lower the front derailleur by 10 mm and readjust the shifting. It’s also recommended to shorten the chain so you’ll have less chain slack with the smaller gearing. Otherwise, if you’re currently running a road double, there’s nothing new you’ll need to buy.
I am having trouble adjusting shifting on my compact cranks.
While a standard road front derailleur is designed around the 53/39 gear combination, we’ve had plenty of luck using Campagnolo or Shimano front derailleurs on compact setups. One suggestion that works for us is: instead of running the derailleur as close to the rings as possible, raise it up by a millimeter or two. This makes the gear change happen not quite as abruptly and reduces the chance of the chain derailing to the inside.
Will my FSA cranks work with my Campagnolo or Dura-Ace 9/10 speed?
Yes, they are compatible with all of the above. The primary difference between the various standards is the chainring spacing. In fact, this difference is so minute that Campagnolo and Shimano’s tolerances for 9 and 10 speed actually overlap each other. We’ve chosen a spacing that is an average of all four standards and which easily falls within the tolerances for Campy or Shimano – 9 or 10 speed.
Out on the road I see these as advantages over a triple or standard double.
-Lighter overall weight (smaller rings and shorter chain)
-Better shifting than a triple (but no better than double)
-Better chainline
-Smaller gear jumps in the cass but still nearly as wide a range
..most everyone would like a compact if they gave it a shot. The missing top end 40mph+ gear might be a bummer to a select few.
I have a bit more to say but I stole this from the FSA website since they were among the 1st to bring this idea to the masses:
COMPACT GEARING
-What are compact cranks?
Compact cranks are characterized by a 110 mm bolt circle diameter instead of a 130 mm bcd (as in standard cranks). This smaller bolt circle allows one to mount smaller gears on the low end – its now possible to mount a 34 tooth ring instead of the 39 tooth ring which comes with a standard crankset.
-Are compact cranks right for me?
f you spend a lot of time riding in the mountains, your riding style dictates more spinning than pushing higher gears , or you’d like lower gearing but don’t want the added weight/complexity of a triple crankset, compact cranks may be right for you.
-What change in gearing can I expect?
If you keep the same cassette, you’ll lose the equivalent of one gear on the high end, but gain two gears on the low end. Check the downloads page of our website to compare gearing.
Can I convert my 130 bcd (standard) cranks to compact (50/34)?
With a standard 130 bcd crankset, the smallest chainring you can mount is a 38 tooth. On a 130 bcd crankset one can run a 38/50 or 38/48 (a gearing commonly used for cyclocross). It is possible to do the reverse – convert your compact cranks to standard. 39/52 chainrings are available for 110 spacing.
Is it possible to run 52-34 or other gearing?
Not advisable. A normal Shimano or Campagnolo front derailleur is designed to handle a 14 t difference. However, a standard road front derailleur works well for compact gearing (a 16t difference) because the rings are smaller and the physical gap between the two rings is roughly equivalent. Going to an 18 tooth or greater difference will adversely affect your shifting. That's why, when you see a crank offered with a 52 big ring, it comes with a 36 to go along with it.
I want to buy compact cranks. What do I need to do to set this up on my new bike?
You’ll need to lower the front derailleur by 10 mm and readjust the shifting. It’s also recommended to shorten the chain so you’ll have less chain slack with the smaller gearing. Otherwise, if you’re currently running a road double, there’s nothing new you’ll need to buy.
I am having trouble adjusting shifting on my compact cranks.
While a standard road front derailleur is designed around the 53/39 gear combination, we’ve had plenty of luck using Campagnolo or Shimano front derailleurs on compact setups. One suggestion that works for us is: instead of running the derailleur as close to the rings as possible, raise it up by a millimeter or two. This makes the gear change happen not quite as abruptly and reduces the chance of the chain derailing to the inside.
Will my FSA cranks work with my Campagnolo or Dura-Ace 9/10 speed?
Yes, they are compatible with all of the above. The primary difference between the various standards is the chainring spacing. In fact, this difference is so minute that Campagnolo and Shimano’s tolerances for 9 and 10 speed actually overlap each other. We’ve chosen a spacing that is an average of all four standards and which easily falls within the tolerances for Campy or Shimano – 9 or 10 speed.