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Old 11-19-09, 09:30 AM   #1
masont
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Question regarding a front derailleur

Hi. I'm new to the biking world, have found these forums to have a wealth of information, but I can't seem to find a suitable answer for a question I have regarding front derailleurs.

I ride a cross bike, and it's got a compact double front crankset (46/34) and it's got a 105 (5500) front derailleur on it. I like to fuss with things, am a bit of a gear nerd, and have found that you can find parts pretty cheap on craigslist with which to upgrade, so I've been converting most of the components I can over to dura-ace 7700. The 105 FD shifts, well, ok. It works, but it takes a minute, and I can't have any pressure on it at all when shifting. So, I'm looking at changing it out.

Here's my question. With a standard road derailleur you're looking at a 14 tooth drop from 53 to 39. On a "normal" compact double, you're looking at a 16 tooth drop from 50 to 34. My bike has a 12 tooth drop from 46-34. I've been told that a compact double front derailleur would be smoother for me, but it seems that it's going in the wrong direction I want it to.

Am I missing something here? Which derailleur would work best with my 46/34?
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Old 11-19-09, 10:17 AM   #2
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I'd probably be looking at mountain bike components. Most road bike front derailleurs have a cage that's designed for the arc of a 53 tooth chainring. Even if it works great it looks a little goofy with a 46 chainring.
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Old 11-19-09, 10:48 AM   #3
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Make sure the current derailleur is perfectly adjusted before you change anything... if your 105 FD is in good condition then it will shift as well as a DA FD. If you have a modern crankset with ramps and pins on the chainrings then there should be no hesitation or missed shifts, unless the derailleur is improperly adjusted.

A mountain front Derailleur will not work well as they are designed around a different amount of cable pull than road FDs - strictly speaking, mountain FDs are not compatible with indexed road shifters.
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Old 11-19-09, 12:41 PM   #4
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Originally Posted by LarDasse74 View Post
Make sure the current derailleur is perfectly adjusted before you change anything... if your 105 FD is in good condition then it will shift as well as a DA FD. If you have a modern crankset with ramps and pins on the chainrings then there should be no hesitation or missed shifts, unless the derailleur is improperly adjusted.

A mountain front Derailleur will not work well as they are designed around a different amount of cable pull than road FDs - strictly speaking, mountain FDs are not compatible with indexed road shifters.
It's an fsa energy crankset. I'm not sure what ramps and pins are.

I'll look at adjusting the fd first. Is the main difference between a compact specific and road fd the arc, or the distance between chainrings?
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Old 11-20-09, 09:11 PM   #5
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Ramps are specially shaped teeth on the chainrings and cogs to allow and assist the chain to move between gears. Pins are... well... pins that are mounted on modern chainrings to help grab the chain and lift it to the next chainring during shifts. FSA cranks usually have these.
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