Derailleur adjustment with compact crank

[lunacycles]

Front derailleurs specifically designed to work with compact cranks are usually put into use to help prevent dropping the chain to the inside of the small ring due to the big differential between c-ring sizes...not the issue you are having. I would recommend checking the angle of the cage over the big chainring, and make sure it is exactly parallel, also that the FD sits only about 1mm above the chainring teeth (i.e., as close as possible).
I run an FSA compact crank with Ultegra FD and have zero problems.

[HillSlugger]

Front derailleurs specifically designed to work with compact cranks are usually put into use to help prevent dropping the chain to the inside of the small ring due to the big differential between c-ring sizes...not the issue you are having. I would recommend checking the angle of the cage over the big chainring, and make sure it is exactly parallel, also that the FD sits only about 1mm above the chainring teeth (i.e., as close as possible).
I run an FSA compact crank with Ultegra FD and have zero problems.

Margo, thanks for the insight.

Because the curve of the FD doesn't match the curve of the 50T ring the spacing between FD and crank varies at all points. I know I can't lower it any more or the chain can't get onto the big ring.

With a braze-on FD how much adjustment do I have for parallel? Should I give this another try on my own or drop it off at the LBS and hope they can work some magic? Why did it work perfectly last week but fail me yesterday?

[lunacycles]

With a braze-on FD how much adjustment do I have for parallel?

You should have some. Often the derailleur and the braze on fall in love in a certain position, but if you hold the derailleur firmly in the alternative, more ideal position, it should move a bit for you. Definitely try it again...what have you got to lose? Derailleur adjustment stuff tends to be finicky more often than not, and so often requires patience and at least a few tries til you find the sweet spot. Good luck.

[HillSlugger]

You should have some. Often the derailleur and the braze on fall in love in a certain position, but if you hold the derailleur firmly in the alternative, more ideal position, it should move a bit for you. Definitely try it again...what have you got to lose? Derailleur adjustment stuff tends to be finicky more often than not, and so often requires patience and at least a few tries til you find the sweet spot. Good luck.

I had the bike in my car so I could take it by the LBS; the alignment looks good to me.

Anyway, I swung over to the LBS after work. The wonderful mechanics there took a look at it right away, made some adjustments on the spot, and returned the bike to me. Hopefully this will work.

When I wheeled the bike into the store one of the staff said "Wow, what is that? I've never seen a bike like that!" This really made me smile

[divingbiker]

I had the bike in my car so I could take it by the LBS; the alignment looks good to me.

Anyway, I swung over to the LBS after work. The wonderful mechanics there took a look at it right away, made some adjustments on the spot, and returned the bike to me. Hopefully this will work.

When I wheeled the bike into the store one of the staff said "Wow, what is that? I've never seen a bike like that!" This really made me smile

Is this your tri bike you're fiddling with? Did you take it to Proteus or somewhere else?

[HillSlugger]

Yes, the tri bike. I took it to City Bikes since they are the most convenient for me.

[aicabsolut]

If you still have problems, bring it to me. I've used 105, Ultegra, and DA front derailleurs on FSA and DA cranks. The 105 or ultegra setup on the FSA cranks with a clamp-on FD was the most finicky. The DA/DA braze-on match is amazingly awesome. But, if it's an alignment issue, I will be able to fix it. I usually have to totally re-do the FD on the FSA bike after the shop messes with it. So, I learned how to do it pretty well. If the cage needs to be moved, it can be a pain. You don't have as much range with a braze-on, but it can be moved a little bit.

However, I'm thinking that since this is your tri bike with non-indexed shifting in the front, some of it is going to be user error. Maybe you aren't used to the throw of the lever yet. Some compacts are a little more finicky about what rear cog you're in when you shift (are you any more successful shifting from the smaller end of the cassette?). Even so, it should be relatively rare to get the chain to go off to the outside if the FD is adjusted right. It's a lot more common to have drop to the inside with a compact.

You might try re-setting the limit and then tightening the cable tension if it gets a little sluggish. Adjust the FD upper limit screw a TINY bit at a time, and while you're in the little ring.

[amartha]

Having just converted a triple to a compact crank on one of my 5 bikes, I have learned a lot.

I needed a 165 mm 9-speed crank for my short legs. The only model available was the Shimano Sora. I liked it -- much lighter than the Truvative triple.

FSA 9-speed compact cranks only come in 170mm lengths which would cause me too much toe overlap with the front wheel.

The compact crank works with a double front derailleur and triple rear derailleur. I replaced a Shimano Tiagra triple front derailleur with a Shimano 105 double front derailleur.

The compact crank must mate with its bottom bracket. I replaced a generic Truvativ triple bottom bracket with a Shimano hollowtech.

The Shimano 105 triple rear derailleur works perfectly!

Depending upon the other components -- 10 speed or 9-speed rear cassettes and shifters, the compact crank doesn't need Ultegra level, especially if the rest of the compenents in the drive train are less than Ultegra-level in quality.

[aicabsolut]

Why are you using a long cage rear derailleur?

[Cataboo]

maybe 'cause she had it from the triple that she was converting to a double?

[HillSlugger]

My FD has been well behaved on my last two rides but yesterday the RD decided that it wanted to skip past one of the cogs towards the middle of the set. Everything else seemed OK. What would cause this all of a sudden and what do I do to fix it?