Compact Cranks and Front Deraileur
 

I been thinking for awhile about trying out a compact crank so today I picked up a Ritchey WCS 110 V 50/34 at a great price. I went to see my favorite mechanic to chat with him about the bike I wanted it for and he said because the frame uses a braze on deraileur it would be difficult to impossible to properly adjust the Ultegra FD currently on the bike to work with the Ritchey compact crank. He suggested that I purchase the IRD deraileur designed for use in braze installations with a compact crank, http://www.interlocracing.com/cdfrtder.html. By the way, his shop doesn't sell them, so he wasn't looking create a sale. In any case, I went ahead and ordered the IRD CD Deraileur from Excel Sports and I'm sure it will work just fine. The question is, did I really have to buy it to use the compact crank, or could the Ultegra FD be adjusted to work correctly?

I am still trying to figure out which front der was on my bike when I got it. It has a compact double, and the der is Chorus, but does not match any pic I can find in the Campa catalog or spares manual.

The reason I care is that I can't seem to adjust the interference out of it when I am in 50-13, which seems wierd. It is OK in 34-29. And I can't find out where the rubbing occurs, which is even wierder.

Bottom line to me is that with a compact, selecting the front der needs careful attention.

The primary reason to change FD's when installing a compact double is due to the radius of the compact big ring being smaller than that of a conventional double (or triple) FD cage. In theory having the appropriate smaller radius FD cage will promote better shifting...without rub on the rear spar of the cage (vertical)...as it will better shadow the bigger ring. Many who have converted to a compact double however have used the original FD and their shifting was just fine.
Before converting, I would try the original FD, albeit adjusted for height (lowered) due to the increased clearance between the FD and compact double larger chainring. Perhaps blandin you don't have the same level of adjustability as band clamp FD's do with your braze-on FD.
Lastly, gmason, if you have a std. Campy ergo FD with adjustable trim on your compact, your rub likely isn't in the horizontal or X-chain plane or sides of the FD cage rubbing when running from biggest compact ring to smaller cogs. It is likely due to "vertical plane" rubbing on the rear FD cage spar...running from big compact ring down to smaller rear cogs...why a compact specific FD is recommended. A suggestion would be to check the vertical height/clearance between FD cage and largest compact chain ring...should be just a couple of mm's clearance maximum. This distance becomes more critical when running a compact outer ring with a conventional FD cage as the shape of a compact large ring drops down away from the FD cage in the back...the FD cage being a bit higher in the rear promoting chain rub on the rear spar of the cage when running a compact big ring and small rear cogs. Horizontal or across the bike chain angles are tuneable with cable tension as the compact and regular double should share the same distance and location between chainrings.
George

That's nonsense.

Sometimes with a barzeon, it's not possible to lower the FD enough to worjk with a 50 ring,but that's unusual,and often can be fixed with a dremel tool to the hanger. I don't know that it's a given that the IRD in itself cures this problem.If he didn 't actually try the ultega in your application, I suspect he was just blowing smoke.

Nothing to back it up only confirms what most know...you have no idea what you are talking about.
George

Suggest you go look at one or draw yourself picture. When in the 50/12 the chain is nowhere near the 'spar' on my standard FD. :rolleyes: Different senario when in the small/small, but still nowhere close to rubbing the 'spar'.

No need for any pictures...lol. I stand corrected...I just took a closer look. Then gmason there isn't a plausible explanation for your rub since your Campy FD can be trimmed...other then gremlins.
Aside from aesthetics then, why would one change to a compact specific FD?
George

Given that the problem is in the big ring ,small cog,trim has nothing to do with it,but position,alignment and hi limit adjustmet does.

First you didn't answer the question...what a surprise. Second...adjustment affects
ability to trim the cage away from X-chain rub. I see you finally learned that adjusting the high limit screw if set too loose can affect X-chain rub on the inside wall of the FD cage.
George

I think you ought to go back to bed and give it a try tomorrow Georgie. As I read it the problem is in the big ring and small cog and would be rub on the outside of the FD cage.The hi limit might be set a bit too tight.

For once I agree with you...lol.
George

My thanks to biker7 and sydney, not only for their insight into my deraileur issue, but for their fascinating banter that brightened an otherwise quiet Sunday morning! :p

yeah...we are known for that. Call it good chemistry.
;)
George