akexpress 

I am helping a friend work on his Calfee recumbent and we are having front shifting issues. It has a Ultegra derailleur with Xtr flat bar shifters. 55/44/30 chainrings and has trouble missing the middle chainring on the downshift. Can anyone confirm that there needs to be 14 tooth difference to make it shift right?

Leisesturm

Your scenario is unclear. I do not understand "missing" the middle chainring. Are you saying that on a shift from the 55 the chain bypasses the 44 and heads directly to the granny? The common problem with front derailleurs is the chain missing the very lowest chainring and winding up wedged in the crook of the frame. Problems at the extremes (outer rings) are adjustment issues with the limit stops of the derailleur (usually). A problem with a middle ring sounds like bent or missing teeth. FWIW.

H

Carbonfiberboy 

AFAIK, the max tooth difference is about 14 and less is better. Try loosening the outer limit screw and increasing cable tension until, while in the big ring, you only have a couple of mm of clearance between chain and the inside of the cage while using the largest cog you would use in the big ring. On a DF bike, you might have to trim in the middle ring to access the innermost cog. With that large a difference between middle and inner rings, I'd install a chain stopper to prevent frame damage.

akexpress 

Yes it misses the middle chainring and goes straight to the small ring and them you have to shift back up. Shifting from the small to middle and to big works fine it it just the down shifting. A K-edge chain catcher is installed to prevent shifting off the small and wedging. No teeth missing or bent, new lighting cranks. I will take pictures of the bike. A Calfee carbon recumbent tandem with couplers, the only one in existence. Just having trouble fine tuning the front derailleur.

tredlodz

Which Ultegra FD are you using? If you use FD-6503 or older it's designed for 52-42-30 ie the 10 tooth step you want. As far as I know FD-6503 works for 10 speed just fine. I use it with dura-ace shifters on a 9-speed system with 54-44-28 (+jump stop).

Newer FDs 6603, 6703 (for no good reason) are designed for 53-39-30 or 52-39-30 triple set ups. The low end of the plate hangs down lower to help with the 13 or 14 tooth middle-large jump, so it tends to interfere with the middle chainring if you use something bigger than a 39 middle ring. So you have to set it higher than you want.

So if this is the issue, your options would seem to be
1) Try a 42T or smaller middle ring.
2) Buy a FD-6503 shifter on ebay (Campy may work better too)
3) Drop the FD as low as you can and fudge the middle position on the high end. You can use the limit screws to set up the small and large positions but the middle needs to be dialed in on the screw adjuster. Set this up without worrying about the other rings.

Good luck!

akexpress 

Thanks for all the advice. We spent about two hours going thru the drivetrain. It was the first time in the stand for me to look at it. It had been put together with a 52/44/30 and mixture of shimano and TA chainrings, two alloy and one stainless (???). Because of this the derailleur was mounted very high and the inner cage hit the middle chainring. In addition they had mounted a K-edge in such a way that it hit the cage also. I was very surprised that a high end company would do such a poor job. the bike is spectacular but their execution of the build was not well done. I replaced the large and middle rings with shimano 53/39 and positioned the derailleur and K-edge correctly and now it shifts great. Also the chain was too long and had a weird cable run to the rear derailleur that with some creative modifications I got to enable a clean run. this bike has a very long chain and has to idlers to keep chain bounce to a minimum, one of the brackets for the idler was in the way of the rear cable so I was able to drill a hole in the bracket for the cable to run through and make a clean run. Again thanks for all the advice.
Mark