Suggestions for FD
 

I've got a '89 Schwinn World Sport that was originally 6 x 2 but I've got a 7-sp road triple crankset from the same period that I'd like to put on it (I'm basically trying to build bikes out of all the part that I've got lying around). My clearances seem OK but the original SunTour FD is past it's prime and I don't know if it will handle the triple. I looked online and a 7-sp FD that will handle a triple with a 53T big ring has been elusive. The current FD is a bottom pull, high clamp, with a 28.? clamp diameter as is typical of the Schwinns of that era.

Any suggestions for a replacement? As the R-side Microshifter is friction, could I use a 9-sp FD and just trim with the shifter to accommodate the narrower cage or am I going to be constantly fighting chain rub any time my chainline isn't straight? I'm trying to keep the cost of the FD <$25 if possible as this is a Frankenbike project in hopes of ending up with a comfortable and fun, beater/trainer/Plan B/guest bike without a lot of worries about performance, other than that everything works smoothly.

I've already got a 7sp long cage RD and if my calculations are correct, I should be fine there. Should I anticipate any other problems mixing old 6sp and slightly newer 7sp components? Any other problems I haven't mentioned?

Triple FD have a Wider back Plate of their cage to push up from 1st to middle ,

then the difference between middle to large cannot be too small , because then it wont either clear the middle ring , or,
to clear the middle ring you have to set it higher up than the ideal clearance over the Big Ring..

28.6mm = 1.125", ... frame tubes are usually fractional , except French frames .

My general philosophy is, if I already own parts, I'll bolt up most anything and see if I can make it work to my satisfaction. You're operating with the added benefit of a friction front shifter. That'll overcome a lot of front derailleur issues. If it was my bike I'd bolt that Suntour derailleur up and see what happens. My bet is you'll have no issues at all. Back before index shifting we didn't have specific cage designs for double or triple front derailleurs.

+1. I've used "road" FDs with triple cranks with few issues once they were set up right.

+1 to Retro Grouch's suggestion. Friction shifting is very ecumenical and will let you use a huge variety of mix-and-match derailleurs and cranks.

About the only thing it won't handle is an MTB front derailleur with the cage curvature intended for a small outside chain ring like a 42 or 44T used on a road crank with a 50 or 52/53 large chainring. You would have to mount it way too high to shift well with anything.

If your old Suntour FD is shot, get a Suntour Cyclone off of ebay.

John