lajt

I'm learning the hard way how intimately related the crank, chainring, front derailleur, and braze-on are for my first '80s road frame buildup.
For the crank, I got a Sugino 46-34. (I'm not a strong rider these days so I find it easier with a compact.)
That added to the complexity immensely, I'm discovering.
Next I get on Ebay and am faced with the deluge of braze-on front derailleurs.
"Hmm, well, here's a neat braze-on Gipiemme, that kind of goes with the Italian frame, I'll go with that."
As shown in the 1st pic below, the fit isn't even close.
I find a nifty Wickwerks bracket that can lower the derailleur, so I get that, but now it's too low, as shown in pic 2.
I figure I should try a plain vanilla, clamp-on Japanese derailleur from the 80s instead. Also doesn't work, as shown in pic 3.
I finally borrow the derailleur from my son's bike, and it actually seems like a decent fit, although the derailleur arc doesn't match the crank arc. Not sure how important this is.
I'm not a big fan of his derailleur because it has a tendency to rub, and the angles of the cage make it harder for me to visually adjust. I was hoping for a flat cage.
Still, it's the only one of 3 I've seen that is even close.
Should I be looking at mountain bike derailleurs instead because this chainring is so small? In order to get the arcs to match better, I mean?
Otherwise, if I had any hope to put an old Shimano 105 or 300EX or Dura Ace derailleur on there, is there any way to determine what might fit outside of blindly ordering and trying them?

bark_eater 

IRD makes a braze on FD for compact cranks. The might be able to give you the critical dimensions to confirm before ordering.

https://www.interlocracing.com/shop/...rch=derailleur

Your Exage derailleur is low profile enough to fit under the Braze on. If you had one with a 31.8 clamp you might be able to use tapered shims to get there.

I have a bike with a 46 outer ring and a Exage Motion? FD and it shifts fine. I'll try and get a picture later today. I remember playing with it a while to get it to work, but its a flat ring, so your rings might be an advantage.

sd5782 

That’s a nice looking crank too. I searched it and found on eBay for a nice price. Members here have been looking for economical compact cranks, and also for that 34 tooth chainring. Hope you get it worked out.

rccardr 

46 with a braze on mount is hard. Couple of suggestions:
Look for a FD that has a mounting bolt in the middle or upper end of the body as well as a long body and low cage. That Gipiemme has a bolt closer to the bottom of the body, which raises the FD relative to the mount. Maybe a Shimano Cross series (CX50, CX70) as they are meant to be used with smaller chainrings. Also look at Triple FD's as they tend to have a longer body/lower cage to deal with smaller inner rings.

Drill and tap another bolt hole closer to the top of the body is there's enough meat to deal with it. You don't need too much to make this work, especially if you also use a rat tail file to elongate the bottom of the hole in the braze-on.

Ultimately, though, you may have to choose between an FD that's too high, a larger (48?) chain ring, or shaving off the braze on mount, touching up the paint, and using a clamp on FD.

DorkDisk

FWIW, my experience says to match the derailleur with the shifter. Matching curvature is nice but not necessary. I currently have a 38/28 crank with a ultegra 6700 unit working fine with indexing. Friction makes it even easier.





friction shifting

Spaghetti Legs 

I have 2 bikes with compact cranks and braze on FD. The 48-34 Velo Orange uses a Centaur 10 speed and the Sugino 50-34 uses a Record 8 speed. Both shift fine.

jamesdak 

I've got no suggestions other than what has been said already. First time I've seen one of the Wickwerks one's. The owner of Wickwerks is a buddy and workmate of mine. Great guy!

lajt

Thanks everybody for the lifelines. I ended up taking Doc/ rccardr 's suggestion and drilled/tapped a new hole. I think I just leveled up my wrenching ability. I've never attempted tapping a hole before--I figured I would just consider the hacking on the derailleur as a sacrifice toward educating myself if I ruined it, but it totally worked! I haven't mounted the chain yet, but it's looking pretty promising. Pics below.
jamesdak , what a cool/small world coincidence that you know the owner of Wickwerks!
Spaghetti Legs and DorkDisk , thanks for showing me that your bikes have road derailleurs with compact cranks; that eases my mind about the arcs not matching.
barkeater , thanks for the link to the IRD derailleur. That is plan B if this doesn't work.
sd5782 , thanks about the crank! Haven't ridden with it yet but I'm definitely digging the look of it.

rccardr 

Nice work, looks good!

Spaghetti Legs 

Serious wrenching there. Good job!