With a braze-on front derailler tab originally positioned for standard road rings, I assume there will be a conflict trying to run a compact crank, that the der. won't be low enough. Any solutions? File the tab slot? Some kind of adaptor? New front der.?

They typically have a decent range of adjustment. Have you installed both the crank and the derailleur yet or are you only worrying about an issue that may or may not exist?

I'm pre-worrying, haha. Hopefully it won't be an issue but I wondered if others had dealt with this before.

Ha!

Do tell, what crank/rings/BB spindle are you using and what FD?

well I was going to wait until the build to reveal...but since you ask, I was the buyer of gioscinelli's merckx 7/11 frame and fork:


and I intend to move the parts from my '89 paramount over to it:

for the most part, I may opt for some different parts, not sure yet.
Crank is a sugino alpina compact w/ phil wood BB. Rear and front der. are dura ace 7400 8speed.
Hopefully robbietunes won't suffer too much angst over the switch, he's familiar with my paramount!

Cool! Congratulations.

So a 48t big ring? I'll bet you'll be fine. With a crank with lower Q you may have FD cage rubbing issues, but probably not with the Sugino.

I've never had an issue, but just for fun if you compare the diameter of a 53 vs. a 50 ring, they differ by about 12mm (I calculated this, but I haven't measured it on any actual chainrings). So that means the radius from the BB center to top of ring only differs by 6mm. I would think half a centimeter is something a front derailleur might be able to handle even if you weren't able to move it.

My compact is 48/34, hopefully not so much to matter.

Whoops, I used the wrong tooth count. Diameter of 48t ring is approx 195mm (D = 12.75 * T / pi). So difference between 53 and 48 is 20mm diameter or 10mm radius. One centimeter to adjust.

FWIW I tried to put a compact on my brother's 2300 and the tab was not low enough. 50/34 rings.

I have an '85 Corsa Extra - which is near identical to op's bike.
My Record crank, w Record BB, has a 49T ring on it.
I'm using a Record FD.

There's still room to move it down more than 2mm.

I stuck a 50/34 FSA Gossamer on my '86 Cannondale and had room to move the front derailleur (Shimano 105) down.


Seemed to approach the limit, but works fine.

The correct answer is that you may or may not have a problem going to a 48.

That's getting quite a bit smaller than a 52/53, which is generally where the braze-ons were centered. However, that positioning assumed a front derailleur "drop" so the derailleur that you use may be a factor also.

Try it and see (is the only way to determine whether it will work or not...).

I bought an adaptor from a trek dealer for a few bucks that worked great. It was a listed part for an early trek 5000. I don't remember what it looked like or if it would work on steel.

I think this would work (if necessary)...~$9

The Campy tech spec for positioning the FD tab shows a 10mm difference between the position optimized for a 48 vs 53. I don't see a reason for Shimano to need anything different The slot in the tab is probably 20mm so you probably won't have a problem. Worst case, you might have to file a little bit but I'm betting you won't.