bikemig 

I'm getting ready to build a Mercier 300. It has a Stronglight P3 headset. The P3 has a low stack height (34 mm) and the bottom cup is brinelled. I've seen worse but it has indents. The uppers are in good shape as is the crown race.

I'd like to buy a French threaded stronglight P3. I could use an English threaded one I reckon since I really only need the bottom cup. Alternatively I could just buy a low stack english threaded headset and just use the crown race and bottom cup.

deux jambes

I have the Tange copy of the P3. It’s crown race and cups are JIS however. Though it is English threaded. Really nice condition. Pulled from a ‘78 Trek. Don’t know if it’d work for your application or not, but thought I’d mention it.

VeloBase.com - Component: Tange MA-60

bikemig 

Very cool. I did not know that Tange made a copy of the P3. This could work but it will turn on the stack height of the MA 60. I don't think the JIS/ISO difference matters here. The HS is English so I can't use the locknut or the top threaded race but everything else might just work.

The other difference is that the pressed headtube race outside diameter is likely to be a little different (if Sutherland's is right on this). The Tange should be 30.0 mm; a French threaded headset should be 30.2 mm.

I think this should work. Would you mind measuring the stack height?

bikemig 

Good thread on P3 headsets and alternatives here:

https://www.bikeforums.net/classic-v...mm-really.html

deux jambes

Its definitely low stack.
I'll report back with specs this evening after work.

francophile 

I recently sold a stack of Stornlight P3/V4 headset parts, I think it all went to Iniezione

He may be able to help you replace with something stock. If not, and all you need is the bottom cup, I may still be able to help out. I have a few complete headsets in my bins also.

bikemig 

Sutherlands 6th has the stack height for a Stronglight P3 at 34. The lower stack height is 11.1 mm.

It's tough finding another headset that might be available in French threading with this stack height. I realize that for the bottom I can go with a different headset entirely since I can reuse my current top race, adjustable cup, and other parts. Still 11.1 will be tough.

It looks as if a campy gran sport might be a good choice as well. Sutherlands has the stack height at 33.7 and the lower stack height at 11.4. It looks as if a Shimano ultegra 6400 should work (stack height of 33.8, lower stack of 11.6) and a Shimano 105 HP 1050 (32.7 and 11.5 respectively).

There have to be some modern headsets with low stack heights as well. But if it's not French threaded, the bottom assembly cannot have a stack height greater than 11.1.

Charles Wahl

A Tange Levin CDS (not CD, but CDS) has a total stack of 33.3 mm, but the bottom stack is about 12.5 mm. I don't know of any published data on that -- I was also having a headset problem involving a P3 recently, and casting about myself for a solution, with a dial caliper -- and a Levin CDS at hand. But it's unlikely that you'd find one of them with French threading.
I suggest trying to find out whether there's any toleration for a slightly higher stack on your bike, and then find a bottom cup that will fit around your current crown race.