bought a french headset which is the right size but I'm having some problems- the steering feels notchy at when slowly turning the forks. Also, the lower fork cone is loose on the steerer which doesn't seem right.
i've attached some photos and made a video
I'd be grateful for anyone's thoughts.

poggor

that seat looks had it to my eye . Worn out by the look of it.
If it is loose on the fork either something is worn or you need 26.4 but have bought 27mm ?

Thats a dinky wee frame :-)

look forward to more pics of the complete build .

2nd the had it, matching cup looks the same from here, at any rate the whole thing is suspect.

I would measure the crown race seat and get a proper complete HS in good condition since it looks like you have brought the rest of the bike up to a good state.

It will likely be easier said than done as you have found out, finding another complete may be easier, maybe even settle for a UO8 for the time being although they don't turn up cheap when you need them to.

That bottom cup looks like its not seated either, might want to have the facing checked as well.

Digital calipers are your friend here. I bought mine for $10 at Harbor Freight, and they were invaluable in sorting out the issues with my Allegro, which has a French metric Nervor steerer with metric threads. A previous owner had milled the crown race down to 26.4 and crammed on most of an Italian thread headset. In the end I wound up using the lower half of a modern Tange unit with a 26.4 crown race and the top half of a generic Motobecane headset (allegedly made for them by Stronglight).

Is the headset shown separately the one you're working with? When did the PX-10 stop coming with Stronglight V4s?

Your PX10 deserves better than what you're giving it. That's not a Competition V4 nor a P3 headset. It doesn't even look like the headset parts are all from the same headset. If you bought that headset used and someone claimed it was Stronglight, "for a PX-10", "P3" or "V4" you need to return it ASAP, you got robbed. It's possible whatever you're using isn't the correct stack height either.

The crown race shown looks to be pitted to hell. You shouldn't be using captive bearings on the lower race, use loose bearings. If you overtighten or install the captive bearings upside-down, things will feel notchy or rough, the goal is to tighten enough so there's no play after fully tightening down the top nut, but it also doesn't feel indexed (notchy). I'm not sure if you can get there based on what I'm seeing.

If it helps, on the P3/V4/S5 headsets, Stronglight typically stamped their name into the edge of everything except the adjustable cup: On the edge of the crown race, and on the part of the cups that inserts into the head tube (see below). The P3 and V4 had differences, with the V4 having V-shaped bearing races (buttery smooth!) and the outer edge of the top on the V4 cup having a sharp angle almost like the one you posted above (see bottom cup in pic below).

That said, I would start with a proper, complete French headset in this case, something with something correct for the bike. I can donate a mostly-complete P3 headset (lacks the top nut and crown race) if another BF'er can commit to helping get you a P3 top nut and crown race for no more than the cost of shipping.

Adjust the headset after installing the stem. Tightening the stem can distort the steerer enough to make a difference.

OP,
The bottom race has some brinelling and that is why it feels notchy.....also it appears to be too large and should not be able to move freely as shown in your video, also causing some movement....as mentioned use your calipers to check everything in order to be sure sizing is correct.
Best, Ben

thanks for your input everyone- very good tips. I had hoped this headset would work but happy to search for another one.
francophile you are right- she's worthy of more- I have NOS mafac competitions and simplex shifters so I'll find a headset worthy of the build!


thanks everyone

Again, I'll donate parts towards your build, I've done it on other French (and some other) stuff in the past.

Only thing I lack for a complete P3 headset is an apropos Stronglight crown race and P3 top nut.

Anyone have these two bits they could send to OP to complete a P3 headset?

Francophile this is so kind of you- I would really like to take you up on this- even though no one to date has leapt in with spare crown race and nut!
could I PM you?
I'm really having trouble finding a p3/v4 on ebay that isn't crazy expensive (like 400$_)

thanks

Drop me a PM and I can get the headset parts out, possibly tomorrow (wait - just found out you're in Australia. Eek. I always have issues with international shipping, I'm not confident in sending this one out).
That said, I remember seeing (I think) JohnDThompson mention he may have a top nut that could work out in this case, but ... dunno what the result was. Real life has been super busy these last couple weeks so I haven't had as much time to catch up here at BF.