PX-10 Headset Install Question
 

Bottom of the head tube is threaded but the lower Stronglight Competion bearing cup that fits into the headtube is not.

Simply insert the unthreaded end of the bearing cup into the head tube? If so, does anyone know why the bottom end of the head tube is threaded?

Do I have the wrong Stronglight headset. I believe it's a Competition v4.

Looks like this one:

https://cimg5.ibsrv.net/gimg/bikefor...9b12731cd5.jpg

Looks like I purchased the wrong headset. Need a threaded set.

I don't have an answer, but was the one you removed original? The lower cup was not threaded, correct? Could what looks like threading on the lower head tube be some type of machining/milling marks instead? I have never heard of threaded head tubes, but I've never had a French bike!

My first French bike. Both ends of the head tube appear to be threaded but having said that, I could easily tap both the top and bottom bearing cups into the head tube.

I purchased the entire group from a Forum member. He took it off one of the many PX-10s he had.

Hears a pic of the headset I have (Stronglight Competition):

https://cimg2.ibsrv.net/gimg/bikefor...f5ca2eed68.jpg

I’ve never heard of threaded head tubes. Do you mean the head tube has threads cut into it?

I doubt that it's threaded, it is just probably how it looks like because of the reaming of the head tube.

Yes but perhaps intentionally machined that way to give the cups some "bite" when they pressed in?

After digging through some online threads, beginning to look that way.

This is how the head tube is reamed on my RR10. I guess it's similar to what you have on that PX10
https://cimg1.ibsrv.net/gimg/bikefor...596f0dbc4d.jpg
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Already sent this directly, but here's the end-all-be-all of info you'd want on the Stronglight P3, V4 and S5 headsets: Stronglight headseta

The V4 has V-cut grooves for the races, if I recall. Easiest way to distinguish between it and what the P3 uses, and to tell if you have a mis-matched headset. I find the V-shaped races lend to a smoother experience, but that's entirely IMO.

That said, the cups here are press-in, no threads needed, just like many other headsets. It's not uncommon to find ridges like what you're seeing in the head tube, the top and bottom cups are still press-in. The only two threaded pieces in the headset are the top nut and adjustable race with "alligator teeth" which lock into the space under the top nut.

The stack you show in the 4th post above looks to be complete V4 headset (judging by the top nut) assuming there's a crown race under the bottom cup. I have no idea what that is in your 1st post, I've never seen that top nut before.

The V-shaped crown race was intended to be more durable than a traditional parabolic race by providing two bearing tracks in the race to spread the wear. The problem with it was that it was very fussy about alignment compared with a parabolic race. The later A-9 and B-10 roller bearing headsets addressed the alignment issue by using floating races.

Yes. Exactly.

Thanks. No v-cut on the races. Top lock nut is v4, however.

​ I pressed them in without much difficulty. Just a few taps with a rubber mallet. As you noted, turns a bit stiffer than others I've had.

Note: I'm not an expert on Stronglight gear. It's very possible the P3 switched to the same top nut as V4 later, but I bought a few different well-priced headsets off the big auction site over the years which arrived with mixed races, spacers and cups. It't not uncommon apparently, but in the case of top nut, I personally think negligible. I think the top nut on the V4 looks better, think it'll alter stack height a hair, possibly in your favor.

Sounds like you may be getting closer! If this thing ends up anywhere near as nice as the Circuit buildup, it'll be a treat to see!

I suspect those gouges may be a result of not bothering to clean the swarf off the cutters between frames.

Cleaning the cutters takes time.
in a bad humor after Summer vacation?
notice very often there are labor strikes in France in early October?
cranky workers

Looks to me like dull tooling run aggressively at slow speeds. My Herse has the same markings on a lot of alu parts. Seems to me they didn't sharpen tools as often in those days.

Knurling of press-fit surfaces is commonly used to allow for more-relaxed manufacturing tolerances, so perhaps the texture was a deliberate thing in the headtube's bore(?).
Schwinn used a more pronounced and different style knurling on the outside of the steerer tube, where the crown race got pressed on. This was on the lower-tier bikes up to and including the Supersport, where this knurling often was a bit less than sufficient in making up for an otherwise very loose fit.

In other applications, knurling may be used to act as an assembly spacer for a liquid adhesive or sealant (to keep the adhesive layer to a more-consistent thickness), or to restore worn parts.