zolaman

In a prior post (not sure if a better way to do this but here's the URL: https://www.bikeforums.net/classic-v...l#post21793392) I requested help in identifying my French frame - i.e. was it really a PX10. Pictures were posted. I will provide some closure on that post with post painting pics and further details.



From that post, here is a picture of the fork crown race. It's to a Stronglight Competition (V4, I believe). It shows it "installed" as it's been since it was last built after the blue powder many years ago. Well after the stripping, media blasting and repainting, that crown race doesn't fit! Measuring, the inner diameter, at the point where it meets the crown, is 27.0 mm. My fork actually measures at 26.5, which I read per Sheldon Brown is the expected spec on a French steerer. All I can guess it that the steerer had been painted so thick that the race more or less fit snug - tho clearly not correctly.

I'm now searching for a good quality replacement headset since it would appear that finding the correct crown race at 26.4/5 mm, to fit with the rest of the Stronglight headset, is unlikely. Anyone have one to spare?
I'm investigating sources for a new Stronglight A9 FR, though I'm also trying to confirm that it is 26.4 - I think I know it should be but the Stronglight specs don't seem to confirm it.
The headtube diameter is 30.2 of course and I have an available stack height of 38mm - (or I'd likely consider the Velo Orange French headset.)
Without spending a fortune, any other recommendations?

Thanks!

oneclick 

Get a good bike shop or friendly person with a lathe to knurl the crown seat.

JohnDThompson 

Find a shop that can knurl the race seat, as [MENTION=512318]oneclick[/MENTION] suggests above. It doesn't need to be done with a lathe; Stein has a tool that can do it in a bench vise:


https://www.steintool.com/portfolio-...knurling-tool/

Jeff Neese

Velo Orange has a headset for it.

https://velo-orange.com/collections/...thread-headset

zolaman

Shouldve mentioned that it appears that it had previously been manually “pinged” to raise the effective diameter. But it’s still quite loose. Wondering if your suggestion- to have the crown seat machine knurled - would raise it sufficiently?

Charles Wahl

I think you mean "peened", but if not, shame on me. I have a similar problem with a couple vintage English forks: came to me with crown races (that I believed to be original) having 27.0 ID, but the "meat" on the base of the steerer tube measures smaller. In both cases, the crown race just fell off when disassembling. So I feel your pain. French is harder, unless you want to have the steerer base milled to 26.4 mm. I'm not so sure that I would expect knurling to increase the diameter of the seat 0.6 mm (from 26.5 to 27.1) for a proper interference fit, especially if it's already been "aggrandized" mechanically in some way.

zolaman

Thanks! I'll check around.

zolaman

Stack height on that one is 41. I've got 38 mm available.

zolaman

Yeah, peened is good - lol. Though I'm no machinist, I recall from shop class (~ 1 million years ago) that one used a ball peen hammer to peen. This looks as though someone used a pointy punch of some kind and hammered little craters into the crown seat (the "meat") to raise it up. I'm also somewhat dubious of knurling the crown seat being sufficient to raise it enough for a solid fit.

Just got a price on the Stronglight A9 FR from Peter White ($118 - plus shipping, I assume). Wowzers... not sure this bike is worth spending that, tho it is looking might pretty with its new paint.

Another thread on this topic resolved with the OP finding some 0.010" brass strips at his hw store and using that to shim the too large race to the crown. I may try going that route.

oneclick 

I don't think peening would be the right word, that's a method of depressing a surface, commonly for compressing the skin of a metal part to reduce crack initiation/propagation; for example motor-car connecting rods are sometimes shot-peened, and cast-iron welds should be hammer-peened while hot.

He may be describing what home-shop mechanics would do - make a series of punch-marks with a good small hard point; the metal displaced from the point of the punch would raise a ring around it; punch enough points and you have a surface covered with such rings, all high enough to increase the effective diameter.

And yes, I would expect knurling to easily arrange the surface of a 26.5 crown seat so that it would fit - and fix - a 27.0 race in position.

bikemig 

Finding a low stack French threaded headset may be difficult. The Stronglight P3 is low stack but difficult to find.

First you need to sort out the crown race diameter. Second, the top doesn't need to match the bottom. The top has to be french threaded but there is no threading on the bottom. So you can use the bottom from a different headset to make this work. Even the bottom from an english threaded headset should work.

speedevil 

To tighten the crown race, you might try SKF Speedi-sleeve part 99103 which just might stretch over the steerer.

Or, wrap the steerer with foil making a sort of spiral ramp overlap so that crown race can glide over foil without tearing.

Either of those methods have worked to tighten a crown race to the steerer - good luck.

thumpism 

"Staking" might be the word you're looking for if a crown race is too large for the crown. Take a chisel and go around the base of the steerer where the race will seat and tap the chisel to raise a series of ridges around the steerer and the race will slip down over this area and be held fast. I've done this several times.

https://en.wikipedia.org/wiki/Staking_(manufacturing)

Like this, only different.

zolaman

Ended up buying a 4”x5” piece of .01” brass shim stock. Cut a piece about 4 mm wide by just short of the crown race seat circumference. Fitted that to the tube and wedged the crown race over the strip. By hand it went on very snugly but not fully seated. Took it in to my LBS and asked John to bang it in place. Good to go! Thanks for all the input.

By the way, in all my searching for possible headsets I came to know that my Stronglight Competition V4 would likely fetch a nice price - but I’d rather have it on my bike! 😄

JohnDThompson 

The Competition V4 headsets used a V-shaped bearing race which creates two bearing tracks in each race (typical parabolic races have only a single track), thus spreading the load over more area. This makes it a very durable unit, but also fussier about alignment. Did your shimmed crown race align properly (no binding or slop when assembled)?

zolaman

Yes it’s solid and square on the fork. Thanks!

rustystrings61 

I had a similar problem a few years back with an old Allegro that a previous owner had hamfisted an Italian-threaded Campagnolo NR headset onto a Nervor metric steerer cut for a Stronglight P3. To make it work they left out washers, spacers, etc, and the locknut was barely threaded on. They had cut the crown race for a 26.4, though. In the end I used the top half of a basic steel Motobecane French-threaded headset (I think Chas./verktyg said once they were O.E.M. units actually built by Stronglight) with a Tange lower headset unit for a 26.4 crown race. Works beautifully.