Vintage Replacement Fork
 

I would like to replace the fork on an old Jeunet 12 bike with a 24 1/2" frame and 27" tires My LBS can only recommend finding one on an old bike. I've been wondering about ordering one from a custom frame builder. Any suggestions?

1" threaded forks for 27" wheels are still available new. I don't know what kind of quality you are looking for, but this fork is available in a number of steerer tube lengths. https://www.modernbike.com/dimension...m-of-threading

A Google search will reveal numerous other options.

I have never seen any Jeunet bikes that were worth the kind of money that a custom fork would cost. I imagine they made some, but my experience was limited to bikes that were very similar to a UO-8
Figure $400 plus paint.

Jeunet was a contract job, made by a manufacturer for a client (much like Giant does for other brands). They had a number of grades over the years. I have read of a couple with 531 tubing and high end French components with sew ups. The one I had was a cheap version of a Peugeot UP-8. I have to admit that back in the day I wanted their high end version for a little while (until the Fuji Finest came into my life).

These days replacement forks for a 27" wheel are not unknown but fewer then other current wheel sized forks of today. Most will be made of HiTen steel (think above UO-8 grade) with two choices of steerer lengths and a lot of threading to allow cutting to size. 27.0 fork crown seats and either black or chrome. Stamped drop outs that might have top be filed a bit for a QR diameter axle. Retail from $30 to $50 is typical.

But in today's pandemic starved supply chain these might be out of stock for a while. Here south of the boarder the supplier JBI lists a few available. In Canada I can't say.

Eric is pretty correct in his estimate of a custom fork cost from a reliable builder. BTW do you know the potential fork's dimensional specs? (and that's all together another thread...) Andy

That's the low end for a fork nowadays, although I have seen that there are a couple of guys that will build for less. Which I fail to understand. Don't remember any names either.

I should have added that most any after market fork won't be French spec, as the Jeunet was. So include a stem and maybe bars and headset in the cost estimate. Andy

Thanks, everyone. I was just looking for a ballpark estimate to see if it might be worth saving. It is 531 double butted, but very worn out. The steering tube is stripped, so I suspect the headset was mismatched at the store, leaving me to determine what it is. The front hub is French, but not the BB.

What about steerer tube replacement?

If the steerer is a French dimensioned one (and I suspect it is) then it's diameter is 25mm. Current Eng/ISO threaded steerers are 1", or 25.4mm. So some significant enlargening of the crown's socket will be needed. Andy

I have a very nice Trek fork from a 1979 900 model. The 900 was Trek's best bike at the time, the fork is made from Columbus SP. The frame was 25 inch and will fit 27 inch wheel, so this might fit perfectly. I'd be willing to send it to you for s&h.

My question is if your frame is French tubing with French threading. Can you determine the tubing type and measure the steerer for both length and diameter? Can you post a picture of the Reynolds 531 decal?

I believe Chris Kvale has some NOS French steerer tubes 260 mm long-$25. They are around. Or generic 4130 25 mm od.

The steerers are more available than crowns with a 25.0 steerer hole. Too critical of a joint to trust a shim there.

I have some French steerers myself, which I've had since the early '80s and haven't found a crown for them in all that time. Not that I've been looking exactly...

Anyone got any French crowns to sell me?

Mark B in Seattle

I would ask if you really want to make a French fork, but I guess there some demand for replacements. I imagine there are piles of French crowns rusting away in France somewhere.

Exactly, no one wants a French thread fork because it's better (it's not), it would only be for someone trying to do a credible restoration of a vintage bike with the fork missing or totaled. A bike where an English headset or 22.2 stem wouldn't be allowable. In my size (~65 cm), replacement forks that fit the bill are very rare, so if I had the crown I might build a fork, it's easy for me.

Don't ask about the logic of it, it's not logical. Vintage bike nuts are whack (I can say that because I are one.)

Mark B

Two words: flat plate crown.

I never could count

But really, there are places that do laser cutting for very little money. If it was good enough for Faliero Masi ...

Here is an example of a flat rate fork crown I had laser cut in Ukraine for the Utility bikes we make for our charity project. The SS cross was laser cut too. The theory was that it might deter a thief a little or at least make him feel a bit guilty when riding it.

Assembling the two plates into a fork crown was a little more complicated then I originally imagined. It is easy to get the plates twisted on each other or crooked to the crown. I eventually made a tool to hold them while they were brazed to the steerer. I also used some 0.058" wall tubing as a spacer and of course had to make a crown race on my lathe.

https://cimg0.ibsrv.net/gimg/bikefor...acd194993.jpeg

Doug, that looks nice. It looks like an oval blade, how did you lay out the hole for it?

The blades are round. Got them from True Temper before they stopped making them. Round blades makes it easy to put the small end in the middle of the dropouts because they can be turned in the crown until the ends match up with the center of the dropouts when they are all held in a fixture. I drew on paper the design I wanted and handed it off to the CAD guy at the laser cutting company.

I've included a picture of the tool I use to keep the 2 flat plates in position while I spot braze them together. I discovered how easy it was for them to get out of kilter unless they were rigidly held.

I also had flat plates made for conventional oval blades. Kirk Pacenti designed the for me and I have them laser cut in Ukraine. In this case they machined the socket in the top plate. If there was any interest, I can have more made. Like the cross on the fork of the Messenger bikes, some kind of design could be laser cut and brazed to the top plate to add a bit of marketing or pizzazz to a fork.

If someone wanted to use a French steerer, the same 2 plates could be used and the center spacer thing could be machined on a lathe to the correct diameters. It wouldn't be as easy to do because the spacer on these crowns can be easily made out of 0.058" wall tubing (which is commonly available).

https://cimg7.ibsrv.net/gimg/bikefor...fc9f8ee9d.jpeg
https://cimg1.ibsrv.net/gimg/bikefor...0d6db61dc.jpeg

Thanks, Doug

If you do a search on eBay for ‘Mondia’ in Cycling Equipment you’ll find quite a few forks with French threads....
NOS forks that are chromed!
Like this one: https://www.ebay.com/itm/333593511708

I found a nice replacement fork for my Mondia because the threads on the old fork’s steerer tube came up too short for the Hdset (not enough threads).

Sorry for the long delay - I needed a good time to get greasy and fussy. The thread on the steering tube is 1mm pitch, on 25mm OD, 22.2mm ID, but the headset is stamped 1 X 24. This explains the stripped threads. The steering tube is 8 7/8" long, and the fork offset is about 2". The 531 decals are under paint. A scrounged fork would really be in character for saving my faithful old friend. I even had a roommate who imported a really good Trek in '84.