What Causes This Type Of Damage?
 

This bike is on CL in San Francisco and the seller mentioned damage to the steerer and included this photo.. What causes this damage and is it truly repairable?


https://cimg2.ibsrv.net/gimg/bikefor...66cba7d233.png

Overtightened stem expander/wedge? Repair threads, drill a hole at each end of crack to stop the spread, file the edges smooth. Use a taller stem and insert slightly deeper, but remain above any steerer flaring near crown.

Not sure it’s worth it— I would replace the steerer, or even the fork.

What?? Wait!! What is that? I'm agreeing with [MENTION=348133]panzerwagen[/MENTION] that this split is from the stem expander, however, it looks like there are no threads in just that area but are around the rest of the steerer tube. That area also looks to be painted rather than bare metal.

Was this section of the steerer tube indented, which would be why it didn't get threaded and then got painted? Then being indented, cracked when the stem expander was tightened?

Can we get a few more pictures from different angles. This sure is odd.

That's some weird ****.

More importantly.
Do you have a local frame builder who can do the work? Mailing away (and back to you ) will add costs.

What will they charge? Can you buy a Gitane fork for less than the repair?

IIRC I paid $50 Canadian before Covid for similar, but I knew the builder and he knew me and no mailing.

Maybe. But that expander/wedge should be below those threads, not completely above where they start. That silly minimum insertion line is there for that reason. Also, the bottom of the stem being there means it is too high, so a larger than intended maximum bending force (that would push back on the stem bottom when you press down on the bars hitting say a pothole). And that greater than intended bending force is resisted by a shorter lever. The force at the bottom of the stem resisting bending is in proportion to the inverse of the lever length. Say this stem was only inserted 2/3s of the way to to the min insertion line. Well, that's 1 1/2 X the bigger than designed for bending force applied at the weakest part of the steerer.

If that crack is not at the back of the steerer (your picture doesn't give any clues), I'll put on my dunce cap and go sit in the corner.

And second question - any damage to the threads at the top of the steerer? Maybe a little stretching at the back and bending forward at the front like someone tried to wrench the stem forward and bars down? If my presumption in the last post was right, that's what the stem was made to do. The headset locknut and threads under it would not have been happy about it.

French steerer, the HS washer has a matching flat for anti rotation, all normal stuff.

Aside from the crack/split from stem being raised too high. :twitchy:

That is the only photo that the seller is showing. Beaded on the text in the CL listing, the seller was unaware of what and when this happened but apparently he had ridden the bike without issues. Doubt we’ll ever learn what happened but the stem riding way, way too high in the steerer is as good an explanation as any.
Thanks for your responses!

The 'French File' method.

DD

I blame Gitane. Even a stem lowered to hide the Min Insert line will still cause this damage if there are too many threads, like on this fork., It's criminal negligence IMHO. I'm not being hyperbolic, I mean literally criminal. A company should pay a heavy fine for letting this go out, it has caused a lot of pain and suffering over the years. Ensuring each fork has the right number of threads would have increased their costs by what, 50 centimes?

I'm still a fan of threaded steerers when they aren't done by morons, but given there are morons like Gitane in the world, I guess that means we can't have threaded steerers anymore.

The take-away is, you cannot know if your stem is inserted enough until you take the fork out of the frame and see where the streading stops. The Min Insert line, when present (older stems didn't have one) gives a false security if you blindly trust that your fork was not made by morons.

Mark B.

from what I can see (and base guesses on) this criminal negligence (in manufacturing) probably occurred back around 1972-75...so the statue of limitations probably long expired. The builder certainly may have expired, too, not to mention the company.

Then there's the more contemporary negligence of the owner (or shop mechanic) who installed and tightened the stem.

If this is a cheap fork with a seamed steerer: personally I would not bother trying to splice in a replacement steerer.
If it's a 531 fork (say on a TdF) then I would...and check with Bernie Mikkelsen in Alameda for a quote.

Not sure which models/years had this orange color with BCM headlugs...anybody draw a bead on it?

What I find strange is that particular frame looks to have been built specifically for the components; IOW, to be sold as a complete-bike. If true, they'd have specced the HS long before production - and should have known to the millimeter how much threading the fork steerer tube would require based upon the stack height.

I could be totally wrong - but I'm a dancin' foo-ooo-ooo-ooo-ooo-ooo-ooll!

DD

I've seen lots of production bikes where the steerer threading extended far below the upper headset, at least an inch in some cases.

Love me some Zappa!

I think what's going on is the tube maker only wants to make steerers in like 4 or 5 cm increments to reduce the number of SKUs. With quality butted steerers, you have to be careful about shortening them, you might be cutting too much of the butt off. On the other hand, with cheap unbutted steerers where you just shove a plug of thicker pipe up in the bottom of the steerer, I can't think of any excuse for too many threads. You can just as easily make the steerer any length, so why not do it right?.

As a custom builder, I was somewhat fanatical about that, and strived to always have a bare minimum number of threads. Yay for me, I'm so special... ;)
I know we can't expect quite that level of care on mass-produced forks. But even with the lowered expections we have for factory bikes, this current example is still pretty egregious.

Dave Tesch (RIP, great guy) used to have a threading machine that quickly and precisely put threads on finished forks, that he made all the same with extra-long steerers. (Before threadless headsets were invented.) This enabled him to make forks in large batches, and then assign them to frames later as necessary by chopping them to length and threading — just the right amount, natch. It was like a die, but segmented so the pieces came apart after the threads are formed, so it never has to back up. Davidson used to ship him a fork once in a while when we needed to have threads added, because adding threads with a normal die, even a good one (ours was Campy) is dangerous, sometimes it ruins the fork. I was jealous of his machine, but it was very large and expensive. I think he bought it used at an industrial auction; a bike frame building operation his size usually can't afford such a beast, not to buy new anyway. But you know who could afford it? Gitane!

Mark B

Take a peek inside the steerer. Is there a tube seam coincident with the (remarkably linear) split?

This appears to be a Gitane Tour de France, so that's probably a Nervor steerer which goes inside a generic seamed tubing head tube - Gitane allegedly skimped on using 531 head tubes. I would be pondering either (a) having it replaced with a British/ISO steerer and changing the headset or (b) just running a brake cylinder hone down the inside of the steerer to smooth it up and clean out any corrosion, then fitting a Nitto Technomic with a long quill in there, so that the clamping force was well below the damaged area. Or is that an exceptionally bad idea?

It is fairly common for French bikes to have a flat milled on the steer tube with a matching washer, to serve the same function as a slot on most other forks, fitted with a keyed washer. The steer tube is threaded, and the flat milled through the threads prior to painting.
https://cimg1.ibsrv.net/gimg/bikefor...18afd05175.jpgThe damage was caused by a combination of overtightening the stem bolt and setting the stem too high in the steer tube. The expander wedge or cone on the stem should sit below the threaded section of the steer tube.

No, the linear split is due to milled flat for the anti-rotation washer. The split opened at the thinnest point on that milled flat.

Trek had a machine like that as well. Trek spec'ed unthreaded steer tubes from the tubing manufacturers and cut them to length and threaded them as needed. Dave probably got the idea from his time working at Trek before moving to California.

Excuse me, but does this headset/head tube look to be jacked up as well?
https://cimg1.ibsrv.net/gimg/bikefor...6d14d947b0.png

Ice? Looks much like a water pipe rupture due to freezing. I've had a top adjusting nut split on a motorcycle from water ingress and freezing temps.

Yes, but without any measuring, it sure looks to me like a stem at the minimum insertion line would have its expander below the threads.

[MENTION=380471]FBOATSB[/MENTION] The former user used his bars and stem to lever the headset. I asked about the steerer threads in a former post. That (Stronglight looking) headset is a pretty solid unit when wrenched tight. If the locknot was forced and damaged the top of the steerer, some damage would also occur at the top of the headtube. Not as much. There would be less movement there, but the forces would be higher.

If this were my purchase, I'd assemble the bike with fork as is, do a ride and see if, headset and steering excluded, the bike was a keeper. If so, I'd take it to a framebuilder for a patch. Re-threading. General prettying. Then simply use stems with lots of quill inserted.

https://cimg5.ibsrv.net/gimg/bikefor...2c3eec6655.jpg
It will take a lot of sanding to sand that whole length down from 22.2 to 22.0mm though :lol:

I have French replacement chrome-plated CroMo fork. I'll dig it out and take a look. Offered it to a Peugeot guy years ago but he passed.