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Old 08-31-08, 02:23 AM   #1
bjtesch
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is fork straightening possible?

I have a steel frame from about late 1980's, with steel fork and integral crown. I had a problem with an obstacle that shortened my wheelbase a little bit. I'm wondering if a fork can be straightened or is it likely damaged too much?

Also if I needed to swap in a new fork, is it feasible to remove the headset races from the old fork and put them on the new fork? It has a standard DuraAce threaded headset.

I haven't confirmed that there is no frame damage yet but I'll do that before I proceed with this project.
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Old 08-31-08, 04:10 AM   #2
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I'm wondering if a fork can be straightened ..?
That'd depend on who'd you ask. Back in the days forks were delivered straight, and the frame builder would bend them to the shape and geometry he wanted. Rear stays are routinely bent to make room for wider hubs.
Personally I'm inclined to scrap bent forks. I find that for my needs forks are so easy to come by that I don't bother messing about with bent ones, unless I'm looking for an improvised trueing stand.

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...or is it likely damaged too much?
That would vary from case to case, there's no general answer.

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..if I needed to swap in a new fork, is it feasible to remove the headset races from the old fork?
Sure, there are nice extractor tools for it, but otherwise some carefully applied force courtesy of a hammer and some expendable tools(knife, screwdriver) will do the job.
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....and put them on the new fork?
Usually, yes. There are two 1-inch standards, IS and JIS, and that can sometimes trip you up. Measure carefully, or bring the old fork when you go shopping for the new.
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It has a standard DuraAce threaded headset.
No help there, Last D-A headset I came across was for an JIS one-inch headtube.

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I haven't confirmed that there is no frame damage yet but I'll do that before I proceed with this project.
That'd be sensible. There are ways to deal with ovalized headtubes, but I've never managed to untwist a twisted frame. If the wheels arent in the same plane riding characteristics becomes really interesting.
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Old 08-31-08, 06:55 AM   #3
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Originally Posted by bjtesch View Post
I have a steel frame from about late 1980's, with steel fork and integral crown. I had a problem with an obstacle that shortened my wheelbase a little bit. I'm wondering if a fork can be straightened or is it likely damaged too much?

Also if I needed to swap in a new fork, is it feasible to remove the headset races from the old fork and put them on the new fork? It has a standard DuraAce threaded headset.

I haven't confirmed that there is no frame damage yet but I'll do that before I proceed with this project.
I've had frame realignments done a few times over the years, and I can tell you a good frame technician can straighten bent forks and frames. Not extreme bends, but some pretty significant bends. Find an expert and show him, let him tell you if it can or can't be done. If you have a local framebuilder, that is probably the right person.

I think it's definitely feasible to swap an old headset from one frame to another, as long as the ID of the head tube top, head tube bottom match frame to frame, the OD of the crown race seat match, and the steer tube length match.
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Old 08-31-08, 04:10 PM   #4
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The frame in question is a Tesch 101, which came with custom paint. If I put on a new steel fork I'd have to paint it to match, which is why I was thinking I need to straighten the original fork or swap in a carbon fork so I can keep riding it, and save the original fork in case I eventually want to sell the frame to a collector.

I'll see if I can find some local frame experts. Straightening the original fork seems to be the most direct solution, if possible. I have 2 frames almost identical so I just ride the other bike these days. I have not felt like messing with the damaged bike until now. The fork isn't bent a lot, and I think I can compare the wheelbases of the 2 bikes to get a good idea of how much. I really doubt there is damage to anything but the original fork but I'm trying to figure out how to get some accurate measurements of the head angle so I can confirm that.
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Old 08-31-08, 05:33 PM   #5
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I'd say it really depends upon how far off it is. If the adjustment is less than 2cm, I'd say it's OK to bend it back. If it's more, I'd worry about the amount of stress needed. You see, in order for the fork to take a permanent bend in the first place, you have to exceed the material's yield-strength. Then to fix it, you have to exceed it's yield-strength a 2nd time in the opposite direction, very scary.

Also in general, the stronger the alloy, the closer yield-strength comes to ultimate-strength. By the time you apply enough force to make a bend stick, it's also very close to breaking.
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Old 08-31-08, 06:57 PM   #6
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Just to add to Danno's post which I agree with every bit of. To avoid doing MORE damage when bending back even a small bend you'll want to make up a saddle from a hardwood block so the shape of the tube is protected as you bend it back. Otherwise you're risking a kink forming in the tube as you bend it. If that happens it trash time.

Again a couple of cm, no problem. Something that looks like it got run over by a tank? Toss it.

Check the alignment at the brazed joints around the crown as well. Any sign of misalignment there means the joint has broken. Again it's either time for a frame guy or good torch man to rebraze or toss it into the dumpster.
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