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One Way to Straighten (?) forks...

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One Way to Straighten (?) forks...

Old 11-30-10, 04:29 AM
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One Way to Straighten (?) forks...

I have been having trouble straightening out a set of bent forks on my Bottecchia Special. It does, however, look like my troubles are over....

Looking at how the other guy does it makes me wonder if I am wasting my time with fork gauges, measuring and all that fancy stuff.

All I gotta do is drive over my bicycle, and, voila, good bike.
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Old 11-30-10, 09:47 AM
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It reminds me of time a buddy and myself had cycled on a trip to visit a friend. Fifty miles from home and my friend turns his head to look at a pretty girl. Bam! He rides right into the back end of a parked car and bends his reynolds 531 forks. Fortunately, we were close to the our friend's place. When we got there, we made do with the only tools he had at hand. We removed the front caliper, front wheel and lay the bicyle down, with one 2x4 under the head tube and another under the fork bades, just below the bend. A 3rd 2x4 was placed on the upper blades, below the crown and just above the bend. Then we hit the 2x4 with a sledgehammer. Voila, he rode it home, without any adverse handling problems. At home, I made some fine adjustments and he was still riding it several years later, when he moved to Australia and we lost track of each other. You just have to know how to calibrate your sledgehammer.
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Old 11-30-10, 09:55 AM
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I am sure there are many ways to do it, but I've had good luck applying force with a car jack through the axle (in the exact opposite way that it was originally bent).

The method allows you to apply force iteratively, just a little, then a little more, until it's right.
The u-bolts hold the steerer steady without deforming it, and the wood averts putting any flats on the threads.

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Old 11-30-10, 10:03 AM
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Originally Posted by T-Mar
You just have to know how to calibrate your sledgehammer.


You must have trained with my old man.

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Old 11-30-10, 10:09 AM
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Originally Posted by auchencrow
I've had good luck applying force with a car jack through the axle
Great setup!
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Old 11-30-10, 10:17 AM
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Nothing wrong with doing things primitively sometimes. Ive used a sledge hammer on more than one occasion, works great!
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Old 11-30-10, 10:55 AM
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My mother saw a wheel-less UO-8 on the ground under a highway. She picked it up and gave it to me. The front end was bent in the classic front-end collision way, i.e. the downtube and seattube were bent so that the headtube was too vertical.

I straightened it in the way my bosses at the bike shop taught me. This bike shop had a tendency to buy a minimum of tools.

- We took a long stiff solid (i.e. not hollow) bar and stuck it between two brick buildings. (This was in Manhattan, NYC.)
- Stick the head tube through the bar. Keep the headset cups in the head tube, to prevent distortion at the ends.
- Using the frame itself as a lever, bend the frame.

It worked, though I didn't bend it quite enough, resulting in a slightly too steep head angle, which was OK. Unfortunately, the head tube was also twisted, so the bike had a slight tendency to pull to one side. I was able to ride it no-hands, so the tendency was very slight.

I rode this bike as my commuter for years.
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Old 11-30-10, 11:04 AM
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Originally Posted by noglider
My mother saw a wheel-less UO-8 on the ground under a highway. She picked it up and gave it to me. The front end was bent in the classic front-end collision way, i.e. the downtube and seattube were bent so that the headtube was too vertical.

I straightened it in the way my bosses at the bike shop taught me. This bike shop had a tendency to buy a minimum of tools.

- We took a long stiff solid (i.e. not hollow) bar and stuck it between two brick buildings. (This was in Manhattan, NYC.)
- Stick the head tube through the bar. Keep the headset cups in the head tube, to prevent distortion at the ends.
- Using the frame itself as a lever, bend the frame.

It worked, though I didn't bend it quite enough, resulting in a slightly too steep head angle, which was OK. Unfortunately, the head tube was also twisted, so the bike had a slight tendency to pull to one side. I was able to ride it no-hands, so the tendency was very slight.

I rode this bike as my commuter for years.
Nice, I have a uo-8 that matches that description, glad i looked at this thread, I may just try this out when I get home for winter break.
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Old 11-30-10, 11:25 AM
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Old 11-30-10, 11:52 AM
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Honestly, yesterday I fussed and fussed with a fork set, seeking perfection in alignment. No luck!

It turned out that the fork was made improperly, right from the start. One fork was 2mm longer than the other. Once the distances were matched, things looked much better. I plan to assemble the bicycle and test ride it in the next couple of days, weather permitting.



I am really glad that I presented this thread. Long have I toyed with the idea of building up a fork straightening jig. Some of the ideas I see here are inspiring. If anyone else has frame or fork straightening home made tool ideas, I would like to see them. And remember, the run over your bike with your car is already taken;-)
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Old 11-30-10, 11:53 AM
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I guess it could be argued that a bike suffers some loss of efficiency when it isn't straight. Alignment is a bit like a haircut. You can go without, do it your self or treat yourself to professional service and notice an immediate improvement if it was really needed.
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Old 11-30-10, 12:16 PM
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Originally Posted by ftwelder
I guess it could be argued that a bike suffers some loss of efficiency when it isn't straight. Alignment is a bit like a haircut. You can go without, do it your self or treat yourself to professional service and notice an immediate improvement if it was really needed.


Yeah, but when it comes to haircuts, I have total confidence the professional can do a better job than I. With bicycles, I'm not so sure-- mainly because once upon a time, when I knew far less than I know now, I was a bicycle professional.
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Old 11-30-10, 01:43 PM
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I've ridden hundreds of miles on my Raleigh with a bent fork and honestly it rides beautifully but it does bother me a bit to look at though.



My only concern is the strength of the fork after bending it back and I have to admit that I don't know how they're assembled, is the structural integrity a concern after bending it back? I'm guessing it must not be seeing as how so many of you do this.

Other than appearance and handling (which I'm used to) is there really anything to worry about with my fork as it is in the pic I posted?
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Old 11-30-10, 02:05 PM
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On a Nuvolari Corsa Tartaruga that fork is a "feature".
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Old 11-30-10, 02:06 PM
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It's amazing what the human body can adapt to, when given a chance. Look at that super slack frame that Eddy Merckx built for Steve Bauer.
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Old 11-30-10, 02:43 PM
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Think I could fix this?
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Old 11-30-10, 02:49 PM
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Fork, forks and fork set have been used here to describe the same thing. Which is correct? I've always called a fork a fork, but what do I know?
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Old 11-30-10, 03:12 PM
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Originally Posted by SJX426
Think I could fix this?
Looks like you have nothing to lose!
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Old 11-30-10, 03:14 PM
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Originally Posted by Grand Bois
Fork, forks and fork set have been used here to describe the same thing. Which is correct? I've always called a fork a fork, but what do I know?
I would speculate that "fork" is correct - after all, the legs are merely tines - not additional forks!
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Old 11-30-10, 03:29 PM
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Originally Posted by T-Mar
It reminds me of time a buddy and myself had cycled on a trip to visit a friend. Fifty miles from home and my friend turns his head to look at a pretty girl. Bam! He rides right into the back end of a parked car and bends his reynolds 531 forks. Fortunately, we were close to the our friend's place. When we got there, we made do with the only tools he had at hand. We removed the front caliper, front wheel and lay the bicyle down, with one 2x4 under the head tube and another under the fork bades, just below the bend. A 3rd 2x4 was placed on the upper blades, below the crown and just above the bend. Then we hit the 2x4 with a sledgehammer. Voila, he rode it home, without any adverse handling problems. At home, I made some fine adjustments and he was still riding it several years later, when he moved to Australia and we lost track of each other. You just have to know how to calibrate your sledgehammer.
I'm thinking of doing this with a rubber mallet and some non-anodized Nisi rims, to get them more rideable.
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Old 11-30-10, 03:36 PM
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Originally Posted by FORDSVTPARTS
I've ridden hundreds of miles on my Raleigh with a bent fork and honestly it rides beautifully but it does bother me a bit to look at though.



My only concern is the strength of the fork after bending it back and I have to admit that I don't know how they're assembled, is the structural integrity a concern after bending it back? I'm guessing it must not be seeing as how so many of you do this.

Other than appearance and handling (which I'm used to) is there really anything to worry about with my fork as it is in the pic I posted?
It may have to do with construction, but I'm sure it has something to do with materials. Steels with less strength (1020 or other lower-carbon steels) have more ductility, i.e. they can be bent into different shapes more times before they start to fatigue. With a UO-8 or Raleigh Grand Prix, I suspect you can make corrections that would not be advisable with stainless 953 or some other modern super-alloys.
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Old 11-30-10, 05:03 PM
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Originally Posted by Grand Bois
Fork, forks and fork set have been used here to describe the same thing. Which is correct? I've always called a fork a fork, but what do I know?
Those 3 tined ones that they have at fancy restaraunts my wife calls "threeks" I guess what we ride on is "twoks" Maybe the latin for two, "bi" would be better- "bike".

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Old 11-30-10, 05:07 PM
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I once did a passable job by sitting on the floor in front of the bike with one foot on each pedal and pulling really hard. I took some careful measurements before and along the way.
I had a nearly identical bike to compare it too and it rode pretty much the same afterwards. Before, it rode like a real dog and I couldn't figure it out. It was a subtle bend. Maybe a couple of CMs back and 1 CM to the left. I think the left hand bend was the bigger issue as far as the "doggy" feel as it forces you to ride with the wheel dragging a little sideways to compensate.
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Old 11-30-10, 05:09 PM
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Originally Posted by Road Fan
It may have to do with construction, but I'm sure it has something to do with materials. Steels with less strength (1020 or other lower-carbon steels) have more ductility, i.e. they can be bent into different shapes more times before they start to fatigue. With a UO-8 or Raleigh Grand Prix, I suspect you can make corrections that would not be advisable with stainless 953 or some other modern super-alloys.
Exactly

If your legs bent more than the crown the material is butter and could be adjusted with no worries. I don't push a bent crown around too much.
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Old 11-30-10, 05:21 PM
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It seems like most people call a fork "forks", but I think they're wrong. I see a lot of references to "front forks", too. I don't know what to make of that one.

If you slide a 6' steel tube over the steerer and clamp the fork in a bench vise with some wood blocks, you'll have no trouble bending a fork. I added rake to this fork that way. The only problem was that the chrome popped off at the bend, so I had to paint it.

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