One Way to Straighten (?) forks...
#1
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From: Thunder Bay, Ontario, Canada - burrrrr!
Bikes: 1958 Rabeneick 120D, 1968 Legnano Gran Premio, 196? Torpado Professional, 2000 Marinoni Piuma
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.
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.
#2
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Joined: Nov 2004
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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.
#3
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.
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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#4
Death fork? Naaaah!!

Joined: Nov 2005
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From: The other Maine, north of RT 2
Bikes: Seriously downsizing.


You must have trained with my old man.
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(looking for a picture and not seeing it? Thank the Photobucket fiasco.PM me and I'll link it up.)
You know it's going to be a good day when the stem and seatpost come right out.
(looking for a picture and not seeing it? Thank the Photobucket fiasco.PM me and I'll link it up.)
#7
aka Tom Reingold




Joined: Jan 2009
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From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
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.
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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Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog
“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author
Please email me rather than PM'ing me. Thanks.
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog
“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author
Please email me rather than PM'ing me. Thanks.
#8
Full Member


Joined: Nov 2010
Posts: 263
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From: Olympia, WA
Bikes: Constant rotation, Currently: 2009 Felt FC, 1999 Stumpjumper, Serotta KOM, Eisentraut Rainbowtraut, Trek 400 commuter
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.
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.
#9
You gonna eat that?
Joined: Sep 2008
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From: Fort Worth, Texas Church of Hopeful Uncertainty
Bikes: 1966 Raleigh DL-1 Tourist, 1973 Schwinn Varsity, 1983 Raleigh Marathon, 1994 Nishiki Sport XRS
#10
Thread Starter
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Joined: Apr 2007
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From: Thunder Bay, Ontario, Canada - burrrrr!
Bikes: 1958 Rabeneick 120D, 1968 Legnano Gran Premio, 196? Torpado Professional, 2000 Marinoni Piuma
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;-)
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;-)
#11
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.
#12
multimodal commuter
Joined: Nov 2006
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From: NJ, NYC, LI
Bikes: 1940s Fothergill, 1959 Allegro Special, 1963? Claud Butler Olympic Sprint, Lambert 'Clubman', 1974 Fuji "the Ace", 1976 Holdsworth 650b conversion rando bike, 1983 Trek 720 tourer, 1984 Counterpoint Opus II, 1993 Basso Gap, 2010 Downtube 8h, and...

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.
#13
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Joined: Oct 2010
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From: Minnesota- the frozen tundra
Bikes: 1977 Raleigh Super Grand Prix, 1976 Gitane Tour de France
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?

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?
#16
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Joined: May 2008
Posts: 10,106
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From: Fredericksburg, Va
Bikes: ? Proteous, '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, 'Litespeed Catalyst'94 Burley Duet, 97 Specialized RockHopper, 2010 Langster
Think I could fix this?


#19
I would speculate that "fork" is correct - after all, the legs are merely tines - not additional forks!
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#20
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Joined: Apr 2005
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From: Ann Arbor, MI
Bikes: 1980 Masi, 1984 Mondonico, 1984 Trek 610, 1980 Woodrup Giro, 2005 Mondonico Futura Leggera ELOS, 1967 PX10E, 1971 Peugeot UO-8
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.
#21
Senior Member

Joined: Apr 2005
Posts: 17,196
Likes: 761
From: Ann Arbor, MI
Bikes: 1980 Masi, 1984 Mondonico, 1984 Trek 610, 1980 Woodrup Giro, 2005 Mondonico Futura Leggera ELOS, 1967 PX10E, 1971 Peugeot UO-8
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?

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?
#22
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Joined: Mar 2008
Posts: 5,630
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From: Rhode Island (an obscure suburb of Connecticut)
Bikes: one of each
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".
Last edited by sailorbenjamin; 11-30-10 at 05:08 PM.
#23
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Joined: Mar 2008
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From: Rhode Island (an obscure suburb of Connecticut)
Bikes: one of each
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.
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.
#24
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.
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.
#25
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.
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.





