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Old 02-14-12, 01:41 PM   #1
supafast213
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Slightly bent steel fork

I always suspected that my old Fuji had a slightly bent fork. However, when I converted the bike to 700c, I completely rebuilt the front wheel (my first wheel build).
I have never been able to get the front wheel to align with the center brake screw. I tried redishing the wheel to center but It was never quite right. I recently acquired a new set of decent wheels and decided to "chuck" em up in the Fuji. This is what I found....


The next shot is with the wheel reversed.


I believe that this is being discussed in another thread, which gave me the idea to test. My theory is that the LH fork is pulled back slightly. I took a look at the Park Tool sight and I get the general idea of what I'm up against. I was wondering if anyone had a tried and true method for pulling fork legs back into alignment.
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Old 02-14-12, 03:04 PM   #2
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There are alignment tools that will check for and correct fork and frame misalignment. The Park FFG-2 is one such tool and any good bike shop should have one but it's too expensive for a one time home user to bother with. Find a bike shop with the Park or similar tool and let them do the job for you.

BTW, caliper brake front wheels are not "dished" (i.e. have the rim offset between the hub flanges) like most rear wheels but should be symetrical and the rim centered between the flanges. If you had to build the rim off center, the fork is indeed not aligned properly.
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Old 02-14-12, 03:16 PM   #3
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I've seen this happen when the axle dropouts were not equidistant from the crown. In other words, the axle was not parallel with the ground causing the wheel to lean to one side. If this is the problem with your bike I do not know the best way to fix it. You may be able to center the wheel in the fork and then tighten the axle in the fork with the skewer or axle nuts.
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Old 02-14-12, 03:22 PM   #4
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Find a bikeshop with one of Park's fork alignment reference tools ,
and get it properly bent back into shape.

One blade may precede the other , or be further off the centerline than the other ,

no way to really dial it in until you have a zero to reference from.. a baseline.
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Old 02-14-12, 03:32 PM   #5
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As my bicycle guru friend pointed out today, it is best not to assume that any reference point is correct in this repair. The Park tool designed for this job puts two planes in the center of the dropouts. If these two surfaces are coplanar, the forks should be correct.




I would like to replicate this tool. Does anyone have any "homemade" versions of it?

Hillrider, You are correct. The tool costs more than my needs dictate. Also, sorry for the misused term for centering the wheel. I refer to "dishing" as any movement of the rim relative to the hub.

Last edited by supafast213; 02-14-12 at 03:36 PM. Reason: ps to hill rider
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Old 02-14-12, 03:36 PM   #6
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Could the OP just file the axle dropout a tiny bit to allow the tire to move over a tad? I know, he should get it measured and properly repaired, but it seems like it should work just fine in a pinch, especially if the bike isn't a high end bike worthy of putting bigger dollars into.

just a thought.
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Old 02-14-12, 05:09 PM   #7
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The Park FFG-2 tool can put the fork dropouts into alignment, but it doesn't align them relative to the plane of the seat tube. And it can't tell you if the fork blades provide the right trail offset which happens in a front end collision. For major front end damage, we'd re-align the frame and order a new fork. But for minor bends, we had a jig down stairs on a table. It was beefy chunk of angle iron mounted over the straight end of a table. A very beefy fork mount with QR skewer was welded onto the chunk of angle iron and calibrated for 90 degrees. Markings on the table had lines going through the center axis. So if the steerer tube wasn't aligned, we'd thread one of the tall threaded sleeves onto the outside of the threaded steerer and stick a machined steel rod inside the steerer and bend that steerer to be straight. If the steerer wasn't centered over the fork crown, then we'd use a block of wood with a curve from the side of the fork and tap it firmly to recenter the fork. If the fork rake/trail offset was wrong, we'd flip the fork over so it'd be concave down, reclamp the QR, and there was a rounded block of wood we'd slide under the fork blades that acted as the bending radius. Some firm pressure on the fork crown and the fork blades would bend back usually. If one of the fork blades was ahead of the other, we'd use a small sawed-off wooden boat paddle and insert that under one of the blades and pry gently with the radius block in place. It wasn't a perfect fork alignment jig, but it allowed just about anyone to gain enough leverage to quickly straighten out a tweaked fork back into fairly good alignment.
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Old 02-14-12, 05:35 PM   #8
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Those are the Tip alignment tools,not what I was referring to,
the fork steerer out of the bike..lays in a V,
the reference, a T on the other end, is where the fork tips should be
relative to the steerer tube.


Looks like Park Used to make them 18 years ago, ..though, not now .
( looked at website, asked them ).
maybe too many lawyers to try any more..


V block and an accurate block to lay the fork crown against , to have that horizontal
on a surface table , machined dead flat , and a micrometer to measure
the fork tip axis off the surface of the table is well beyond a bike shops
tool level , maybe a premium priced hand-built frame builder would
have that investment
Italian or German companies make those machine tools for the trade.

Last edited by fietsbob; 02-15-12 at 10:48 PM.
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Old 02-14-12, 05:48 PM   #9
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Those are the Tip alignment tools,not what I was referring to,
the fork steerer out of the bike..lays in a V,
I didn't know Park made a fork alignment jig in the shape of a V. I've known about their lever tools to bend the frame and fork back into place, but these aren't V-shaped. Maybe the fork alignment jig was a Bicycle Research product? If you have a link, that might be interesting for some shops to acquire.
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Old 02-14-12, 05:58 PM   #10
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you didn't get the rest of the idea ,[ NB V blocks are a common machinist's method
to align and hold with a clamp, round tubes .. to say drill a hole straight through it. ]

the fork steerer clamped in the V block holds it down. any normal diameter. within reason.
then in this case there is a rigid T welded onto these tools extending out to where the axle should be.

might be too many lawsuits to do anything to fork..

bicycle research Nope, just small stuff,
do still make the spoke nip crank screwdriver.

other tools >http://www.marchettispa.it/
http://www.starrett.com/
http://www.mitutoyo.com/

Last edited by fietsbob; 02-14-12 at 06:30 PM.
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Old 02-14-12, 06:40 PM   #11
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A few years ago I had a bike shop realign a bent steel fork for $40. I don't know how prices run where you are, but you might find it's affordable to just have a bike shop do it. Couldn't hurt to call around....
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Old 02-14-12, 07:52 PM   #12
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Quote:
Originally Posted by gyozadude View Post
The Park FFG-2 tool can put the fork dropouts into alignment, but it doesn't align them relative to the plane of the seat tube. And it can't tell you if the fork blades provide the right trail offset which happens in a front end collision. For major front end damage, we'd re-align the frame and order a new fork. But for minor bends, we had a jig down stairs on a table. It was beefy chunk of angle iron mounted over the straight end of a table. A very beefy fork mount with QR skewer was welded onto the chunk of angle iron and calibrated for 90 degrees. Markings on the table had lines going through the center axis. So if the steerer tube wasn't aligned, we'd thread one of the tall threaded sleeves onto the outside of the threaded steerer and stick a machined steel rod inside the steerer and bend that steerer to be straight. If the steerer wasn't centered over the fork crown, then we'd use a block of wood with a curve from the side of the fork and tap it firmly to recenter the fork. If the fork rake/trail offset was wrong, we'd flip the fork over so it'd be concave down, reclamp the QR, and there was a rounded block of wood we'd slide under the fork blades that acted as the bending radius. Some firm pressure on the fork crown and the fork blades would bend back usually. If one of the fork blades was ahead of the other, we'd use a small sawed-off wooden boat paddle and insert that under one of the blades and pry gently with the radius block in place. It wasn't a perfect fork alignment jig, but it allowed just about anyone to gain enough leverage to quickly straighten out a tweaked fork back into fairly good alignment.
I would love to see this setup.
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Old 02-15-12, 12:19 AM   #13
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I would love to see this setup.
Unfortunately, that was more than a couple decades ago in a shop long closed. No cheap dig cams back then to take a picture of it. It was beefy, but not too big. The shop owners mounted it to a big workbench in the basement for stability.
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Old 02-15-12, 01:31 AM   #14
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I was wondering if anyone had a tried and true method for pulling fork legs back into alignment.
You have already made a determination of where you think the problem lies. There have been suggestions on how to check where the problem is- but not how to fix it. Go with your gut- get your biggest buddie to help you- buy him a 6 pack of PBR- put a good sturdy wheel in the fork, and twist it around until it's back in alignment. It's a steel fork and will withstand a good amount of twisting without hurtin' it. I'd bet you'd be out about 2 minutes time and a six-pack of beer.

I'm serious.
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Old 02-15-12, 09:00 PM   #15
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You have already made a determination of where you think the problem lies. There have been suggestions on how to check where the problem is- but not how to fix it. Go with your gut- get your biggest buddie to help you- buy him a 6 pack of PBR- put a good sturdy wheel in the fork, and twist it around until it's back in alignment. It's a steel fork and will withstand a good amount of twisting without hurtin' it. I'd bet you'd be out about 2 minutes time and a six-pack of beer.

I'm serious.
I'm seriously considering giving it a good shove in the right direction. Unfortunately, I threw away some **** wheels that would have been perfect for this task. I'm thinking about removing the fork and double checking my guess on a flat surface. I can think of a few ways to straighten the fork once it's off the bike.
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Old 02-17-12, 08:37 PM   #16
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I was screwing around in the garage tonight, so I pulled the fork on the Fuji and tried to get a better look at it's condition. The only flat surface I could find was the stove top. So I took some pics. The paper is there for me to "eyeball" but it wasn't very effective.





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Old 02-18-12, 12:59 AM   #17
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Looks vaguely obscene from that angle.
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Old 02-18-12, 06:20 AM   #18
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did you check to see if the wheel was dished ( centered ) correctly?
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Old 02-18-12, 05:06 PM   #19
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I can't help you with your issue, but it reminds me of a story. I had a rescued-from-the-trash lower end (i.e. soft metal) Bianchi frame, slightly bent with a noticably bent fork. Took it to my LBS run by two brothers who have been in the business for years. One of them took the frame and fork, got out all sorts of big clamp type items which I'd never seen before, clamped the frame, then fork in, started bending until he says "that looks about right". Then measures them with the alignment tools. Everything was lined up perfectly. I was impressed with his ability to align them by sight. He said that back in the steel frame days he'd realigned lots of bent frames.
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Old 02-18-12, 06:57 PM   #20
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did you check to see if the wheel was dished ( centered ) correctly?
The reason that this issue has gone unchecked for several miles is that I was unsure of my wheel building prowess. It wasn't until I used a factory built wheel to test that I was suspect it was a bent fork.
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Old 02-18-12, 08:54 PM   #21
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I was wondering what the big deal was? So what if its a little off. It's not race machine. the other option is finding another fork, a used one maybe.
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Old 02-18-12, 09:34 PM   #22
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I use one of these:

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Old 02-21-12, 08:03 PM   #23
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Well, I went ape sh*t on my fork today with this tool (borrowed from friend for straightening his sons motocross bike subframe)


It was very difficult not to go past the correct bend with this over sized behemoth. I was having trouble with placing the tool on the correct portion of the fork. If i put it at the bend, I affected the lateral and vertical alignment, if I used it near the crown, I only affected the lateral. I finally gave up around "close enough". If I had the park tool dropout alignment gauge, I would have gone for perfection.



I was able to adjust my front brake to a tighter tolerance after adjusting the fork. This will suit me for now.
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Old 03-06-12, 08:42 PM   #24
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Can I highjack this? I have this beautiful 1988 Fuji Tiara with the killer cherry web frame (there are a few floating around on the site, khatful had a thread about his). I have been noticing some bubbles in the paint on top the fork where it joins with the head tube. I crashed and now you can really see it is bent back, though not terrible. My question is not if its bent, but what i can do with it. The paintjob is pretty much irreplaceable and I am really worried about it. It's steel, can I have the lbs bend it back? Local welders? The bike would look terrible without the fork.

http://i1186.photobucket.com/albums/...o/P1010733.jpg
(this is before the crash, I just wanted you to understand the paint situation)
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Old 03-06-12, 09:01 PM   #25
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MiamiJim in #22 has the right shop tool.. seems Park dropped making theirs in he 90s
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