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Bent fork?

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Old 02-11-18, 08:13 PM
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Hatchet
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Bent fork?

Iíve got a bike that has something wrong with the headset, and/or the forks. When just walking the bike by holding the seat, the front wheel wants to flop to the non-drive side. When I hang the bike up by the back wheel, the front wheel slopes to one side. Additionally, the wheel doesnít bisect the space between the two fork blades evenly.

I am teaching myself bike mechanics, so Iíd like to fix the this issue as a learning experience.

I have already looked over the forks and donít see chips in the paint that would indicate any trauma. I also looked down the length of the fork blades and donít see anything obvious - but I feel that I might be missing something.

For a problem like this, what steps should be taken to (a) diagnose and then (b) resolve this issue?

I am also wondering what is happening, on a mechanical level, to the fork/headset.

Thanks.
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Old 02-11-18, 08:36 PM
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It is impossible to tell from your photos.

You have both more brake cable on the bike right (photo left), as well as the wheel being offset to the bike right (photo left). That would give you more weight on that side and cause the wheel to turn when hanging.

The first thing I'd do is to sit the bike on the ground. Loosen the front wheel axle nuts, and make sure the wheel is sitting squarely in the fork dropouts, then retighten. Does the wheel remain offset?

Next, remove the wheel, and flip it around the other way Right <==> Left, and re-install. Where is the wheel offset? If the wheel remains offset on the same side (bike right), then it is likely a fork problem. On the other hand, if the wheel becomes offset to the other side (bike left), then it is a wheel problem.

If the problem follows the wheel... thus, a dishing problem of the front wheel, it is a simple remedy on a truing stand.
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Old 02-11-18, 08:52 PM
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Originally Posted by CliffordK View Post
It is impossible to tell from your photos.

You have both more brake cable on the bike right (photo left), as well as the wheel being offset to the bike right (photo left). That would give you more weight on that side and cause the wheel to turn when hanging.

The first thing I'd do is to sit the bike on the ground. Loosen the front wheel axle nuts, and make sure the wheel is sitting squarely in the fork dropouts, then retighten. Does the wheel remain offset?

Next, remove the wheel, and flip it around the other way Right <==> Left, and re-install. Where is the wheel offset? If the wheel remains offset on the same side (bike right), then it is likely a fork problem. On the other hand, if the wheel becomes offset to the other side (bike left), then it is a wheel problem.

If the problem follows the wheel... thus, a dishing problem of the front wheel, it is a simple remedy on a truing stand.
Thanks for those tips. I'll try those ideas and see what happens.
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Old 02-11-18, 08:58 PM
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On a bike of that quality, you may need to manually center the wheel. The dropouts aren't carefully machined. Some bike of that type were also meant to be used with safety tabs that fit in holes above the dropouts.
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Old 02-11-18, 09:13 PM
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It looks to me like the left blade in pic is pushed in where the tire is, like it fell on something.
The right one is perfectly straight. I have a really good eye for this stuff.
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Old 02-12-18, 11:20 AM
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Its a cheap old bike, don't sweat it, you wont like the bike shop labor cost to make it any better..
1) you have to take it out of the bike, not just take a picture.. bending can be in several axis; right, left, fore, and aft.. (X2) from the center line..

But, yea it is a good place to start learning basic bike mechanics.






...

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Old 02-12-18, 11:27 AM
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I also clearly see a bent "dropout" or "fork end".
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Old 02-12-18, 01:08 PM
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Originally Posted by Kontact View Post
On a bike of that quality, you may need to manually center the wheel. The dropouts aren't carefully machined. Some bike of that type were also meant to be used with safety tabs that fit in holes above the dropouts.
Yes, this bike does have the safety tabs you describe and both are seated properly.
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Old 02-12-18, 01:17 PM
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Originally Posted by GamblerGORD53 View Post
It looks to me like the left blade in pic is pushed in where the tire is, like it fell on something.
The right one is perfectly straight. I have a really good eye for this stuff.
Now that you mention it, I think I see the bend. You are talking about the fork blade on the left side of the picture, correct? The bend is in line with the top of the tire, right?

How would you go about fixing that?
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Old 02-12-18, 03:06 PM
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As I said #1 take it out of the bike.. Park made a Shop tool you clamp the fork steerer into. and the tool into a bench vise..

It has a reference piece in the tip.. with that reference,suggesting which way, & which one is out of alignment ,
the steel blade is physically bent, with enough force in the appropriate direction.

then re checked with that reference tool ..
That is How I worked with a used fork I bought for a bike I have had on hand for 30 years, since....


here is what that tool looks like Park Tools Fork alignment gauges






...

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Old 02-12-18, 04:05 PM
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Originally Posted by Hatchet View Post
Now that you mention it, I think I see the bend. You are talking about the fork blade on the left side of the picture, correct? The bend is in line with the top of the tire, right?

How would you go about fixing that?
Hi Hatchet. Since you list your location as Buffalo, NY, are you near this bike shop on Ellicot Street? https://gobikebuffalo.org/

This might be your best local source for the help you need with your fork. Simple fix, perfection not required considering the subject bicycle, simple tools.
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Old 02-13-18, 12:04 PM
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Originally Posted by FBOATSB View Post
Hi Hatchet. Since you list your location as Buffalo, NY, are you near this bike shop on Ellicot Street? https://gobikebuffalo.org/

This might be your best local source for the help you need with your fork. Simple fix, perfection not required considering the subject bicycle, simple tools.
Thanks for the tip. I will check them out.
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Old 02-13-18, 01:03 PM
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Looking at the last picture, I don't think one blade is "pushed in". I think both blades are bent to the right, like a parallelogram. Which would explain everything you're seeing.

FYI, in the normal scheme of "bike mechanics", this kind of thing doesn't happen. A nice chromoly fork would likely break before it would bend as you see here. There are limitations to what can be learned trying to fix cheap bikes with soft steel parts.
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Old 03-11-18, 07:45 PM
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Thanks to everyone who offered suggestions for this question I had. This is a great community!

In the end, what worked for me was following the advice here:
https://www.bikeforums.net/newreply....ply&p=20164445

Specifically:
" If the fork is only bent to the side, the correction must be to the side to which the rider must lean when riding no-hands. This bend can be done carefully by bending one blade at a time.

Lay the bicycle on its side, front wheel removed. Place the rubber-soled foot inside the crown of the fork and pull the upper blade until the gap at the fork end increases by a couple of millimeters. This should be measured. With the foot in the same place, pull the other fork blade until the original spacing is restored. Ride the bicycle and assess the difference. Repeat if necessary. This must be done with a strong arm and a bit of skill but it is simple.

If you have a non-steel bicycle, buy a new fork."
By slowly and carefully bending the forks and re-testing, I was able to dramatically reduce the effects of the previously damage.

Thanks again!
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Old 03-12-18, 02:44 AM
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One of my bikes did exactly the same. Wheel flopping to the non drive side. Impossible to ride hands free. Optically everything looked fine. I just continued to ride it and after some 300 km it just went away. No whell flopping any more and hands free riding works fine now.

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Old 03-12-18, 02:59 AM
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Originally Posted by Kovkov View Post
One of my bikes did exactly the same. Wheel flopping to the non drive side. Impossible to ride hands free. Optically everything looked fine. I just continued to ride it and after some 300 km it just went away. No whell flopping any more and hands free riding works fine now.
Probably because you subconsciously adjusted your body position to compensate.
Have a friend ride behind you and see if your back looks crooked.
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Old 03-12-18, 03:36 AM
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Originally Posted by xenologer View Post
Probably because you subconsciously adjusted your body position to compensate.
Have a friend ride behind you and see if your back looks crooked.
Don't think so, because the wheel doesen't flop any more while walking the bike or hanging it somewhere.
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Old 03-12-18, 05:12 AM
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Bikes aren't alive, they can't heal or recover from problems on their own.
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Old 03-12-18, 07:13 AM
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Originally Posted by xenologer View Post
Bikes aren't alive, they can't heal or recover from problems on their own.
I know, but i didn't to anything except riding it.
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