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EDIT/UPDATE: I've removed the fork and don't see any sign on impact/damage. Mabye folks on here can spot something that I can't? I think I'll put a new fork on, as I don't see any signs of damage to headset or frame. Still baffled as to how it got so bent. I feel like I would have noticed this last year when I built it up..

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I rebuilt this Peugeot last year with modern drive train. Never really rode it and had it stored in the basement - I've gotten it out recently and somethings seems off.. The steering is very twitchy, and I'm not at all able to ride with no hands without promptly tipping.

Visually, the fork appears to be sitting in a far more relaxed position. I have been reading about trail and rake but can't totally wrap my head around it.

Whats going on here? Is my fork bent or is something else out of wack? I've looked up other images of the same frame model and noted that mine definitely seems off.

Picture below:

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gamgam
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    The fork does look a little bent but I can't say confidently as it could just be the camera angle. – whatsisname May 08 '20 at 05:28
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    Money on it the fork is bent. 1990's bike has a road like geometry with steep headtube angles. Wonder if someone bent the fork in a naive attempt to replicate the slacker head tube angle of modern bikes. – mattnz May 08 '20 at 05:33
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    In my opinion it's more "i'm surprised it's still in one piece" than "a little bent". 90s MTBs certainly didn't look like that as new. – ojs May 08 '20 at 06:39
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    Stop riding that bike and at least get a new fork. That one's dangerous and may snap. – Carel May 08 '20 at 07:30
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    Do you mind if we ask about the fork's history? It looks very far out of alignment. If it was the original fork, it couldn't have come like that out of the factory. It most likely got that way in an accident, and that would have distorted the frame as well, i.e. it would bend and/or buckle the head tube and/or seat tube, and possibly others. If you buckled a frame tube like that, it is likely to develop a stress fracture soon after. Unless it already has a fracture and you just haven't seen it yet. – Weiwen Ng May 08 '20 at 19:26
  • @WeiwenNg yeah its unusual damage. I'd guess either someone's driven over the fork while its disassembled, or perhaps a previous owner tried to make a lowrider-style bike. I can't see how this bend would occur while riding, unless it was a frontal impact while the fork was rotated 180 degrees? – Criggie May 08 '20 at 21:12
  • I don't know too much about the history - got the frame for next to nothing via craigslist. It seemed fine to me so I went a head and built it up, then kind of put the bike away and forgot about it. Took it out this spring, thought it looked weird, then pedalled it around and definitely knew something was up. Definitely no damage happened while the frame has been in my possession. I must have just not noticed this when I first picked it up used. – gamgam May 09 '20 at 00:05
  • I'm going to remove the fork and headset and inspect further. Will start looking around for a replacement fork - or just transfer this drive train over to a new build. – gamgam May 09 '20 at 00:07
  • It could be simply a matter of too much weight being placed on the bike. – Daniel R Hicks May 09 '20 at 01:21

1 Answers1

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Short answer - your fork is stuffed. Stop riding it.

Longer answer - Here's your bike with the main lines drawn on top

enter image description here

And compare that with this approximate equivalent Peugeot bike. Spot the differences and compare with my list below...

enter image description here

  1. Headtube angle is steeper on your bike - closer to vertical

  2. Negative trail -

    • A line drawn straight down from your front hub hits the ground at a point. This is where the tyre touches the ground.
    • A line drawn down your head tube center line hits the ground after the first line.
    • This difference is called trail, because the tyre's contact patch "trails" behind the head tube's axis. Normally, the larger the trail, the more stable your ride is and the more effort it takes to turn. The trail is what helps a bike go straight by default.
    • Your bike doesn't have positive trail... it has negative trail, or "lead" if you like. Your bike's head tube angle is continuously pushing the front wheel to a side and you have to actively correct this.

  3. Additionally, notice the top tube slopes down. That was not done on MTBs where the top tube was horizontal or sloped up to the head tube. Since the fork is stepped forward at the end, the front is now lower. As a compromise, someone has fitted a small A bar from a kid's bike into the quill stem. This weird set of angles will also compromise handling - you've effectively got 20+ centimetres of stem and the handlebars are noticeably higher than your saddle.

Upshot - you're riding a clown bike that is trying to murder you and may fail at any moment with little to no warning.

The fork is your problem - it needs replacing outright. Once that's done, the existing wheel and brakes should fit up normally. I'd strongly suggest getting a flat bar not that double-stack - once the fork's fixed then the extra height will be more of a hinderance and you won't want to be sitting up like a dutch bike with your arms straight forward.

Do check the headset bearings too - there's a chance they've been damaged.

There appears to be too much bend there for a safe un-bending. Steel is nicely flexible but it has bend limits, and you've likely exceeded them with that level of distortion. If you continue to ride this, the fork is being extra-stressed in the back under the headtube, and this is where it will fail first.

Please ride safe bikes. Right now, this is not a safe bike. This bike can be safe again, with work.

Criggie
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    Thank you! you've confirmed exactly what I suspected. I only peddled it around the block and knew something was off and haven't ridden it since. – gamgam May 08 '20 at 15:04
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    Please check my update with more photos - Does it look like there is any damage done to headtube/headset? – gamgam May 09 '20 at 01:58
  • @gamgam from the photos it looks okay, but the tell-tale is rust. Notice the patches of rust on the rear of the fork (outside of the bend at steerer, and at the two "shoulders") and you can tell something's wrong there. Look inside the head tube and all around, under a bright light, for patterns and clusters of rust marks. You need a replacement rigid 26" fork, with cantilever/vbrake bosses, and a threadded 1" steerer. Avoid any suspension forks. Up to you if you want to replace the headset - give them a good clean with solvent and look for dents/damage in the races. Fit new bearings. – Criggie May 09 '20 at 04:14