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I was going over a bump. When the front wheel hit the bump, it suddenly stopped moving, the rear wheel lifted off the ground, and I was thrown face-first onto the road. I sustained injuries to the face, hands, chest and knees, and had to go to emergency (see edit 2 for photograph of injuries).

I'm fine now, but I wanted to understand this so that I can be safe next time.

This happened with two different cycles, so I know it's not a defect specific to a unit or to a model. One was an e-bike, with small wheels (maybe a foot in diameter), poor or no suspension, and was going at its maximum speed of 25kph.

Since I was asked, here's a photo of my riding posture:

enter image description here

The brake:

enter image description here

And the brake lever:

enter image description here (These were taken on another unit of the same model, but they're identical AFAIK.)

The other cycle has the usual-sized wheels, no suspension, and was going at 25kph or slightly slower.

In both cases:

  • I was going more or less straight.
  • The road was dry.
  • I never pressed either brake.
  • The bump was tiny, half a cm at most, and the bike can navigate much bigger bumps at full speed safely.
  • The road was otherwise smooth.
  • It was the front wheel that caught the bump.
  • I was thrown over the handlebars.
  • There was no indication of anything going wrong before I was thrown over the handlebars — no skidding, no scraping sound, no loss of balance, nothing.
  • The vehicle didn't have apparent damage either before or after the incident.
  • I wasn't carrying any loads.
  • I didn't have loose clothing that can get stuck somewhere.
  • I wasn't applying the brakes.

Is it because the bump caused the front brake to apply spontaneously? Is there anything I can do to be safe, because at this point, I'm a little concerned about using bicycles or e-bikes any more.

  • 6
    You really mean 0.5cm? Is it possible you always ride with hands ready on the brake levers, and accidentally squeezed them as a reaction to hitting the bump, possibly without noticing? You are yourself the common factor in the 2 cases apart from the bump, and the chances a tiny bump would somehow lockup anything on the bike itself are small (i.e. so hard to find a mechanical reason which makes any kind of real-life sense). What brakes were on the 2 bikes? Or do you perhaps know the exact models? – stijn Jun 2 at 7:04
  • 2
    Did both events happen in the same place? Please consider stopping there and adding a photo of the cause to your question too. Or provide a link on Google Maps Street view if its useful. – Criggie Jun 3 at 4:31
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    I'm voting to close this question as off-topic because asker says in comments the vehicle involved was a Yulu Miracle pedal-less electric scooter – Argenti Apparatus Jun 3 at 11:30
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    @VaddadiKartick it has no pedals - its not a bicycle. It has more in common with a low powered motorbike. – Andy P Jun 3 at 12:22
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    This question really does not belong here. You're asking for an open-ended list of ideas, which is outside the mission of stack exchange sites. Then the documentation of your actual incident shows it to be the result of an unsafe electric scooter design, not any sort of bicycle, making pretty much all of the bike responses irrelevant. Unless you can provide details of an actual pedal bicycle incident, including things like if the wheel turns freely now, this question really needs to be closed and deleted, or migrated to a place for motor scooter topics. – Chris Stratton Jun 4 at 13:54
9

If you have quick-release or bolt-up front axle that is not properly tightened, then going over a bump could cause it to come out of the fork dropouts. Normally dropouts are equipped with lawyer tabs to prevent this, but they aren't 100% effective or your bike may not even have them. Once it drops out of the dropout, the fork would then no longer be supported and would drop onto the tyre brining it to an abrupt stop, likely catapulting the rider over the bars.

  • 4
    You'd think the wheel being detached from the bike would be fairly obvious, but if it dropped enough for the brake pads to hit the tyre, that could stop the wheel turning without it escaping. With brakes adjusted very close to the tyre this could happen even with lawyer lips. – Chris H Jun 2 at 12:04
  • I do remember my rear wheel getting stuck when I don't put it in the dropouts properly, but I'm not sure this is what's happening. – HAEM Jun 2 at 13:06
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    From experience (long story, QR was loose, probaly by someone who did not like where i parked my bike) You don't wonder if the front wheel fell off. You go over the bump, and is dawns on you there was no 'landing' and the front of the bike is 'sinking', you look down have enough time to think "that's a strange place for the front wheel, oh ...., this is going to hurt". – mattnz Jun 2 at 21:08
  • @mattnz Ah, that didn't happen to me. – Vaddadi Kartick Jun 3 at 3:36
  • I updated the question with photos. – Vaddadi Kartick Jun 3 at 11:44
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This is inexplicable and we're missing some details.

Any modern bike tyre will be 20mm wide as a bare minimum. Your electric scooter appears to have approximately 2" or 50mm tyres from the photos.

As such a 5 mm bump will be no more than a quarter of the tyre - its not even going to snake-bite at normal pressures. At 10% the height of the scooter's tyre it shouldn't even be noticeable.

Here's my guesses and why

  • The rental bike was poorly maintained and there's something significantly wrong with it.
  • Complete and unexpected failure of a bearing would jerk the bike suddenly.
  • The electric brake "suffered an uncommanded activation" - that is it came on without your input (less likely - would have been a big skid not an OTB)
  • Some other rider shoved an obstruction into your wheel unnoticed, or a stick lodged into your wheel unnoticed. This would have broken/dented/bent spokes and probably put a mark on the fork.
  • Something you're carrying caught a spoke unnoticed.
  • Something you're carrying wedged in between a wheel and the frame, or a wheel and the brake.
  • Something was across the road that you didn't see - a trip wire.
  • The hole was much deeper than you realised? Perhaps measure it.

All in all I feel there's some assumed knowledge that we're missing, hence the request for photos. I'm not doubting you, just there's something unstated.

Given there's two different bikes, with similar reactions, I am wondering if the common factor is the rider, your technique, your clothing, your shoes, or even something you're not aware of, like your physical ratios, or your bone structure affecting posture leading to something.

This is a fascinating question - please add more info and we'll see where it goes.

  • 1
    Thanks very much. To answer your questions: I wasn't carrying anything. I didn't feel a jerk at all. It was traveling smoothly and the next thing I know I was flying in the air. No wire across the road. I travel by the same road every day to office. If the electric brake spontaneously activated, that's the rear brake — the front one isn't electric and that's the wheel that suddenly stopped. I had no loose clothing. As far as my posture, I often slouch, but nothing else I'm aware of. – Vaddadi Kartick Jun 3 at 7:22
  • I updated the question with photos – Vaddadi Kartick Jun 3 at 11:42
  • @VaddadiKartick All I can think of is maybe the scooter was faulty. And I'm gobsmacked that you weren't wearing a helmet on a motorbike even a small one like that. – Criggie Jun 3 at 16:30
3

Something getting stuck between the spokes

It's feasible that some foreign object gets in between the spokes and locks the wheel on contact with the fork. It can be a stick laying on the road, but given that OP hasn't noticed it it could be something hanging on the bike, maybe there's some accessory you used on both bikes when the accidents happened?

  • youtube.com/watch?v=xTLSgne_TWQ An accessory would explain it happening twice to the same person. – mattnz Jun 2 at 21:12
  • I wasn't using any accessory, and there was nothing on the road. It fact, it was wide open, trash-free and generally a pleasant stretch. – Vaddadi Kartick Jun 3 at 3:41
  • I updated the question with photos. – Vaddadi Kartick Jun 3 at 11:42
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    @Vaddadi Kartick can you inspect the whole again, I'm thinking there might be another hidden whole, maybe covered in soil or water in the middle of it that's actually much deeper. Try to poke something in the middle of it. * I assume both accidents happened on the same place – Velimir Tchatchevsky Jun 3 at 23:12
  • I will do so when I'm well enough to go out, but the wheel should've traveled over a tiny hole that's much deeper. Both accidents happened in different places, but the question describes all the ways in which they were similar. – Vaddadi Kartick Jun 4 at 1:33
2

If both bikes can / have navigated bigger bumps without issue then I'd suspect that the 'half a centimeter' bump wasn't the cause of you being thrown off the bike, that it just happened to be there on the road where you fell off. If these both happened at the same point in the road I'd be more suspicious about it being the large scale road geometry rather than the small scale road geometry of the bump. Maybe the surface has a longish hump followed by a dip, such that it pushes the front of the bike up (several inches) and then a bike length later drops the front wheel into a dip while pushing the back wheel up... the effect would be to tip you forward as the handle bars dropped and the saddle kicked up under you. If you're way forward on the bike or you ride a short framed bike that might be enough to tip you off. I know from experience that some un-flat road surfaces have kicked me up on the saddle... and have dropped the bars out from under my hands... and I've learned to ride over that sort of terrain with my weight not fully on the saddle letting the bike buck around underneath me and using legs as suspension. With poor road maintenance where I live I'm regularly riding routes with bumps much bigger than half a centimeter on 23mm racing tyres running at 90+ psi.

As to why no-one else notices it? maybe they aren't travelling as fast. Maybe they ride in a different geometry. Try riding that part of the journey much slower, you should (1) not get thrown off and (2) have more time to feel the sequence of movements of the bike under you.

Photos of the road surface may help give a clue.

  • There was no hump followed by a dip, or anything usual prior to the single bump that threw me off. I've updated the question with photos. – Vaddadi Kartick Jun 3 at 11:41
  • I went to the scene of the accident, as you asked, but couldn't identify the exact spot, because the bump that caused the accident was so small – Vaddadi Kartick Jun 10 at 12:10
2

Since there's not much detail provided about the physical surroundings of the crash (i.e. no pictures of the road surface or the bump you hit), we're all really stabbing in the dark here. I'll continue that trend...

Looking at the front brake of the bike, it appears to be cable actuated and the cable pulls back on that brass arm. Suppose there was a small hard object in the road that you didn't notice, e.g. a dusty rock or piece of wood that could easily blend into the road surface and be missed at your acknowledged speed of 25kph. If your front tire passed just to the right of said object, the object could impact that arm from the front causing the front brake to suddenly engage.

I.e. in your second picture:

enter image description here

Such an object would only have to be a few inches tall, one of the risks to such a small wheel with so much of the brake mechanics exposed like that. After flying through the air, being injured, dazed, etc., it would be easy to not notice the object, which may also have been tossed out of the way by the impact.

  • As I mentioned, I will post a picture of the crash site when I'm well enough to go there. I'd have noticed an object a few inches high, all the more so if my tyre ran over it. I do pay attention to the road. – Vaddadi Kartick Jun 5 at 5:01
  • I went to the scene of the accident, as you asked, but couldn't identify the exact spot, because the bump that caused the accident was so small. – Vaddadi Kartick Jun 10 at 12:10

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