Bicycle Mechanics - How did I crash? *Pics*

I recently crashed going downhill. This hill has residential speed humps, and usually I fly over them with no problems. I was standing on the cranks as I went over the last of them, but as my rear wheel touched back down on the normal pavement it locked up. And I, standing and probably with my hands not gripping the bar, took a bad slide after the tire skidded the bike away from me.

http://oregonstate.edu/~chambchr/roadrash.jpg
http://oregonstate.edu/~chambchr/helmetcrack.jpg

After I stopped sliding I remember thinking that God himself must have come down and squeezed my brake, because that was the most random, non-sensical event ever. I tried to understand what went wrong as I picked my bike up and limped home, but instead of finding the brakes locked or the wheel out of the stays, it was fine. It rolled fine and thankfully, I guess, showed no signs of anything wrong.

So what the hell happened? I went over a hump in the road, and as the rear wheel completed the hump it locked up, causing me to skid out of control at 25 MPH or something.

My ONLY guess is that the rear brakes caused it, because earlier in the day I had increased the tension so I wasn't pulling the brake lever on my bars against the tape on hard brakes. But how does increased tension correlate with the brakes suddenly grabbing? I know they sit closer to the rims while under more tension, but honestly, I had a completely normal and symptomless ride. I had even gone over two humps on the same hill without any problems. Then on the last one, BAM.

Any clue what happened?

maybe the rim flexed under your weight and rubbed against the brake pad?

anyway.. that looks painful. hope you heal quick.

Or you came down at an angle (or on a stone, etc.) and the wheel was not actually stopped, but you simply slid given the angle.

Well, they are called speed bumps for a reason.

Is it possible you squeezed the brake lever without intending to? That could be like a very plausible explanation.

If it was a suspension bike, I'd guess that the full extension/rebound at speed might have tugged on the cable.

I recently crashed going downhill. This hill has residential speed humps, and usually I fly over them with no problems. I was standing on the cranks as I went over the last of them, but as my rear wheel touched back down on the normal pavement it locked up. And I, standing and probably with my hands not gripping the bar, took a bad slide after the tire skidded the bike away from me.

http://oregonstate.edu/~chambchr/roadrash.jpg
http://oregonstate.edu/~chambchr/helmetcrack.jpg

After I stopped sliding I remember thinking that God himself must have come down and squeezed my brake, because that was the most random, non-sensical event ever. I tried to understand what went wrong as I picked my bike up and limped home, but instead of finding the brakes locked or the wheel out of the stays, it was fine. It rolled fine and thankfully, I guess, showed no signs of anything wrong.

So what the hell happened? I went over a hump in the road, and as the rear wheel completed the hump it locked up, causing me to skid out of control at 25 MPH or something.

My ONLY guess is that the rear brakes caused it, because earlier in the day I had increased the tension so I wasn't pulling the brake lever on my bars against the tape on hard brakes. But how does increased tension correlate with the brakes suddenly grabbing? I know they sit closer to the rims while under more tension, but honestly, I had a completely normal and symptomless ride. I had even gone over two humps on the same hill without any problems. Then on the last one, BAM.

Any clue what happened?

I had the rear wheel slip in the dropout and then bind against the frame; which caused the bicycle to stop quickly but I was climbing so I didn't fall.

Perhaps the chain bounced off and wedged between the frame and cassette?

Could be a stone I guess, although that'd be quite a coincidence that I hit a stone which caused me to skid a couple feet RIGHT as my rear tire rolled off the hump.

I know I didn't squeeze the brakes myself, since I didn't have my hands on the handlebar.

I was riding a Poprad, so no suspension.

I guess it could have been the chain, although it was back in gear and ready to serve as a rolling crutch after I got back on my feet, so probably not.

My first visualization of what was going wrong as soon as I entered the skid was that wheel somehow got jammed up into my seat stays. That's how it felt, coming off the bump and then suddenly skidding.


maybe the rim flexed under your weight and rubbed against the brake pad?
Can anyone speak to this? This seems like the most fitting explaination, but knowing little of frames, rims, and flex, I'm not sure if it's even realistic.

Finally, does anyone know if this goo my skinless spots are secreting will stain my shirts? I'm giving the affected areas a breather before bandaging them back up.

I recently crashed going downhill. This hill has residential speed humps, and usually I fly over them with no problems. I was standing on the cranks as I went over the last of them, but as my rear wheel touched back down on the normal pavement it locked up. And I, standing and probably with my hands not gripping the bar, took a bad slide after the tire skidded the bike away from me.

http://oregonstate.edu/~chambchr/roadrash.jpg
http://oregonstate.edu/~chambchr/helmetcrack.jpg

After I stopped sliding I remember thinking that God himself must have come down and squeezed my brake, because that was the most random, non-sensical event ever. I tried to understand what went wrong as I picked my bike up and limped home, but instead of finding the brakes locked or the wheel out of the stays, it was fine. It rolled fine and thankfully, I guess, showed no signs of anything wrong.

So what the hell happened? I went over a hump in the road, and as the rear wheel completed the hump it locked up, causing me to skid out of control at 25 MPH or something.

My ONLY guess is that the rear brakes caused it, because earlier in the day I had increased the tension so I wasn't pulling the brake lever on my bars against the tape on hard brakes. But how does increased tension correlate with the brakes suddenly grabbing? I know they sit closer to the rims while under more tension, but honestly, I had a completely normal and symptomless ride. I had even gone over two humps on the same hill without any problems. Then on the last one, BAM.

Any clue what happened?


DOWNHILL....SPEED HUMPS...NOT GRIPPING THE BAR????!! You were asking for God to show you how not to ride. That is how it happened.
:rolleyes:

Can anyone speak to this? This seems like the most fitting explaination, but knowing little of frames, rims, and flex, I'm not sure if it's even realistic.



it can happen if there is pressure perpindicular to the lateral plane.
it has happened to me but it was only one part of the equation.. also the rear axle was a little loose

Perhaps the brake cable duct slipped out of the guide and snagged on the outer rim of the guide; this might have happened as you hit the road coming down and the frame flexed, unhooking the cable duct from the guide. Then as the frame righted, the duct was hooked on the guide, clamping the brake. It could have easily slipped back into the guide on the crash, revealing nothing wrong.

The only story I have which comes near to this involves a small terrycloth I'd tucked into my belt. I stood up to climb a hill, and hadn't noticed that the cloth was dangling down over the rear wheel. I sat down and started to pick up speed on the downhill part - got up to about 20 mph… and suddenly the rear-wheel locked solid. My first thought was that the tyre had lost all its air - that's just what it felt like. Luckily I was travelling in a straight line, and was able to slither to a halt without falling off. I looked down, and the tyre was still intact and full of air - but there, jammed in between the rear brake and the tyre was the small towel. The skid had worn an eighth of an inch of rubber of the tyre, making a flat-spot about two inches long. I didn't notice the flat-spot at low speeds - it might have been noticable at higher speeds, but what worried me, was that there was now this weak spot on the casing - so I replaced the tyre. The lesson here is to be careful about carrying things which can work loose and fall into the wheels…

- Wil

Finally, does anyone know if this goo my skinless spots are secreting will stain my shirts? I'm giving the affected areas a breather before bandaging them back up.

Cover your rash with Tegaderm. Do it before they start to dry up, and you'll heal much faster and scar much less than if you let yourself get scabby!

I recently crashed going downhill. This hill has residential speed humps, and usually I fly over them with no problems. I was standing on the cranks as I went over the last of them, but as my rear wheel touched back down on the normal pavement it locked up. And I, standing and probably with my hands not gripping the bar, took a bad slide after the tire skidded the bike away from me.

http://oregonstate.edu/~chambchr/roadrash.jpg
http://oregonstate.edu/~chambchr/helmetcrack.jpg

After I stopped sliding I remember thinking that God himself must have come down and squeezed my brake, because that was the most random, non-sensical event ever. I tried to understand what went wrong as I picked my bike up and limped home, but instead of finding the brakes locked or the wheel out of the stays, it was fine. It rolled fine and thankfully, I guess, showed no signs of anything wrong.

So what the hell happened? I went over a hump in the road, and as the rear wheel completed the hump it locked up, causing me to skid out of control at 25 MPH or something.

My ONLY guess is that the rear brakes caused it, because earlier in the day I had increased the tension so I wasn't pulling the brake lever on my bars against the tape on hard brakes. But how does increased tension correlate with the brakes suddenly grabbing? I know they sit closer to the rims while under more tension, but honestly, I had a completely normal and symptomless ride. I had even gone over two humps on the same hill without any problems. Then on the last one, BAM.

Any clue what happened?


It's simple...God had it in for you. ;)

Where exactly were your hands when this happened? On the bars, loosely on the bars, in a victory V?

As I coast down the hill I usually sit-tup straight with almost all of my weight on the sit bones and my hands on the knees. Then, as I approach the speed humps (and they are humps, not bumps) I stand up on the pedals and lean forward with my hands ready to grab the bars if need-be. The goal is to go over the bump fast with only my thieghs and feet touching the bike. It's fun, and since my legs act like shock absorbers, I glide over nicely. Unless random **** happens causing my rear wheel to lock.

my guess is that your rear wheel was airborn for a short time and when you landed, you landed a bit out of line which caused instability and your subsequent crash.

I reckon something got stuck between the seat tube and the wheel, locking it up with massive force, then popping through the gap, which is why you couldn't see any reason as to why it happened