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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 08-23-11, 08:11 PM   #1
Guy Burns
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Strange Puncture - how did this happen?

I was riding on the verge of a 4-lane highway, when I heard a regular thump-thump-thump. Got off the bike, the tyres were okay, pushed the bike and again felt the thump-thump-thump. Had a closer look at the back tyre and there was a 6" piece of rod that looked very much like a part of a bicycle spoke (without the curved bit though), sticking through the wall of the tyre. The rod had completely penetrated the tyre and was sticking out 2" on either side. Same direction as the handlebars, just to make things clear.

I didn't have a flat at this stage, but when I pulled it out I did. I should have kept the rod, but I tossed it away in disgust. I don't really know what it was, but let's say it was part of a spoke. It was not one of my spokes. None of mine were broken.

What could have caused this spoke to penetrate my tyre? The reason I am concerned is that if it penetrated my tyre, it could just as easily have penetrated my leg.

I have some theories:
1. Self caused. I ran over the spoke and somehow it was catapulted into my back tyre.

2. A car ran over the spoke and "pinched" it under a wheel, giving it enough horizontal velocity to penetrate my tyre.

3. Someone had set up a booby trap by the side of the road.

4. Some local lout had invented a gun to shoot bicycle spokes and aimed it at my tyre.
I have mentioned this puncture to some cycling friends. None could come up with a believable explanation. One of them was so interested that he rang the Police and asked if they were aware of any mechanism that could fire spokes. They said no. Then we went to look for it, but no luck.

Has anyone else had a puncture like this?
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Old 08-23-11, 09:28 PM   #2
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I'd really like to see a picture of that. Too bad you tossed the "spoke". I put spoke in quotations because neither I, nor you can be 100% sure that it is a spoke from a bicycle. Was it sharpened?

I don't think 1 is very likely. But it is possible. I don't think #2 is possible because I've heard of it happening with 2x4s, but I don't think a spoke-like object has enough surface area for a car's tire to grip it and throw it. 3 is possible, and probably the most likely. 4 is also possible, but I think it would be the first thing I think of when I see it happening... Always thinking of those people who are out to get me......
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Old 08-23-11, 09:42 PM   #3
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Any sort of road debris can get picked up by your tires and cause a puncture. I've had nails, glass, stones, steel strips, and yes, a piece of bailing wire about 6 feet long that punctured the tire and wrapped around the axle before I could stop.

The difference between the tire and your leg, is between 5 and 20" in height above the road surface. I've had stuff (most commonly twigs) get kicked up by the front wheel and hit my leg, but never come close to being injured by anything. I'd limit my worrying to my tires, because the odds of a leg injury from something like this is tiny compared to the other hazards you face riding bikes.

Side note. Flats are one reason I hate those bike lanes painted onto the right side of the road. I call the right road edge the debris zone. Car tires tend to clean the road tossing debris to the right where it stays because the cars don't cross the white line to move it farther over. If you keep your eyes open, and ride slightly more to the left (traffic conditions permitting, of course) you'll be out of the debris zone and get far fewer flats. (unless a car flattens you)
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Old 08-24-11, 01:39 AM   #4
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I'd go for #1. I've seen my brother acquire a 5" nail "straight" through a tire. Not particularly well aligned, but in one sidewall and out the other. Given the location where that happened, the other options are just too far-fetched.

Well, maybe someone was in the habit of dropping the occasional nail in the intention of causing mischief. But given the circumstances, that would have been really a long shot.
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Old 08-24-11, 03:20 PM   #5
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I'd go for #1. I've seen my brother acquire a 5" nail "straight" through a tire. Not particularly well aligned, but in one sidewall and out the other. Given the location where that happened, the other options are just too far-fetched.
I've seen nails go through both the tire and the rim when run over. Not a happy situation with an expensive wheel!
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Old 08-27-11, 08:14 PM   #6
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I would guess that the debris initially entered your tire in only one point, but as the tire rotated it likely contacted your chainstays, etc. Contact forced the debris sideways and thus the metal "spoke" was forced out the other side of your tire.

Three possible sources for the metal thing you describe - road flare support, windshield wiper insert or road sweeper bristle.
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Old 08-27-11, 10:21 PM   #7
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I've seen nails go through both the tire and the rim when run over. Not a happy situation with an expensive wheel!

I've had a nail get punched through the tire and rim hard enough that the tire continued to hold air! The only evidence was the thump-thump-thump as I rode along. When I deflated the tire to fix it, I couldn't remove the tire- the nail was embedded in the rim. (I had to call my wife to rescue me.) Even Vice-Grip pliers weren't enough to remove the nail- I eventually unlaced the rim (with tire still attached) and put on a new rim & tire.
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Old 08-27-11, 10:33 PM   #8
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I would guess that the debris initially entered your tire in only one point, but as the tire rotated it likely contacted your chainstays, etc. Contact forced the debris sideways and thus the metal "spoke" was forced out the other side of your tire.

Three possible sources for the metal thing you describe - road flare support, windshield wiper insert or road sweeper bristle.
+1

Could also be one of those flags used to mark utilities, or lwans that have been treated. The plasric flags come off quixkly, but the wires last and last.
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Old 08-27-11, 11:57 PM   #9
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Just consider yourself lucky that you weren't this guy at the Track Worlds this year. Photos in news story may not be suitable for those with weak stomachs.

http://www.dailymail.co.uk/news/arti...shes-race.html

That was a REALLY freak accident, though, and it happened after he crashed and smacked the boards, not while he was JRA.
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Old 08-28-11, 05:07 AM   #10
Guy Burns
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Thanks for the responses. So it does look like this sort of puncture has happened before. And FBinNY's comment about the debris zone rings true. I can think of three punctures in as many years that happened while riding on the verge. I had a close look today – there certainly is a lot of debris on the verge.

That photo of the splinter through the cyclists leg was how I imagined the "spoke" could have ended up - in my calf!
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