I was riding my bike today and it suddenly exploded. I have attached a picture.

The tube was not over inflated and I haven't been riding on rough surfaces.

What happened? Was the tube or tyre faulty? Do I need to reach out to the bike manufacturer?

enter image description here enter image description here


I went back to inspect the road closer. In the end, I found what caused this issue. It was a shell, stuck in a crack in the road, which was impossible to see because of the road levelling. I'd say, really bad luck.

enter image description here

I will send my wheel to inspection, and hope I won't have to replace the rim as well.

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    The rim appears to have cracked under the slash - that’s not good. – MaplePanda Nov 4 '20 at 16:28
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    Are you okay??? – DKNguyen Nov 4 '20 at 23:14
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    FWIW, these tyres are Continental GP5000, racey, high quality but not exactly the most robust. – Lamar Latrell Nov 5 '20 at 0:00
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    @DKNguyen yes, luckily I wasn't going too fast and I could safely stop afterwards. Thanks for asking. – linkyndy Nov 5 '20 at 8:31
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    @MaplePanda: Not a crack, just a small burr/cut. – Michael Nov 5 '20 at 8:50

TLDR answer: you ran over something

Given the ding/cut in the rim itself that aligns with the cut in the tire, you ran over something metal that was sharp enough to cut your tire and even dig into your rim a bit.

That looks like a deep carbon fiber rim - if so, I'd recommend doing a better job watching what you're riding over because the next bit of debris might be enough to seriously damage your rim - which will be expensive to replace if it is a deep carbon rim.

Nevermind that getting a flat tire in any circumstance can be dangerous if it happens at any decent speed.

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    Thank you for your answer. If this was an accident, then it surely was a very unfortunate one; the road was smooth and there was nothing on the road I could see while riding, or while checking the road after the accident. Do you think I need to do anything about the rim? – linkyndy Nov 4 '20 at 15:24
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    I’d check for trueness (or any other damage) of the wheel and smooth down the burr with sandpaper. – Michael Nov 4 '20 at 15:53
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    Any idea what kind of object could have caused this? I mean, a kitchen knife lying around on the road edge-up seems a bit unlikely, but it's still the best I can come up with. – MaxD Nov 4 '20 at 23:40
  • I think it must've been something like this, though a knife would be pretty visible. I was also thinking that maybe the dent in the rim was caused by it hitting the ground after the tyre exploded; however, the shape of it might not suggest that. – linkyndy Nov 5 '20 at 8:33
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    You'd be surprised how small an item can cause damage like this. A twisted piece of metal half an inch /12mm would have been plenty long enough to cut like this - remember the cut happened when this point on the wheel was on the road, so it was compressed. Even a sharp stone might have been enough. It could also have been a piece of broken glass. – Criggie Nov 5 '20 at 10:38

Definitely a cut - the damage to the rim and the fact that the rubber and carcass fibers are clean cut through confirm that. If the tire burst from over pressure you'd see ragged edges. Also, from what I remember of mechanical engineering classes in college tubular shapes split along their axis when over pressured, not across.

My first thought when looking at the picture was that the tire was slashed with a knife. You may have also run over something that cut the tire some distance before it failed. The tire may have held up for a short while with the perpendicular cut before splitting along the bead which is what caused the catastrophic failure.

  • I believe if it was cut by something to this extent, it should've been cut on the spot; I doubt I could've ridden some distance after something that would cause this slash. Still, I am puzzled by what actually could I possibly have run over. – linkyndy Nov 4 '20 at 16:42
  • @linkyndy see clarifying edit to my answer – Argenti Apparatus Nov 4 '20 at 16:46
  • I see. I heard a pretty strong explosion and the tire immediately deflated, I think that would mean it all happened at once. Does it make sense? – linkyndy Nov 4 '20 at 16:48
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    It's possible that the tyre was cut down to the puncture protection earlier, lost its structural integrity, and burst when you heard it. BTW both blowouts I've had have been parallel to the bead, one overpressure (stuck gauge) the other unexplained, supporting your (Argenti's) recollection – Chris H Nov 4 '20 at 17:07
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    Bottom of a bottle acting as a caltrop. – Carel Nov 4 '20 at 19:11

For readers’ reference, the tire is a Continental, likely a Grand Prix 5000. I recognize the sidewall markings, as I have a pair of these.

The OP specified that these were tubed clinchers, that the tire wasn’t over-inflated, and that it failed without apparent warning. This could be worth reaching out to the tire manufacturer, Continental. You would approach the bike manufacturer for an issue with the frame or fork. However, I suspect this is a cut from something on the road, with explanation forthcoming.

The tire has to have failed first, rather than the tube. If the tube failed first, the tube would deflate immediately without damaging the tire. It looks like the tire might have been cut by a piece of debris. A small cut may cause the tube to pop, as it stretches out of the hole, but the tire shouldn't have taken further damage.

It looks more likely that the tire could have taken a large cut, and that the piece of debris in question could have sliced through the tube simultaneously. In that case, I would assume that Continental would deny responsibility. It’s possible the tire casing was faulty, and that it ruptured while riding. The casing is actually like a piece of (synthetic) fabric, and in that case, I would expect to see torn threads around the failed area. I will say that normally, even riding on rough surfaces should not usually cause failures like this. People can and do ride smooth racing tires on dirt roads. If this wasn’t a manufacturing defect, this was a freak accident.

I’m not an expert on tire failure modes, but again, it could be worth asking Continental. Alternatively, since most people buy bikes through a bike store, the OP could approach the store for advice. Unfortunately, I see some damage to the lip of the rim. I fear this warrants replacement, because a crack in that region could propagate. Remember that the rim is under considerable pressure from the tube inside the tire.

If the OP had specified a tubeless installation, one thing to ask would be if the rim was a hookless design. Continental is a bit of an outlier right now, in that it specifically doesn’t allow installation on hookless rims. Rim manufacturers are only just starting to move towards hookless. On the off chance that this rim is hookless, then any failure would be the OP's fault, unless the bike manufacturer set this up and sold it. That would be a major unforced error. However, the likely failure mode here should be that the tire just blows off the side without tearing. NB: you should still never reuse a tire that’s blown off, as the bead should be assumed compromised.

  • Indeed, the tyre is a Grand Prix 5000. I will reach out to the bike manufacturer and Continental, but as you describe the issue, it seems to have been my fault here; even though, I've never spotted what actually triggered this, after a road inspection. – linkyndy Nov 4 '20 at 15:26
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    A GP5000 has some puncture protection. A big clean cut like that would have taken something very sharp; although the sidewall seems a little torn the tread looks as if it had been cut with a knife. You'd need an unusually sharp-edged piece of debris or road ironwork. I haven't tried a GP5000 but have cut an old Marathon Supreme, and it take some effort. I'd check the other tyre too. – Chris H Nov 4 '20 at 17:04
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    The cut continues into the rim, which pretty much rules out tire failure. – Michael Nov 5 '20 at 8:48
  • @ChrisH a gp5000 has much less sidewall protection than a marathon supreme - they're different classes of tyre completely. bicyclerollingresistance.com/tour-reviews/… vs bicyclerollingresistance.com/road-bike-reviews/… But the "sidewall ratings" are now members-only data. Bother. – Criggie Nov 5 '20 at 10:41
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    @Criggie the supreme has next to no sidewall protection - I've lost 2 that way; I liked them because they roll nicely due to the supple sidewalls. But it does have much more tread protection, and that where the cut is. BRR.com's categories are a bit arbitrary (blame manufacturers; see e.g. Durano which is popular for touring and road), but valid for this comparison. However GPs are still puncture-protected and good quality tyres; they'd still take force and sharpness to get a clean cut like that even if not as tough as Supremes – Chris H Nov 5 '20 at 10:58

enter image description here

I guess it was something like a blade, a metal sheet or similar that sliced through the tube, hitting the wheel at a very shallow angle (kind of like the Titanic, it could stand a head-on impact with an iceberg, not a side scraping close contact).

I wonder if the crack is on the rim, it looks there are fibers there ... is it the tyre or the rim? If it is a carbon rim, consider it waste and dangerous to ride.

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    I've found out what actually caused this accident; I've edited my original post. As for the crack, it is on the rim, however it feels like just a bit of the outer (painted) layer was chipped. Not sure if that's enough to throw away the whole rim. – linkyndy Nov 6 '20 at 10:24

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