How does a nail puncture a tire? (2003) | Hacker News Reader

How does a nail puncture a tire? (2003)

madsci.org

66 pointsluu41 comments

There is one more mechanism there - when the front tire rides over a nail it can can "make it stand" setting it in a position dangerous for a rear tire. That is a known issue and was brought to me by my father that was doing some work at nails factory. Their solution was to limit the maximum car speed to at most 20 km/h to give nails time to "lie down" before meeting the rear tire.

To make it more than anecdotal evidence one could try to reach statistics about nail punctured tires - if there will be much more rear punctured tires than the front ones, that would support the hypothesis.

Of course my father didn't listen and punctured his tire. The rear one.

Front tires might also kick up the nails, "shooting" nails towards the rear tires.

Not at any sort of velocity needed to puncture them.

Just needs to get it in the right position so it can be forced into the ground (pushing into the tire).

+1 on these, distrubance on nails by front tires that makes them stand up and puncture rear ones feels quite plausible, but naturally we would want to see some statistics on rear tyre punctures by nails are more common.

Luckily I happen to know some people who work with a large towing company with a fair bit of data, so I'll query if it's possible to do a quick query on that.

I have experienced a roofing nail puncture as a cyclist. In Australia roofing nails usually are galvanised with a washer to spread the load held by the head across a corrugated sheet of steel or plastic.

I was riding at around 35 km/hr and believe my rear tyre rolled along the nail from point to head until the tyre hit the washer. The washer then then forced the point of the nail upwards into my tyre, tube and then right through my aluminium rim. There was a very load bang and an near instantaneous loss of tyre pressure. I was lucky it was the rear wheel and not the front so I could keep the bike straight and slow down safely. The wheel wasn't ride-able after that.

In my car the two times I've had puncture were due to roofing screws which also have a built in washer type flange. Again I think the washer/flange acts as a lever helping to flip the point upwards into the tyre. In both cases the car tyre didn't deflate but we could hear the screw hitting the road on every tyre revolution so drove straight to the nearest tyre repair shop to get it fixed.

I just got one of those stuck in my sandal a couple of days ago - presumably from construction next door. Thank goodness they have thick soles. It is basically the worst how they’re weighted and shaped in a way that makes them stand straight up.

My car tyre punctures have typically been the same culprits. I hope the clowns who like to spread tarred tacks on bicycle paths never clue into how effective they are.

This is a surprisingly long conjecture about how tires are punctured by nails and yet it contains very little accurate information about tires and their construction (such as being lined with steel cables).

And spells “tread” as “thread” - or is this some unknown-to-me alternate spelling / definition?

I'm in some hobby groups where the subject of tyres and tread patterns come up often. I swear it's spelled as "thread" there more often than not. I would understand some autocorrect, but it does seem like many people think that's the correct spelling.

I find it amazing when you look at a well-used bike tyre, how much glass and bits of metal shrapnel are embedded in the rubber. When the tyre is new, the rubber is thick enough that small sharp things don't make it through to the tube, but they stay in the rubber, and as it wears down those same bits of shrapnel start to become a problem. Usually with an older tyre, once you get one puncture, there are many more on the way, so it's time to replace the tyre.

This may sound a bit geeky, but I occasionally inspect my tires and pull that stuff out. The two offenders are little shark tooth shaped pieces of hard stone, and tiny bits of steel wire that are supposedly from worn out car tires. But it's true that frequent flats are a sign of a worn out tire.

I find it relaxing. There’s something satisfying about prying out those little shark tooth rocks with a needle.

True, there's something primordial about it, like baboons grooming one another.

Do you frequent r/popping?

The hypothesis that the nail either punctures on the first rotation, or not at all, misses that something is different on subsequent rotations, namely that the nail experiences centripetal acceleration once it is embedded in the tyre. You could imagine that on first contact, only the tip of the nail sticks into a tread block. Then as the wheel rotates, centripetal acceleration causes the nail to be pulled more perpendicular, and on the second rotation it punctures the tyre when it hits the ground. No idea if this is actually a common failure mode, but it seems plausible at least.

All my road bicycle punctures (few per year) are from tube getting pinched against the rim of the wheel. Usually after hitting the pot hole or curb.

pro-tip: never fasten the nut around the valve that holds it to the rim, unless you know with certainty that the road will always be smooth. Any larger than normal bump will rip the tire at joint. Just keep it loosely on, but not tight.

Very good one, and similarly if you get out while it's cold and store your bike in a hot place, don't tidy that screw. I've had it fail once precisely on these conditions

Are you referring to Presta valves? It's ok/recommended to discard the nut on the valve stem?

Yes presta too. I wouldn't discard the nut, since it provides a good support when pumping the tire, but just don't fasten it on tightl - maybe leave a few centimeters.

This thread reminds me of biking in to work with a friend. He managed to pop both his tires on the same wedge shaped rock.

You need more tire pressure then. Either that, or you're using tires with some heavy-duty puncture protection.

Do you not partially inflate the tube prior to tucking the tire bead under the rim? This prevents the pinch in the first place. Source: learned this handy trick in the middle of the northern Nevada desert, ~50 miles from anywhere during a cross country ride, from a perfectly-timed stranger riding the other way.

Interesting older blog site - was this once a popular forum these types of questions? Feels like an old school Reddit

It looks like a mailing list archive, not a blog site.

Interesting way of describing a mailing list archive. It pains me to remember just how much speculating there is in archeology.

I'm having a hard time wording this in a non-condescending manner. I'm honestly interested. Have you been online for a relatively short time? How old are you? Thanks!

Are you sure it’s a mailing list archive and not a forum of some sort?

http://www.madsci.org/FAQs/index.html

It is an old school reddit, most hosted many subreddits, and you could even subscribe to real-time notifications to be sent to you when someone posted a new message. No edit button though.

I ran over a nail on my bike last week and got an instant flat. The nail was about 3cm long and bent at a right angle in the middle. I had just replaced the tire and tube earlier that day.

Solution: put a large magnet in front of your vehicle.

Having sweeped some area with a magnet already to find sharp stuff harmful to grazing animals: rather unpractical because either you need a ridiculously strong magnet (to the point it becomes dangerous to handle it, moreover in areas with ironstone it attracts huge amounts of tiny debris), or it needs to be only a cm above the surface. And not all screws and nails are magnetic.

I know you're joking, but I'll take you seriously anyway. Using a magnet could actually make things worse. There will be some mass that the magnet can lift fast enough to clear a path, but over that mass it will only partly lift objects. There's a good chance it will partly lift objects in this mass range and cause them to stand up whereas previously they would have laid flat and just been driven over.

Yeah, I know, just use a much bigger magnet. Should be interesting at a railway crossing.

I'm imagining an angled flap, to brush things out of the path of the tire.

I also imagine that any idea I could possibly have has been researched and discarded by an expert in the industry.

Related topic - always pay the extra 10% for the tire insurance at Discount Tire; I can't believe they aren't losing money on this.

It’s a form of locking in customers. If I get a flat that I can’t plug myself, I don’t necessarily want to have to go back to any particular tire chain and argue over whether the tire is 55% worn or 45% worn.

We once got the tire policy included at no cost during a promotion. Got a flat that I couldn’t plug. I measured the tread with my treadwear gauge and unsurprisingly, their measurements came up short. When I pulled out my gauge and insisted we go out to check them, low and behold it turns out the tech had “made an honest mistake”.

Why? Do more than 1 in 10 of your tyres get punctured within (checks DuckDuckGo) 3 years of installation?

At one apartment/job combo I would manage to lose a tire every 7-10 months.

Bonus points; I drive an AWD vehicle that requires replacement of all 4 tires if tread is too worn. When this happened I only had to pay prorated on the other 3... definitely paid for itself every time!

(We also have nasty roads in my state, fwiw...)

I assume you're referring to tire insurance or something similar?

do they make segmented tires?

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