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I have driven in my life 200 000 km by car and 20 000 km by bike. In my car, I have never had a single puncture. In my bike, my puncture count probably exceeds 5.

Why do bicycle tires suffer from frequent punctures whereas car tires do not?

  • 11
    If bike tyres were as heavy as car tyres, they wouldn't puncture so often. – Brian Drummond Jun 28 at 20:50
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    It should probably be noted that just a couple decades earlier, car tires were far more likely to puncture - probably a combination of better roads, better tire materials, better puncture protection (e.g. many car tires have steel protection nowadays), maybe even cleaner roads, thicker and wider tires... Back when I was a kid, every driver had plenty of experience changing a punctured tire. Nowadays, many cars don't even have a lever to lift the car up (though part of that is probably that people will call for assistance anyway, rather than trying to fix their car). – Luaan Jun 30 at 7:43
  • Not directly an answer to your question, but there is quite a range of quality of bike tires. So far I have had good experiences with tires from schwalbe that are designed to be more resistant to punctures - so if you have frequent issues I recommend looking into that! – flawr Jun 30 at 9:15
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    I had punctures about once every month until I switched to the Schwalbe puncture protected tires. (No affiliation, just happy.) – AndreKR Jun 30 at 10:57
  • Wow, 5 punctures in 20,000 km is pretty good. I get about 3 punctures every 2,000 km. – copper.hat Jul 1 at 4:25
51

The main reason is that bicycle tyres are much, much thinner than car tyres. A little tetrahedron of broken glass or a drawing pin that would puncture both tyre and tube on a bicycle won't trouble a car's tyre in the slightest.

A secondary reason is that bicycle tyres with tubes have additional ways to suffer punctures: an under-inflated tyre is susceptible to pinch flats.

It's pretty much as simple as that.

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  • 4
    And you forgot to mention spoke pokes, due to a poorly built rim or weak rim tape. And then there's punctures due to poor tool use when installing the tire. – Daniel R Hicks Jun 28 at 14:39
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    For reference, I took a caliper to a piece of my retired Schwalbe Marathon summer tyre. The groove near the edge of the sidewall is about 2mm deep. The recommendation for cars is to start thinking about replacing your tyres when the main groove is 4mm deep. – HAEM Jun 28 at 14:55
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    @HAEM: Car tyres need grooves because they have to evacuate water through these. Else the phenomenon known as aquaplaning happens. On formula cars, slick tyres can be used on dry surface only. Bicycle tyres for road use don't need any grooves at all. The contact patch on the road is very small and the pressure on that surface is great enough to push away any water from under the tyre. – Carel Jun 29 at 7:46
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    @Carel The point I was trying to illustrate is how much thicker a car's tyre is compared to a bicycle's. – HAEM Jun 29 at 8:46
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    @Carel "cycling tyres would be considered worn-out right from the beginning" is the point I'm trying to make. – HAEM Jun 29 at 11:23
38

An unaddressed reason is speed-induced wind and the shape of modern roads.

Motor vehicles travel in a lane, and a roadway is generally two or more lanes in opposite directions.

As such, these two lanes meet at the centerline, which tracks the highest point on the sealed road surface. For drainage, the road is not flat - all roads are intended to have some minor slope to assist rainwater to flow off. Also, some corners are cambered, so that the shorter inside of the corner is lower than the longer outer edge.

Bringing it back to the question - we cyclists do not generally ride the centerline. I ride on the outside of the road, which is where road detritus gets washed by rainwater, and debris also gets pushed here by the passage of cars. You can see a similar effect on a flat road just before a traffic island - here's an extreme example, which is mostly gravel and organic leaf matter....

Corner of Hawkins and Marshlands Roads, Christchurch, New Zealand.  From google streetview.

...but I'd expect to find metal wire shards in there and possibly fragments of glass and plastic. Nails, screws, and staples are normal road rubbish too. Basically anything that can be "swept" by the passage of vehicles travelling at 50 or 80 or 100 km/h which creates a respectable breeze to sweep the lane clear and push the jank downhill to the sides.

The side (or shoulder) of the road is where we end up riding. All of these items lie on the road surface, and get concentrated on the sides, and this contributes to punctures along with the other points raised in other answers.

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  • 8
    It's my experience that the objects that puncture bicycle tyres are generally too small to puncture car tyres, while the things that puncture car tyres tend to be so large that bicycle tyres just ride over them. So although I am sure that the effect described in this answer is real, perhaps this makes a difference to it. – Daniele Procida Jun 28 at 20:56
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    This is significantly worse too in areas with hedges. Any hedges or trees along the sides of the road will need trimming, and the trimmed branches will fall on the sidewalk and cycle lane. These are often not cleared up properly. In the UK, hedges of hawthorn, blackthorn and buckthorn are historically used around the sides of fields and properties, and the debris after cutting can be catastrophic for cyclists. – Graham Jun 29 at 7:43
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    @DanieleProcida also, things which will puncture car tires are often large enough to be seen and avoided by cyclists, while they will likely never be noticed by drivers. – FreeMan Jun 29 at 15:53
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    On my old commute to work, a section of "cycle path" (shared with pedestrians) ran past a lorry freight terminal. Whenever we had heavy rain, all the crap would get washed onto the path, and I got at least one puncture a year from that section, util I switched to Schwalbe Marathon Plus. – SiHa Jul 1 at 9:46
11

Essentially all modern car tires have steel puncture-protection belts under the tread surface

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  • 5
    To expand this, a 1.5 ton car with 100 horsepower is ~75,000 watts or 50 watts per kilo. A 100 kg cycle+rider doing 250 watts is 2.5 watts per kilo, so approximately 1/20th that of the car. The motor vehicle has much more power to burn (ie waste) on overcoming rolling resistance from hefty tyres. – Criggie Jun 28 at 21:02
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    a 1.5 ton car doesn't use all the 100 horsepower when coasting. it may use 10-30 horsepower to maintain a 100 km/h speed. @Criggie – Mark Segal Jun 29 at 11:47
  • @MarkSegal Which is still insanely overpowered, imho... – cmaster - reinstate monica Jun 29 at 11:57
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    @MarkSegal We're diverging from the purpose of comments. Feel free to use Bicycles Chat – Criggie Jun 29 at 12:06
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    Steel belts in car tires are not for puncture protection. You simply need reinforcement in a tire which must withstand a couple of tons, and steel happens to be suitable and cheap. Incidentally, it also protects against punctures somewhat. – Dmitry Grigoryev Jun 30 at 8:35
3

As someone who's had three car tire punctures in 200'000 km, and one bike puncture in maybe 20'000 km, I'd say an individual result is simply not statistically significant.

With a car, if you do mostly highway and city driving, punctures are rare. If you go on mountain or country roads, of frequently visit construction sites, railroad depots, junkyards and the like, you'd better have a spare tire ready. The same is true for bicycles: going all-terrain is not the same as riding on dedicated bike lanes.

Other than that, causes of car and bike punctures actually have not that much of overlap. Small glass shards which damage a bike tire are not a threat to cars, and sharp rocks / metal scraps which are dangerous for a car tire can be easily avoided on a bike.

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  • 2
    As a statistician who rides bikes and drives cars, I'd say the statistical significance of that data set is largely irrelevant: it's pretty much unquestionable that a standard bike gets more flats/mile than a standard car :) – Cliff AB Jun 30 at 18:25
  • @CliffAB There's a big difference between cars having less punctures than bikes and "never having a single puncture". I'm not saying that cars have more punctures than bikes, I'm saying that cars have punctures too, and much more frequently than the OP might imagine. – Dmitry Grigoryev Jul 1 at 12:22
2

There are puncture-resistant versions of popular road bike tires. I've got some on my bike from a well-known brand as I bought it and I haven't had a single puncture yet. For the same distance I would have expected 3 or 4 punctures on the tires I used previously.

However, this comes at a cost - higher rolling resistance. Using the site linked below, I see a 9.3-watt power loss versus the race tires of the same brand at 8.3 bar pressure. At lower pressures, the power loss is higher.

I'll probably get different tires when these wear out.

Conclusion: it's possible to make bike tires more puncture resistant, but at a cost. It's much easier to change the tubes on a bicycle than to change the tires on a car, so the trade-off for bicycles is different: people prefer to go faster with the occasional additional puncture.

Site that has a Rolling Resistance Test Result comparison option

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  • On the other hand, there's a cost for a thin tire as well: Let's assume that you fix a puncture every 100km and do 20km/h at about 250W. So one puncture every 5h in the saddle. A 10W power increase translates to an extra energy of 5*3.6kJ = 18kJ energy burned, which is equivalent to 18kJ/250W = 72s saddle time. So, if you can fix a puncture in less than a minute, you are better off riding the thin tire, otherwise, you are better off with a puncture resistant tire. – cmaster - reinstate monica Jul 1 at 13:11
  • @cmaster-reinstatemonica Every 100 km is way too much. Not even professionals get that. Their rides are over 200 km and most oftem do not get a single one in a race. Even fast tyres can get you many hundreds of km without a flat, depending on your riding style. At 250 W you woul be much faster than 20 km/h as well. Unless you are extremely heavy. – Vladimir F Jul 1 at 22:06
  • @VladimirF Depends on the roads you ride. The more gravel and the less smooth tarmac, the more punctures you get. The one-puncture-per-100km figure is from my experience. – cmaster - reinstate monica Jul 2 at 7:24
-6

The reason for bike tires suffering from frequent punctures is simple. In order to have light weight and low rolling resistance, bicycle tires need to be about 30mm in diameter. Car tires can easily have over 8 millimeters of tread, and that's just the tread not the structural parts below it. A tiny shard of glass or a small sharp rock cannot penetrate such a tread and structural parts.

In contrast, if a bicycle tire around ~30mm in diameter had 8mm rubber, the air pocket diameter would be only 14mm. Such a tire would be heavy, have lots of rolling resistance and would not differ much from solid rubber tire.

Some bicycle tires are advertised to be "puncture protected". Foolish riders with the money believe this is a good thing, and has led to disappearance of reasonable non-puncture-protected tires from the market. Fortunately, in the high performance tires segment, the puncture protection is just a thin belt of Kevlar, that protects from punctures no more than a bulletproof vest protects from a sharp knife. The thin Kevlar belt does not add much rolling resistance, fortunately.

The reason for preferring no puncture protection is simple. For example, tests show that the Grand Prix 5000 tire has about half of the rolling resistance (10 watts per tire) of Gatorskin (20 watts per tire). I have used the Gatorskin tires and found them to be lacking in puncture protection despite marketing claims to the contrary. Just by adding minimal, non-sufficient puncture protection adds 10 watts per tire or 20 watts total more resistance. This is 10-20% of the rider's energy expenditure.

Bicycles are mostly limited by air resistance that has a third power law. Thus, 10-20% of rider's energy expenditure lost means 3.2%-6.3% speed lost.

If a bicyclist is using 150 watts average to have 20 km/h average speed, the speed reduced by 4.3% is 19.1 km/h. Thus, the rider lost 0.9 km/h because of non-sufficient puncture protection that won't do much. If the non-sufficient puncture protection (in the style of Gatorskin tires) saves one puncture per 5000 km, about 11.8 hours is lost per puncture that takes 5-10 minutes to repair.

Thus, by selecting tires with less puncture protection, the energy efficiency savings are about hundredfold greater than the time to repair punctures. As puncture takes 5-10 minutes to repair, in a typical distance it won't affect much your arrival time to your destination.

Of course, someone could protest that repairing punctures takes skill. This skill is useful to learn, because no bicycle tire is protected from punctures as well as a car tire is, unless the bicycle tire has more rubber than air, and therefore is more similar to a solid rubber tire than a pneumatic tire.

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  • 3
    @Klaster_1 Tubeless tires mainly prevent snakebite pinch flats. A snakebite pinch flat is often a three-fold user error. Firstly, the user selected a stupid 23mm wide tire whereas a 28mm wide tire would be better. Secondly, the user forgot to inflate the tire often as bicycle tires leak air naturally very quickly -- far quicker than car tires do. Thirdly, the user rode to a hard bump on the road or a kerbstone at too high speed. With often-inflated 28mm tires, as heavy and large inner tube that fits to those tires, and careful riding technique, I have not had any snakebites recently. – juhist Jun 28 at 12:29
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    Your answer could be improved by cutting out the rant starting at the third paragraph. – HAEM Jun 28 at 13:00
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    ...When I was living in Cologne, the Schwalbe protected tyres cut my puncture rate about in half (i.e., ca. every 4 months rather than every 2). That definitely saved me much more time than the bit of rolling resistance cost, and certainly the constant, predictable cost of longer travel time is less of a problem than the time of fixing a tyre when you just happen to be in a hurry. (Not to speak of the time wasted when the puncture happens just when you don't have a pump and spare tube at hand...) – leftaroundabout Jun 29 at 0:55
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    My understanding is that "section height" is the standard term for what you are referring to as "diameter". The diameter of a tire is the distance across the entire tire, not the distance from the outside to the inside. tirerack.com/tires/tiretech/techpage.jsp?techid=7 – Acccumulation Jun 29 at 6:17
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    Maybe my life experience is different from yours, but having never seen a bullet proof vest I have no clue if it protects against knifes or not. – gerrit Jun 29 at 9:05

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