Cycling UK Forum

For example lets take a Moulton wheel at 16" (349) and compare it to a 700c.

My initial thoughts are the chances are higher as any thing that impregnates the surface will
get rapidly hammered in much faster than a larger 700c wheel.


Also objects have more opportunity to get thrown off a larger wheel
before they become impregnated into the surface area.

To counter the above is this thought. A smaller tire will rotate faster and apply a greater centifugal force to the anything stuck to the tire. This should make it shed unwanted items better than a larger wheel.

I believe lower tyre pressure will increase the likelihood of
punctures. The higher pressure should make it more difficult for an
object to enter the tyre surface.

The higher the pressure the harder the tyre. Making it difficult to be
impregnated.

Although it has been suggested that lower pressures are less susceptible. I would like to understand why. Aso higher pressure are more likely to puncture due to pinch flats.

After many thousands of miles on 406 and 700C tyres I can't see any difference.

If there is a difference then it is small.

I've punctured once in nearly 12 years with my Birdy although I don't bother recording mileage. That was on the original dodgy tyres. I've used Schwalbe Marathons since they became available in that size. I think byegad has summed it up.

I haven't owned a small wheeled bike since the 1970's, when my dad would have mended any punctures .

I imagine that small tyres wear out quicker, reaching that point in their lives when having less rubber to the tread, they're going to puncture more easily.

Your idea on higher centrifugal force would need to be proven. The object will probably be stuck in quite well (such is the nature of rubber for grippiness) and it's also relatively light - both these effects would readily counter centrifugal force expelling the object.

I'm trying to understand why a high pressure tyre is going to be more puncture resistant and yet this is what I hear and what you're saying here. The actual material of the tyre isn't going to be any harder to penetrate, is it? With a lower pressure tyre, it's more likely the carcass and rubber will yield to an object's shape. At least this is how Marathon Plus's work, though the special rubber employed is amazingly repellent and springy. That's my theory anyway .

They are more prone to punctures because the radius is tighter, therefore (if the pressure is the same), the contact patch is wider, therefore they "sweep" more road than a tyre on a larger wheel of the same carcass width.

Likewise, all other things being equal, a narrow tyre is less likely to hit that thorn or piece of glass than a wide tyre, because it touches less road widthways. Extrapolating to silly extremes, a 10-foot wide tyre will pick up every thorn and piece of glass on the road.

In practice there are complications because narrow tyres tend to be more lightly constructed and run at much higher pressures, both of which may increase some tyres of puncture.

To counter the above is this thought. A smaller tire will rotate faster and apply a greater centifugal force to the anything stuck to the tire. This should make it shed unwanted items better than a larger wheel.

Not my idea but a suggestion by somone else to counter my thoughts.

Which were:

Also objects have more opportunity to get thrown off a larger wheel
before they become impregnated into the surface area.

I posted thm in the wrong order but it's now fixed.

I was thinking more of the comparison between 16" to 700c although 20" are also a good example.

Most sharp objects will either penetrate the tyre on the first rotation of the wheel, or will embed themselves deeply enough not to be troubled by a bit of centrifugal force*, which isn't really very significant when you're talking about the weight of a shard of glass.


*physics pedants will point out that there is no such thing...just centripetal force (caused by the tyre gripping the object object) stopping the object from flying off in a straight line, which is what it really wants to do.

rogerzilla wrote:*physics pedants will point out that there is no such thing...

we don't need to now you've done it for us

I would imagine the pressures and the tyre design are the important factors.

I would say wider bigger tyres are more prone to puncture, lower pressures and more tyre in contact with the road. The circumference isn't really a factor.

gilesjuk wrote:I would imagine the pressures...are the important factors.

OK, but how does pressure affect puncture susceptibility?

If a wheel has a small diameter, it goes round more per unit distance.
Therefore any one part of the tyre must have more opportunity to puncture if a thorn (or something) was to be picked up as it would be run over more times.

Valid argument?

No disrespect intended,but I normally ride me bike and worry about punctures when they happen.Just to add to the confusion, if I rode my fixed 700c wheeled bike backwards and therefore riding in the opposite direction to which I would normally travel, would I be less likely to pucture, having ridden in the opposite direction and not punctured previously

CREPELLO wrote:

gilesjuk wrote:I would imagine the pressures...are the important factors.

OK, but how does pressure affect puncture susceptibility?

I seem to find that running low pressure means more punctures.

Of course the pressure of the tyre doesn't make the tyre material stronger, but a flatter tyre covers more road and you can go over a bump and get a snakebite puncture if the pressures are too low.

Mick F wrote:If a wheel has a small diameter, it goes round more per unit distance.
Therefore any one part of the tyre must have more opportunity to puncture if a thorn (or something) was to be picked up as it would be run over more times.

Valid argument?

Although each bit of the tyre is hitting the road more frequently, there are fewer bits of the tyre doing so and at any given time there is only one bit of the tyre the bottom - in contact with the road. That must mean that the overall rate of wear of a smaller tyre is quicker - less tread so it wears faster - but I cannot see how it increases puncture rate. On the same theme, somebody suggested that once the foreign body had lodged in the tyre, a smaller wheel would come round faster during the hammering it in phase, but that would not increase the number of punctures. The only thing anybody has suggested that I can see making a noticeable difference is the way a larger wheel copes better with a rough surface. Presumably the threshold height of, say, a kerb which would be likely to cause a pich puncture would be appreciably lower with a 26" wheel than something half as large again.

There was an article in the CTC mag about this (or maybe a letter) which concluded I think that smaller wheels are more prone to puncturing. It must be pretty marginal though.