Heat and tyre deflation

[Canardly]

Came to prepping the bike for a ride tomorrow and discovered a slow flat to the front. Now this will mean that the last ride out had three visitations on a single journey which is unusual but not unknown. Can the exceptionally high temps recently be at work here? The bike has been kept inside the house. Done all the usual checks of the carcass etc a marathon supreme with about a 1000 miles on it.

[Kim]

Might soften the tyre a bit, I suppose, but I suspect it's more random luck.

[hellymedic]

I doubt it. If the absolute temperature rises by 10%, the volume and pressure will but it's only 10%.

That would be a rise of 27C ...

Glue might melt...

[The French Tandem]

Extreme heat may also soften the tar on the roads making flints more likely to stick on your tyres.

[Diver300]

My brompton tyre had a puncture while in the car on Monday.  A temperature reading from inside the dashboard of the car had hit 56 °C that day. I suspect that there is a connection.

[Brucey]

Came to prepping the bike for a ride tomorrow and discovered a slow flat to the front. Now this will mean that the last ride out had three visitations on a single journey which is unusual but not unknown. Can the exceptionally high temps recently be at work here? The bike has been kept inside the house. Done all the usual checks of the carcass etc a marathon supreme with about a 1000 miles on it.

did you for sure find the offending object the first two times...?  If not it could be a recurrent blighter of some description.

My personal record is 12 punctures from a single object; it was a tiny piece of swarf in the tyre at an angle, which didn't poke out anywhere until the tyre was ridden on. I couldn't actually see the hole in the tread without using a magnifying glass....

cheers

[Auntie Helen]

I have had two blowout punctures whilst my bike was in the car. Another when it was parked in full sun at a cafe when touring with the Wowbaggers in Germany - it went off like a gunshot, having not moved for 10 minutes.

On Sunday when it was 33 degrees here my landlady's bike got a puncture whilst in the car (they had put it in the car one hour before leaving to drive it somewhere).

I think excess heat does cause punctures.

[Kim]

Things can get surprisingly hot when exposed to the sun inside a car with no air circulation.  I'm sure we've all killed a liquid crystal display by doing that at some point.  I had one of those splendid Fisher Price tape recorders when I was a kid (the original NHS beige version) and the darker NHS brown coloured cassette door actually melted after being left in the car (it still worked, but getting tapes in and out required a knack).

Tyres, of course, tend to be BLACK, which makes them excellent at absorbing radiant heat.  The question is what's the failure mode.  Boyle's Law is mostly a red herring unless it's already over pressure.  I reckon it's going to be down to either expansion of the bead allowing it to slip off the rim (as tends to happen in winter when a badly fitted at the roadside tyre is brought indoors), softening of the rubber allowing the tube to escape through an existing hole, or perhaps misbehaving rim tape.

[Cudzoziemiec]

We're talking about two different things here, aren't we? Canardly was talking about actual punctures, ie objects piercing the carcass and tube. Diver and AH (and I could add my own example, stationary bike in a stair well) are talking bout non-pierced tyre explosions.

I don't see how heat causes proper punctures; unless the tyre tread does soften? And there might be more flints on the road from melting tar (you can hear them rattling round inside your mudguards). Explosion-type deflations, yes. 

[rogerzilla]

I had three visitations from different objects in one ride in the 90s.  That's MTBing in hedge cutting season.  Replaced tube for the first one and then had to get the patch kit out.

[Samuel D]

The question is what's the failure mode.  Boyle's Law is mostly a red herring unless it's already over pressure.  I reckon it's going to be down to either expansion of the bead allowing it to slip off the rim (as tends to happen in winter when a badly fitted at the roadside tyre is brought indoors), softening of the rubber allowing the tube to escape through an existing hole, or perhaps misbehaving rim tape.

Agreed that the pressure increase in itself is not the main cause. However, thermal expansion of the bead is not significant and anyway less than expansion of the rim (with steel beads and aluminium rims). With Kevlar beads, I think the bead actually gets negligibly shorter at higher temperatures.

I think blow-offs caused by braking heat or direct sunlight or the greenhouse effect in a car must be caused by the clincher losing its grip on the rim hook at high temperatures, for reasons unclear to me.

It is surprising that cyclists generally still don’t know why tyres blow off rims, other than that it happens with hot rims and/or tyres. Universities have studied far less significant problems!

[toontra]

Another issue in heat is patching tubes.  I had big problems in Sicily a few years back.  Patches, whether Park Tools instants or conventional glued, simply wouldn't stick in the extreme heat (high 30's) no matter how well prepped the tubes were.  Within a few minutes of riding they just came unstuck.  VERY frustrating.

Spent the best part of a day trying to find a bike shop to buy new 26" tubes.