Is an innertube blowout due to heat likely in the uk?

[Profpointy]

Laws of physics:

increase temperature by 10% , the pressure must also increase by 10% (let's say constant volume)

Bear in mind this is termperature in Kelvin, so from moderate 10C (=283K) to scortching 40C (313k) is sitll only 10% or so. Do you really pump your tyres to within 10% of bursting point?

I guess you could pump them up really hard in your trip to the North Pole, then fly straight to Africa and get a really fat bloke to sit on the bike over a big bump and you might have problems ,...

 

[GrasB]

Solar gain is also important. I've had tyres & rims too hot to touch with gloves on after climbing up a mountain in 10-15C air temps.

 

[Profpointy]

Ah

Solar gain is also important. I've had tyres & rims too hot to touch with gloves on after climbing up a mountain in 10-15C air temps.

Ah good point. I'd only covered half the physicis, dunces cap on

 

[User482]

Laws of physics:

increase temperature by 10% , the pressure must also increase by 10% (let's say constant volume)

Bear in mind this is termperature in Kelvin, so from moderate 10C (=283K) to scortching 40C (313k) is sitll only 10% or so. Do you really pump your tyres to within 10% of bursting point?

I guess you could pump them up really hard in your trip to the North Pole, then fly straight to Africa and get a really fat bloke to sit on the bike over a big bump and you might have problems ,...

Heat from braking substantially increases temperature, particularly if you have poor technique and are using carbon rims.

 

[snailracer]

I doubt it would be purely heat related unless you pump your tires up to very high pressure to start with.

If I remember O level physics right. Say you start at 100psi and the air in the tyre goes up from 25C to 50C. The pressure is then 108psi - not enough to cause problems.

I reckon tubes fail when they're hot mainly because the material weakens. As you rightly point out, the pressure doesn't increase much.

 

[fossyant]

I've not replied yet but this is my opinion.

Latex tubes go flat over a week. If you've gone to the bike, then pumped them up WITHOUT checking the tube hasn't been pinched, then they will go bang at some point. Don't ask me how I know, but all I will say is I gave a dog walker an almighty fright at 6:30am before the start of last Year's Manchester 100. BOOOM !

 

[Bodhbh]

Last summer I had a couple of slow flats from the inners getting a nick from the rims - despite the rims being well taped up. Both times happened when the bike was parked in the sun - 26 x 2" touring tyres pumped up fairly hard for the volume (60-70psi). I stopped pumping them up by 10psi and hasn't happened again. All conjecture, but my hunch is the temp was the straw that broke the camels back.

 

[Waspie]

Attached is a picture of said tube. The tear is about 3cm long overall.

@fossyant - I had been using the bike the night before so they hadn't got the chance to go really flat. It is quite loud though when they go!

 

[Iain M Norman]

When braking on long descents rims can get very very hot. If there's a defect somewhere then if that tubes gonna go, it's more likely to happen in said hot rim heavy braking situation.

Were they carbon rims? Even more of a problem heat-wise.

Did you use cadence braking?

* For anyone who's not come across the term it's where you pulse between front and rear on a long descent to avoid build up of heat and brake fade

 

[Berties]

I thought the same had happened to me,just entering a strava seg with the queen of the seg trying to keep up 8% going down at about 30mph and bang the front wheel blew out,held it straight but my golden shot was twitching,but it was 1 inch flint gash in yet another gator skin!!!!!
but have noticed in the heat need to let a little air out of my tubes

 

[Shut Up Legs]

You braked hard and sharp, you probably just pinched it rather than it being heat related, the hot rim is only a coincidence. I ran those Long Alpine descents in heat a few weeks back and never had a problem even with my heavy braking

Agreed. I have a hilly commute, and back in March we had an extended heatwave with temperatures in the mid to high 30s. I run both my tyres at 100psi or near enough, but have never had a tube blowout due to heated rims.

By the way, one way to reduce the chance of this happening is to (a) brake intermittently if you're using both brakes together, or (b) alternate between the front and rear brakes. I had to do this when descending Mt Baw Baw late last year, which is pretty steep: http://theclimbingcyclist.com/climbs/baw-baw-national-park/mt-baw-baw/

 

[GrasB]

Pump the tyres up to 110psi when it's 10C in the morning, go for a long climb in the hot sun, or in my case hang the wheel up in a suny spot outside, wait 4 hours & come back to find the tyre pressure at 135psi I managed to burn my finger getting the valve open. Now what do you think will happen if I was to throw my bike down a steep descent from that state?

A 140psi rated tube & tyre shouldn't let go until well over 280psi, however there are lots of things which can reduce that pressure to less than 200psi. As the temps rise then the rubber will soften. Any hard edges in the wheel will exert more pressure on the tube. Any imperfections in the tyre &/or tube will be further stressed by the heat. As the pressure rises there will be more movement transmitted into the rim which may lead to internal chafing of the tube against the tyre &/or rim. These will all lead to a premature failure.

Unless the tyre was ludicrously under pressure then braking hard will never pinch the tube without the interference of a fairly substantial raised edge.

 

[Waspie]

When braking on long descents rims can get very very hot. If there's a defect somewhere then if that tubes gonna go, it's more likely to happen in said hot rim heavy braking situation.

Were they carbon rims? Even more of a problem heat-wise.

Did you use cadence braking?

* For anyone who's not come across the term it's where you pulse between front and rear on a long descent to avoid build up of heat and brake fade

No, alloy rims.

Cadence braking isn't a term I'm familiar with, but it's what I usually do. However, in this case I was just trying to scrub the speed off as quickly as possible to avoid reaching the corner at the same time as the lorries.

 

[Waspie]

Pump the tyres up to 110psi when it's 10C in the morning, go for a long climb in the hot sun, or in my case hang the wheel up in a suny spot outside, wait 4 hours & come back to find the tyre pressure at 135psi I managed to burn my finger getting the valve open. Now what do you think will happen if I was to throw my bike down a steep descent from that state?

A 140psi rated tube & tyre shouldn't let go until well over 280psi, however there are lots of things which can reduce that pressure to less than 200psi. As the temps rise then the rubber will soften. Any hard edges in the wheel will exert more pressure on the tube. Any imperfections in the tyre &/or tube will be further stressed by the heat. As the pressure rises there will be more movement transmitted into the rim which may lead to internal chafing of the tube against the tyre &/or rim. These will all lead to a premature failure.

Unless the tyre was ludicrously under pressure then braking hard will never pinch the tube without the interference of a fairly substantial raised edge.

I had been on a reasonably lengthy climb just before the descent, so that could have exacerbated things.

 

[Ed no-more-lemons]

Going back 15 or 20 years, I had this on the flat and it was a temperate day. I think it was the front tube that went and at the time, in that split second that went bang I did not have a clue what had happened,

I don't think I had pinched the tube or resently refitted it, as I recall my disgust at having to traipse several miles to buy a replacement.

The tyre did not need replacing though it may have been 'quite' worn and the tube was most likely a tad ropey. But no signs of previous damage just a new ruddy great hole in the affected area.

I suppose an in-built defect or something like metal fatigue, may on occasion prove the cause, no idea of coarse how this might relate to latex tubes!