Or: use a tire gauge.

If you ride high-pressure tires in cold weather, make sure to drop a few PSI in them before you bring them back inside. I blew a tire today - not a tube the actual tire - and it was not a pleasant sound. I mean we're talking bad "bikes may never be allowed in the building ever again" bad

I stole the pressure*Volume = mu(number of moles of gas)*R(Universal gas constant) *Temperature(in Kelvin) from another similar thread, but long story short, bringing a bike in from a 1.5hr commute in 34* temps to a heated building can up the tubes inflation something like 15psi. Again, this is a PSA, particularly useful if you like having a bike anywhere near your workplace. Then again most y'all ride at 70psi and it doesn't matter!

It's official, you're a terrorist.

Maybe it's time to get some sewups!

170 psi rating should give you some breathing room

The Doc checked my PSA back in September and all was good for another year.

I've never had this problem. In the winter I'll pump the tires to 110-120 psi, go for a ride in sub 20F, come home and park the bike in my heated basement.

But consider this thought experiment: Let's say my tires were 60F at full inflation, and 85% at 20F while riding. Wouldn't they return to something close to 100% after the ride when parked again in a 60F basement? Certainly they would not rebound to 115%.

Do you start out with your tires at 34F, inflate them to your desired PSI, ride the bike in 34F temps, and park in 70F? This would explain the increase in PSI and the explosive nature of your tires. Solution: Park your bike next to your bed at night.

Nitrogen and oxygen, the two gases that make up 99% of air, are ideal gases, and therefore they SHOULD follow the ideal gas law, PV=nRT, wherein T is the temperature expressed in kelvin.

According to the ideal gas law, a drop in temperature of 50 degrees should only cause a decrease in pressure of 10%. Conversely, an increase in temperature should only cause in an increase in pressure of 10%. So, if you pumped up your tires to 80psi at 0F, then brought your bike into your garage and allowed it to warm up to 50 degrees, the pressure should only increase to 88psi.

I suspect, however, that water vapor (which does not conform to the ideal gas law) in the air used to fill tires causes a more radical change in pressure as temps vary, especially when the fluctuation in temps crosses the free/thaw threshold. So, the best way to pump up tires is to use air with as low moisture content as possible. This will minimize temperature-related pressure changes.

Read = the sound of a gunshot.

Ask the landlord if he'd prefer to hear domestic violence and a real gunshot from his replacement tenants as opposed to the quite infrequent sound of a tire blowing off from his otherwise complacent, respectable, current occupant.

-Kurt

You pump up your tire outside?

3 words:

Hook
Bead
Rims

Police: "Ma'am didn't you hear any gunshots?"
Neighbor: "Well I heard a noise, but I thought it was just that guy's bike tires again."

Seriously, the thumb rule for car tires is about a pound for every ten degrees. If you pump them up inside and then go outside, then they will have lower pressure in the cold and come back up when you come back inside. If you pump them up outside in the cold, then you would see the most effect from the thermal expansion. Unless you are testing the limits of the max sidewall numbers, there shouldn't be any issues. A lot of people go well past the max inflation numbers when mounting tires to get the bead to seat correctly.

For an ideal gas, the ratio of the pressures is equal to the ratio of the temperatures (assuming the no volume change or adding/subtracting gas). So

P1 / P2 = T1 / T2

The temperatures HAVE TO BE IN KELVIN. It just doesn't work without the temps in kelvin. 32 degrees F = 0 degrees C = 273 K. 100 degrees F = 38 degrees C = 311 K. This would be one hell of a temperature swing, but would increase the pressure by just under 14%. So that 100 psi tire would go up to 110 psi. Honestly I don't see how the temperature-induced pressure change alone can cause a blow-out when sitting on the bike doesn't. Your butt in the seat has to add more than 14% to the pressure in the tires, even when the weight is spread out over the whole volume of the tire.

Either there is water in the tire and the vapor pressure of the water is changing things (also unlikely; change in vapor pressure is only 6.5 kPa (1 psi) over temp range above) or the bike warming up makes the rubber more pliant and/or the rims expand a touch and a not-quite-properly-installed tire can slip and cause a blow out.

Thanks for bringing us the sanity of science, Stausty. This urban myth gets told so often it ought to be on Myth Busters(maybe it already has).

OP probably had something else wrong with his tire and tube.

I would think the friction of the tire rolling as you ride it should help maintain pressure slightly as well.

Agree with the first part (although I believe everyone in the thread so far has been using absolute temperatures), but not with the last sentence. The only way having your butt on the seat will raise the pressure is by reducing the tire volume. But the volume is unchanged except in the immediate vicinity of the contact patch which only comprises a few percent of the tire circumference. And even in that few percent the volume change is pretty minor. The volume change (and therefore also the pressure change) from sitting down on the bike will be well under one percent - i.e. insignificant.

But the temperature-related changes in pressure, while larger, are still well within the safety margin of tires when inflated to their nominal maximum even in arctic temperatures and then brought inside a normally heated house.

Brand new tire. Brand new tube. Rim strip OK.

And it was a hook-beaded rim.

I was running the PSI very high after having an awful streak of pinch flats. I understand the doubters in this and other similar threads, but I have no other explanation of why it would happen other than a post-ride expansion.

Tires were inflated indoors.

Good that we're discussing this, if nothing else.

I figure that I should put in a little extra air if I'm pumping up the tires indoors, but this thread has been enlightening as to how much.

- Scott

Hmmmmm. I would guess something else caused the explosive outgassing since the tires were inflated at approximately the same temperature as your office is maintained.

Can't think of any reason the rim strip would be a factor - maybe for a pinhole leak but not a blowout unless it was crooked and interfered with the bead-rim interface.

I've seen a dozen or so tire explosions while the bikes were parked - usually a sidewall failure but sometimes a bead blowoff. It's certainly more likely to happen with higher pressures and warmer temperatures but sometimes it happens for no discernable reason at all. Could be you got the new tube pinched in the new tire and it held on just long enough to make it a mystery.

Another thought, Oregon Southpaw: what kind of tires are you using? Seems like the wild temperature swings between indoors and outdoors in winter would favor big, low-pressure tires. Using the ideal gas law, I should only have to put an extra 6psi or so in my MTB tires to go from 70F indoors to -30F outdoors.

- Scott

Yeah, the only tire blown off the rim situations I've had were clearly from tube pinched under the bead. Sometimes they'll hold for quite some time before blowing off. I've been lucky, the couple of times I've done it the tire survived.

Oh and one time using a gas station compressor on a steel rimmed Motobecane. The tire blew off shortly after putting a little too much pressure in there.

OT.... My brother once worked at a service station while in high school. The had on LOL (little old Lady.... the original LOL) who would come in in the fall and have the tires deflated and filled with "winter" air and come back in the spring and repeat to get "summer" air. She was sharp...she watched them removed the valve cores and made sure the old air was out and the tire truly flat.

Then: defective tire and/or faulty installation.

I think you're all missing the relevant information here:

"I mean we're talking bad "bikes may never be allowed in the building ever again" bad "

Oregon - as a generous person, I will gladly "hold" your bikes for you until such time as you can store them responsibly inside

Please don't read the fine print on the contract I'm sending granting bicycle power of attorney!

Did we determine yet whether these are wire bead or Kevlar bead?

-Kurt

I went off to do something else and realized this as soon as I rethought it. The pressure only changes if the volume changes and the tires don't squish much at 100 psi, so the pressure change is truly negligible.