True or false?

When a gas leaks through an orifice, like a hole, it is called effusion. Cold air is denser than warm air, and the molecules move slower. The lighter molecules would leak out somewhat faster than the denser ones.

This would seem to contradict your premise....BUT when is cold and the pressure inside the tire decreases, bead seal also is poorer and the leak may get worse. I think this poorer sealing property is the key to what you are describing.

The bead seal is worse in the cold for other reasons as well as the lower pressure. When it is REALLY cold, the rubber loses is flexibility. That reduces the seal.

Remember the old nylon cord tires that would take a flat spot when parked in the cold, and take a mile or two to get round again, with a lot of clunk, clunking till then?

Air leaks - through the valves - through the bead - through the rubber by diffusion.

During cold weather, there will be more leakage through the bead, but less leakage by diffusion.

--scott

True for rim seal leaks at least. The cold seems to affect the bond between the rubber and aluminum for one type, rims.

Every first cold snap we have multiple flat tires on the aluminum rims. This year we had 7 flats all at once.

I pumped them all up 5 psi 'over' spec for the vehicle sticker and they have held this time.

If they didn't hold like last year, for the last several years we just take them back for the flat tire warranty they have on them. They get a rim clean and seal and hold for another year usually.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

I just checked the tires on the Beretta (aluminum wheels) and the Subaru (steel wheels) for the first time in too long yesterday... (including a lot of -30)

Subaru - no change. Beretta - two are good, one was a couple psi down, and the one that always goes half flat was half flat.

It seems to really depend on the wheel and tire - if you have an ok seal, it might not leak in the summer, but might bleed a lot of pressure in the cold.

Ray

False. cuhulin