Why do tires slowly lose air? From what it seems, they are sealed and shouldn’t really be letting anything in or out, but they still need to be refilled every now and then.

Question

I understand pressure changes as heat changes, but even in the same season you will still lose a slight amount of pressure.

In: 141

Answer 1

They are mostly sealed. It’s really really hard to create a perfect seal between a tire and a rim. We can come pretty close, but it’s not going to be a perfect seal. Keep in mind there’s literally around a thousand pounds of pressure on each tire all the time, they are in motion a good bit of the time, and they are constantly heating and cooling throughout the day and as the vehicle is used. And remember that the materials that make up the tire and the rim expand and contract at different rates as they are heated and cooled. All of these things make it extremely difficult to create a perfect seal between tire and rim. But considering modern tires can often go from months without having to add air, the engineers do a pretty good job with the materials they have and the conditions those materials endure.