I don’t think valve stem caps keep air in. I think they simply stop dirt from getting into the valve stem which could cause it to become non functional or the valve to stick open on the tire to deflate
The ones with the rubber seals keep air in. A lot of new cars have those and a lot of cars with tire pressure sensors require them. Regular covers without the seal don’t keep air in obviously but I still wouldn’t trust the ones 3d printed by a random person because I don’t know what their QC is. The ones that go over original covers are the best either way.
I don’t think valve stem caps keep air in. I think they simply stop dirt from getting into the valve stem which could cause it to become non functional or the valve to stick open on the tire to deflate
The ones with the rubber seals keep air in. A lot of new cars have those and a lot of cars with tire pressure sensors require them. Regular covers without the seal don’t keep air in obviously but I still wouldn’t trust the ones 3d printed by a random person because I don’t know what their QC is. The ones that go over original covers are the best either way.