I can guarantee the original caps aren't airtight either. That's not what they're designed for. The valve is designed to be airtight. The cap only stops dust building up.
A good cap will keep a decent amount of air in and protect the valve from damage. I wouldn't trust a 3d printed cap that I don't know who made and how good their QC is. If I made it myself though I'd be less hesitant. Either way, it's better to 3d print covers that go over the originals.
Bet.
One of the tactics of the extinction rebellion is to open the stem cap, place a lentil in the valve, and screw the cap back on normally. The tire will deflate over the next few hours.
I can guarantee the original caps aren't airtight either. That's not what they're designed for. The valve is designed to be airtight. The cap only stops dust building up.
A good cap will keep a decent amount of air in and protect the valve from damage. I wouldn't trust a 3d printed cap that I don't know who made and how good their QC is. If I made it myself though I'd be less hesitant. Either way, it's better to 3d print covers that go over the originals.
Bet.
One of the tactics of the extinction rebellion is to open the stem cap, place a lentil in the valve, and screw the cap back on normally. The tire will deflate over the next few hours.