New Tubeless Tires leaking from Molding Sprues. Manufacturing defect? I recently got myself a new Giant Roam 0 with tubeless ready rims and Crosscut AT2 tubeless tires. Everything was assembled at the local bike shop. After having it a few days, I noticed that the tire pressure in the rear tire was going down much faster than the front tire (down from 60 to 30 psi after 3 days), so I tested the tire with soapy water. On the front tire I found no leaks, and the back tire was leak-free around the valve and bead. However, I noticed some slow bubbling around the molding sprues on the sidewall of the tire (the small rubber hairs from the tire molding process). The same leaks are not present on the molding sprues of the front tire. Does this sound like a manufacturing defect, or could it be fixed with some fancier sealing compound?

Sounds like a defective tire. The rubber has not fully filled the mould at the injection point.

Don't mess around trying to fix it. Take it back to the bike store and have them swap the tire for you. That way you'll know you have a good tire that will not fail on you later.