I had to throw out six ounces of fresh Stan’s, but at least I identified the most-likely cause of my road tubeless issues: the rim tape. For some new wheels that I’m building for the Vaya, 1/2″ tensilized polypropylene strapping tape (McMaster-Carr part number 7637a31), which seems to be the same as Stan’s NoTubes 12mm tape, was chosen for sealing the rim. This width covers the spoke holes, but after being pumped up to 70 PSI it seems to have leaked as the tape stretched.
The photo above shows where the tape slightly puckered and allowed air (and sealant) out when under high pressure.
The proposed solution for this issue is a double-layer of tape, partially off set side to side, to both make the area over the spoke holes thicker and have more tape stuck to the inner wall of the rim (photo). I would have used a wider tape, but the next size up is 21mm, and this doesn’t sit nicely in the U channel in the center of the rim (cross section).
