Air Might Go On The Inside

When we last left off with our tubeless adventure, I thought I might have, maybe, got things figured out.

Well, then my front tire went flat while it was sitting out in the sun, drying off after being hosed down, much like it had been on Friday when the rear tire went flat.

I did a little thinking a little hummin' and hawin', and decided to retape the front rim too.

While I did so, though, I made sure to pay special attention to the condition of the tape as I removed it, since I had a little suspicion that there might have been a problem with the way the rim was taped.

For reasons of supply chain issues, the rim was taped with two wraps of a narrower tape rather than a single wrap of a wide tape. While this did indeed result in the spoke holes being covered by the tape, along with the rest of the inner rim surface from bead to bead, it did mean that there wasn't a single piece of tape that spanned the entire spoke hole.

These spoke holes alternate slightly from side to side, so on most of them you'd have about 75% coverage with one wrap of the tape, and something very close to 100% coverage with the other wrap. Sometimes it'd be a little more than 100%, sometimes it would be a little less.

In the image above, you can see what happened when it was just a little bit less: the unsupported edge of the tape stretched, air and sealant got between the two layers, and then spilled out through the spoke hole.

Here's another example.

On this one, the top layer of tape was covering about 75% of the hole while the bottom layer was covering maybe 99%, still enough of a gap there to allow the air out once it had worked its way under the unsupported edge of the tape. Not good.

As a comparison, here's what it looks like when the tape didn't lift at a spoke hole.

No sealant leaking under the edge of the tape, no air leaking out the spoke hole. If they all looked like this, my tire wouldn't have gone flat.

So I think, and hope, that this should settle the matter. I taped up the rim with the new rim tape, much like I had done for the rear, and so far it's holding air. With any luck that trend will continue and I can finally put this issue behind me.

I do want to add that I'm still reasonably sure that the valves and the taping and parting line flash near the valve hole were also contributing factors. It's really hard to say if there were multiple failures or not, as it's almost impossible to directly observe where a leak like this is occurring.