Bicycle Stem Headset AirTag Mount

I travel far on an overloaded cargo bicycle, and for the first ~50,000 miles, its stem cap was an electronic analog clock, which is to say, I’m old enough to still be an analog guy. But that clock quit working about 15,000 miles ago, because I travel in all four seasons through all varieties of weather, and — who knew? — electronic analog bike-stem clocks don’t like getting wet.

I’d been meaning to replace it, but I’d gotten used to having a stem cap that wasn’t just a stem cap, you know. So I was searching for another sacrificial electronic analog stem clock — the old one lasted years, after all — when I noticed this option, and it too is more than a stem cap. But this one serves a function I need a lot more than an analog clock. After all, there’s a bike computer on the handlebars, and it shows the current time in digits, plus much more, and I’ve also got a watch on my wrist.

But an AirTag secured in a weather-proof housing to the stem of my bike? Yeah, that I need.

Installation was as easy as the old analog clock, which I had to remove annually to replace its button battery. The AirTag even uses the same ubiquitous 2032 battery, and I always have a few of those in my backpack. Apple says the battery can last up to the same full year in the AirTag, so all that will have changed for me is that I’ll no longer be staring at an analog clock that’s only right twice a day.

This AirTag stem mount is deceptively simple — just three parts: (1) The base that accepts the included (2) countersink bolt and is capped by a threaded, well, (3) cap. I could have machined the two housing halves from Delrin using a lathe, but that would have taken a full day of trial and error, would cost me almost as much in material, and I’d end up with something not nearly as refined as this inexpensive, off-the-shelf, purpose-designed solution.

Is it indeed weather proof? I haven’t tested that aspect, but I suspect, yes, it is. The threads that join the two halves are exquisitely fine and mate perfectly. The male threads are on the base so are covered, thus shielded, by the female threads when in place, which forms an effective drip ledge. Sure, water would eventually get in if it was submerged, but if the bike and I go under, I’ve got bigger problems than a dead AirTag. But rain? Yeah, that’s not getting in.

How does it look on the bike? Kind of great, actually, as stem caps go. But I doubt you’d notice it, because its color matches the black spacers underneath. And that’s the point. If I need that AirTag, it won’t be because I forgot where I parked the bike. Okay, someday that might be the case, but today, it’ll be because some rat-so-and-so stole my bike, and if that happens, I’d prefer they not notice the stem cap sporting an AirTag. At least until the police and I get there and show them how we found them.

If you value your bike and its stem accepts this style of cap — and you do, and it does — you need this. Oh, and in case you’re wondering, I’ve hidden a second AirTag on the bike, but I’m not going to share where.

Hope this helps. Clear skies!