Why does nobody talk about the right way to check a tire for a slow leak?

I keep seeing guys at my hangar just spray soapy water on a tire and call it a day if they don't see bubbles right away. In my experience, that's a good way to miss a leak that shows up only when the tire is under full load. I had a Cessna 172 last month that kept losing a few PSI a week. We soaped it cold, nothing. I finally put it on the jack, loaded the strut with weight to simulate sitting on the ground, and inflated to the full spec pressure. Found a tiny seep right at the bead seat after about ten minutes. If we'd just sent it, that tire would have been a problem on a hot day. It's a five minute extra step that matters. Has anyone else run into this, or am I just being too careful?

3 comments

3 Comments

irisjenkins17d ago

Good point, but you don't need to load the strut. Just jacking it up to take the weight off the wheel lets you check the whole tire and bead evenly.

jennys727d ago

Oh wow, that's a solid back and forth! @irisjenkins is right about getting a clear look at the bead, but reesemoore has a point about finding shoulder leaks. Honestly, I'd just check it twice to be safe. Do a quick soapy water spray with the wheel off the ground for the bead, then lower it and check again with the car's weight on it. You cover both possible leak spots that way without any guesswork.

reesemoore17d ago

Forget the bead for a second. If the tire's got a slow leak from a nail in the shoulder, you won't see it bulge right when it's unloaded. You need the car's weight on it to push the puncture open so the soapy water bubbles. Jacking it up hides that kind of leak.