I have a slow leak in one of my tires. It takes about a month to drop 15#. The tire place I go cannot find a leak and insist it is not leaking. I am trying to figure the approx frequency of bubbles it would produce if submerged in water. I can’t seem to find an accurate way of determining how much air is in an air bubble. I would think the bubbles should be pretty much the same size, How can I determine how much air is in an air bubble?
I don’t know the bubble answer, but have you/they tried over inflating the tire and looking for leaks?
ETA: Although I’ve had success overinflating and looking for bubbles, for all I know there is danger in doing it.
I don’t have an answer to your question, but I do have some advice:
Take your car to a different shop. The one you’re going to now hasn’t found a leak, which is understandable, but they shouldn’t tell you there’s no leak at all. There clearly is a leak if you’re losing 15 PSI a month. A different shop might find the problem. If they do, take your business there from now on.
Also, if you want to look for a leak yourself, one way is to spray soapy water on the tire and watch closely for new bubbles to form. A slow leak like this will take patience and a sharp eye. Be sure to look not just at the tire tread, but also around the rim. Take the valve cap off, put some soapy water in the valve and watch for bubbles. Look around the base of the valve.
I would suggest finding another tire place if they can’t find a leak. I found a leak in a tire of mine by using some soapy water. A few squirts of dish washing soap and some water in a spray bottle. Spray the tire concentrating on the bead area and the valve stem. The smallest of leaks will produce bubbles. In my case, it was a loose valve stem valve. Tightened it and my leak went away.
The tire might not be seating well around the rim and only leaking when the vehicle is in motion. Could have your tire place (or a different one) dismount and remount the tire and look at that. As your tire flexes when going around a corner it can pick up dirt or a small rock in the seam.
I actually did remove the tire and clean the seating area and replaced the valve stem. It seems to have fixed the problem 4 days so far. But I am curious about the air bubble.
Ok, here’s some math
Assume the tire is 50 liters volume
Pressure is 2 atmospheres, so you add 100L of air to the tire to inflate it
You lose 50% of that air in a month, that’s 50L or 50,000ml
Divide 50,000 by 30 days, 24hrs, 60min and 60sec ,and you get 0.02ml lost per second, or about 0.2ml lost in 10 seconds. I figure that’s enough flow to be noticeable when submerged in a tank, or when covered with soapy water.
How much air in a bubble depends a lot on where it is formed, some bubbles are harder to dislodge than others, so they need to be bigger to float free.
That’s what I’m finding is that air bubble sizes are not consistent depending on how hard they have to pull to release