Q I just got new tyres a few months ago, but since then one of them has been going flat regularly. I had that one checked out where I bought the tyres, and there aren’t any holes in it, so I’m perplexed. How does a tyre with no leaks go flat?
A This sounds like a riddle: How can a tyre with no holes go flat? By not leaking through the tyre, of course. Just because the tyre itself is fine doesn’t mean there aren’t other avenues for air to escape.
Two prominent possibilities are the valve
stem and the wheel on which the tyre is mounted. Usually, a new set of tyres includes new valve stems, since they can go
bad through use and from exposure to road chemicals. If a valve is bad, you’ll have a constant and very slow leak through the base or the valve body.
The other possibility is that the mounting surface of the wheel where the bead of the tyre seats has become damaged by
corrosion or dented from hitting a pothole. To see where the problem is coming from, fully inflate the tyre and dribble a mixture of dishwashing liquid and water onto the valve stem, around its base, and around the inside and outside edge of the wheel where the tyre and rim meet. Any escaping air will produce bubbles in the soapy water at the site of the leak. Then you can take the tyre to the workshop where you purchased it (which is where this leak should have been diagnosed in the first place), knowing exactly what and where the problem is.