Tyre losing pressure

[Scylax]

My Honda Jazz, with only 3000 miles on the
clock, has a brand new tyre fitted to the rear
offside wheel.

This tyre, unlike the others, keeps losing its
pressure ; about 2 or 3 psi per day.

Two separate tyre companies have examined it,
and report that it's perfect - no slow puncture,
no valve defect, nothing. But it isn't perfect; it
keeps losing air. What on earth can I do now ?

[McNoodle]

Have they checked the rim, and the seal between it and the tyre?

[Scylax]

'Tis a thought, McNoodle.

Tomorrow I shall take the car to a third independent
tyre specialist and specifically ask that the rim and
seal be examined, critically.

I don't want to buy yet another new tyre because,
with my luck, it would leak air, and no-one will give
me a cast-iron, money-back guarantee that it won't.

Thanks for the suggestion, Mac. Here goes.....

[Toureman]

Older garages have a tank to immerse the wheel and tyre in, this is the only and best way of finding where the leak is, It,s no good just examining it.

[McNoodle]

'Tyres' don't leak - unless they're punctured. Air is escaping from somewhere and there can only be four possibilities - puncture, valve/seal or stem, seal between rim and tyre or in the case of alloys a cracked rim.

[Scylax]

Eureka ! Third time lucky......
3rd. tyre company spotted a pinhole puncture
by immersing the whole tyre in a water tank, as
you suggested Toureman.
Oddly enough, at 15 lbs. psi there was no sign, but at 30 psi the bubbles became evident. The repair was
easy and successful. Magic.

Many thanks for your interest and replies.