I've got a Lreg V6 Calibra which I've had for over 10 years now. It's a great car, but the one recurring problem has been the stoke alloy wheels deflating. Sometimes slowly, and other times really rapidly. I've had new tyres and valves fitted, but the problem persisted. I'd have the sealing surfaces wire brushed to remove the flaky lacquer and paint. Which would fix the problem for a while, but then within a few months it would start happening again.
I took my wheels to a local tyre shop last year, and they finally fixed the problem. The mechanic used an angle grinder instead of a wire brush, and sanded down the sealing surface on each alloy. He removed all the old lacquer and paint, and just left a lovely smooth clean metal sealing surface. Since then I've had no problems.
He only charged me £5 per wheel.
I wish I'd known about this simple solution years ago. It would have saved me so much hassle. Hence this post.