For a while now, the tyres on my car have been absolutely dreadful. They're constantly deflating, which means I constantly have to get covered in tyre dirt to inflate them again.

They're Avon ZV5 tyres, 195/65/R15 (91V) TL tyres. They're on a 2003 Seat Leon S.

The reccomended tyre pressure (by Seat) is 33 PSI. I inflate them with a crappy electric air pump (the pressure gauge is buggered, so I confirm pressure with a Halfords tyre pressure meter)

Within a week, the pressure can drop to 30 PSI, and I checked today and they were down to 25.


What's going on? One of the tyres is literally 3 or 4 months old, and it's decreasing at a similar rate to the others. They've been checked, MOT passed, etc.


Any advice?

Cheers

I think they water tested some of the wheels, and one of them is a few months old. It maintained its pressure for about a month and then started to decline like the rest.

The wall of the tyre looks just fine to me. As do the alloys.

As it's all tyres, I would suspect the alum. alloy wheels. Over time they can oxidize, and start slow leaks around the tyre seat and/or valve stem seat. Even more likely if they were re-tyred without properly cleaning and polishing the seating areas.

Try a 'soap test'. A few of squirts of liquid dish soap in a liter of water. Use a spray bottle or a rag to wet everything down and, over time, watch for bubbles to grow. Even very slow leaks can show up with this method. Pay particular attention to rim edges and around the valve stems.

You can also check  Ozzy'z theory by squirting some in the valve cores. If that turns out to be the problem; tighten the valve cores.........and give the ball back.