Had a visit to my local tyre supplier today thinking i had a screw in the middle of my front N/S  tyre .... lol but being a lexus noooo not that simple . Bloke had a look and said it was my valve leaking air right at the bottom where it fits in the alloy wheel. He said there should be a small round piece of rubber or metal missing ? Is this true and can it be sorted ... Appreciate the help thanks 

Surely that's just the valve itself and a new valve will sort it? Unless you have TPMS in which case a new valve will still sort it but it'll be more expensive.

Before the advent of TPMS, valves used to be changed as a matter of course every time the tyre was changed.

Hi Herbie ,

Thanks for your speedy reply as far as i saw today i dont have tyre pressure monitoring system on my rx .. just valves... i have never heard of this before and he did fit a new valve which still leaked air ... he said i need another alloy wheel ,?????? 

It could be that there's some corrosion around the hole that's not allowing the valve seat to seal properly, in which case you could get the wheel refurbished.

Other than that mate, I'm afraid I don't know.

The wheel did look a bit grubby and to be honest they could do with being all refurbished... will look into that thank you Herbie