Why is my tyre deflating!

what type of rim is it , how old is the rim

Have them swap the tyre onto another wheel. The problem may follow the tyre but I suspect you have a porous alloy wheel or similar.

It's probably leaking from the rim, fine when in the bath, but once there's the weight of the car on it....

I have a "dodgy" tyre on the rear of my car at the moment, it's fine 95% of the time, but sometimes when I get to it in the morning it's 1/2 flat, seems to be only when it's left overnight with the tyre at a certain position. I can live with it until I replace both rears in a month or so, 'specially as I have a rechargable compressor in the boot ;)

If it's an alloy, corrosion around the bead seat. Get them refurbished and the problem will go away. I was losing 10psi a week from one of mine until I got them fixed.

If you're anywhere near Hemel Hempstead,

if its alloy it could be porous , steel may have a small rust hole , these holes wouldn't show up in a water test unless the whole wheel was immersed and possibly a load applied

get some gas detection fluid from a plumbers merchants apply over the wheel rim

Have not got alloys, therefore can ordinary rims be repaired and if so is it a cheap job?

Hi Tony, thanks very much for taking the time to reply. I do not have alloys, therefore if it is leaking from the rim, how can a test be done on it to simulate the weight of the car? Can the rim be repaired? Is this the sort of job any tyre fitting company could do or is it a specialist job?

If they're not alloys, and it's not a new car, I'd try getting a spare[1] from a scrappers. They're usually like new with a decent tyre on...

Steel wheels can also corrode on the bead seat area. I have 'repaired' them in the past with a wire brush. I had planned to then paint the area if that did not work however that proved unnecessary.

Clearly you would want to wait until the paint was completely dry before re-fitting the tyres to make sure that they did not get glued to the rim.

I recommend a scrap yard wheel.

How about a tube?

Steel wheels can also corrode on the bead seat area. I have 'repaired' them in the past with a wire brush. I had planned to then paint the area if that did not work however that proved unnecessary.

Clearly you would want to wait until the paint was completely dry before re-fitting the tyres to make sure that they did not get glued to the rim.

I recommend a scrap yard wheel.

How about a tube?

Whenever I've had a tyre repaired or replaced and the rim is a bit s***ty I've seen my local tyre fitter use a grinder on the rim and paint it before fitting the tyre.