Flat tire but no leaks?

Thats a strange one, have you kerbed your wheel and maybe there is a gap or something? If not then there is obviously some leak within the tyre somewhere, or its fitting badly to the wheel for some reason. Give them some stick until they fix it!

Mine was doing something similar, i thought i had a puncture but when i took it to the tyre place (a back street type thing not a dealer) they couldn't find anything wrong with it - no leaks when they put it in the water bath thingy.
Anywhoo the chap was saying sometimes you can only get it to leak air when the weight of the car is on it. He took the tyre off put some kind of sealant round it and put it back on the wheel and its been tip top oh and it cost me £4.
I've got Pirelli 17" run-flats on S spokes

I had the same problem with pirelli runflats on my 04 MCS, it's because the sealant around the inner edge has broken (probably cornering a little too fast - the hard side walls of the runflat, break the seal! They sometimes only let air out when cornering. They simply need re-fitting!

MattJCW said:

I had the same problem with pirelli runflats on my 04 MCS, it's because the sealant around the inner edge has broken (probably cornering a little too fast - the hard side walls of the runflat, break the seal! They sometimes only let air out when cornering. They simply need re-fitting!

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That may be the case. These are brand new tires I had put on by the dealer 2 weeks ago. The problem is the dealer won't do anything about it. They say they can't find the leak so everything must be fine. Now they're just sitting on the car taking pressure readings every day. I've told them that they should drive the vehicle but they won't.

Not sure what else to do.

One of the reasons I got away from the runflats. They're too finicky. The tire needs to be remounted. The bead where the tire meets the wheel did not seal fully. A good tire dealer with the proper equipment should be able to fix it for you.

I have had a similar problem with non runflats. The tyre dealer said that I needed to get my alloys refurbished because they were leaking round the rims. I put up with having to inflate the offending tyre on a weekly basis for the duration of its life (which wasn't long thankfully!). I got a new set on and they don't leak at all! I think that they just needed to be taken off and put back on again to see if they seat better on the rim.