Monday evening - swapped a tyre over on SWMBO's 2cv - big nail right through the tread, so no doubting there was an issue. Whilst I'd got the compressor out, I went round the other cars and checked the pressures. Including the spares (first time in ages, I will admit) - the Saab spacesaver was down to ~20psi from the 60 it should've been.
Tuesday evening - one of the Saab rears was extremely soft - still holding the rim off the ground, but barely. On with the newly reinflated spacesaver.
Weds evening - get round to checking that tyre, now completely flat. Nothing in the tread to cause a problem. No sidewall damage. Valve looks fine. Reinflate it.
Thurs am - Oh, look - it's still at full pressure.
I _hate_ things like this. Will I go out there this eve and it be flat? Will it suddenly have a sulk and go flat half way down a back lane on a pissing wet night?
If something's going to give me s*it, I'd rather it gave me CONSISTENT s*it...