I run mine at 26f 26r solo (26f 33r when towing 1.6T with 2 people, 35r with 4 people or an extra load).
For many years I've used a test recommended to me by a well-known tyre company & it frequently has confirmed the car manufacturers figures are correct (but not always LOL). Make sure the tracking is correct as this can cause higher pressure increases.
After setting the tyres cold (first thing in the morning preferably: before use, not after driving to the garage!) run the car for at least 30/50 miles in order to thoroughly warm-up the tyres. The increase in pressure to be aimed for should be 4/6PSI. If the increase is [B ]too much[/B] then cold pressures are too low (tyre is overheating), if the increase is too low then cold pressures are too high.
The only draw-back is that pressures can get much higher if the ambient temperature varies dramatically eg. tyres set in this country then driven abroad to somewhere really hot. But used intelligently I have yet to fault it over many years use.
It's a bit of a pain to do properly, but it only needs doing once!
