Inspired by this thread, I checked the rubber on my Yam 900 Diversion - Bridgestone Battlax BT021s. The rear says that maximum load is (x) lb at 42psi, which ties in with what has been noted here previously; that what is stated in this way is not the maximum pressure the tyre will take, but the pressure at which it can support its maximum load - presumably at up to its maximum rated speed. Since the pressure in the rear tyre after a period of high-speed riding will be around 10percent higher than 42psi, this cannot be its maximum pressure rating. FWIW, cycle tyres have a max. pressure rating moulded on the sidewall, but that's 'cos a narrow clincher inflated to 160psi might either blow clean off the rim or, if the rim is worn, break the rim by cracking the sidewalls away at the braking surface. It is invariably way higher than the highest recommended riding pressure. I run 36/42 on the Diversion in all circumstances. The manual says this is right for for two-up and high-speed riding and says 33/36 otherwise but, since I never know when I might venture onto a fast stretch of road, I prefer to stick with 36/42 day-to-day. In any case, there's enough grip in the dry to scrape the footpeg hero blobs and reach the edge of the rear tyre tread. Also, the higher pressure reduces the bike's tendency to self-steer in road depressions. For solo riding I have tried 33/36 and 37/43 pressures and even some in between; why not experiment a bit to find the exact pressure that suits? Off-road? Yup, I air-down, albeit not as much as some suggest here but that's 'cos I hate the idea of a pinch flat. Still makes a big difference to grip.