Re: Tyre pressure how much?
There's probably a sticker around the driver door for recommended tyre pressure and most tyres have the imprint on the side that dictates the maximum pressure designed for. You can check them out and use them as a guide. Most tyres will falls within the range of 220 ~ 260 kpa, with 220 on the comfort and 260 kpa being more hard on the ride but in some performance tyres, the higher pressure is needed for optimum grip.
Hence, besides the rims' size, it also depends on the type of tyres you have bought. What you basically need to look out for is that the span of the tyres contact squarely to the road surface, you will know that you are riding on too little pressure when you both your outer edges wear out faster than the centre. Likewise, your center will wear out faster if you have over inflate. Both these conditions are bad as it's easy to aqua-plane in the former and poor grip for the latter.