What tyre pressures should a trials bike have?
Front: 0.5bar (50kPa)
Rear: 0.3bar (33kPa)
Naturally, this is average. If you are riding on sand, mud or low traction surfaces, you can go lower than that. If you are quite heavy, riding rocks and hard edges, or generally hard (aka a bit clumsy) on a trials bike, increase the pressure slightly to protect the rims.