WaaHuw

Hi, just recently purchased a 09 onza rip. It came with some rubbish cheapo tyres on it (probably going to upgrade) I'm interested to know what tyre pressure to run as I have no experience in this erea of mountian biking. I let out some air today whilst I was messing around, but I think I let out to much becase when I was balancing on pointy ledges, my tyre hit the rim. I only weigh 40kg, so I can't get any other guides because everyone else is heavier than me. Thanks for all help given!