I will sound a bit thick but i'm no bike mechanic, to give you an idea of what make my bike is here are some pics (the bike isn't mine and the owner doesn't know).
the problem is that I cannot get the valve caps off I tried twisting and pulling, pliers are a no no due to the bike not being mine, here's a pic, any help is appreciated, Thanks.
Quick edit Just to clarify I've not stolen the bike, I crashed mine and it's the beginning of summer and I really wanted to ride, the bike is my mother's and just needs some maintenance. Also I appreciate the answers I've tried using more force but the entire valve seems to turn and jam, no movement on the cap. Any ideas?