just got a little tip for all you new riders out there or even some of the older ones. if you have a problem with thorns and stuff giving you punctures, but you dont want a dfferent tube because then you will get loads of pinch flats. buy a heavy duty tube and a tube thats good for preventing pitch flats. get your heavy duty one and cut the valve out and stick it to the opposite side to the tyre tread (inside).then put your other tube in as you would usually. then you have the tube with no valve to stop most thorns geting though and a tube to stop you getting pitch flats. dont have to do this in both wheels just the back really. add replys if you thinks this is a good or bad tip Callum Hicks