Newbie on this forum so apologies for seeking advice so early. Just bought my son a skinny hybrid no brand fixed wheel. Lovely bike for getting him to school and work. He got a puncture within 3 days so tried to fix it. All my patches were too big and I got frustrated and went to buy a new tube. The old tube had no identification on it so I took it to my local bike shop. They sold me a 700/18. This is fine but the tyre around the valve protrudes and doesn't sit right. Is there a different tube for these new fangled deep rims? Thanks for any advice, a frustrated dad!