One problem with inserting a tube is that it doesn’t always place nice with the tire. Once I had no problem, but two other times I did. The first problem time it took me a couple of tries to get the tire seated correctly. The second time it wouldn’t. The valve stem attachment caused a bubble/wobble in the front tire. There just wasn’t enough room for it. Fortunately I was only about 6 flat miles from my car, so I rode back slowly.