My daughters recently purchased mini one had a N/S front wheel puncture last night, luckily she was on local roads so she was ok. She said she had heard a rumbling noise from the front wheel just before she had the puncture. On taking the wheel off, there was a deep ridge cut in to the tyre, going right around the inside of the tyre, just where the treads ends and it appears that this was the cause of the puncture, but I have no obvious clue as to what has caused this damage, can anybody on here help?