Back seats till age of 10 Bobike bicycle safety seats for the back of your bike are suitable for children till the age of 6 years or with a body weight not exceeding 22 kilograms. Bobike Junior seats are suitable for kids ages 5-10 years or with a body weight from 20-35 kilograms. Your child ‘moves’ to the back because a sibling was added to the family or because it became to heavy for the front seat.