My son started riding his bike this weekend without stabilizers, he was 5 in Jan. With him it was more a confidence thing but the last couple of weeks I have been taking him to local indoor skatepark in Stourbridge because he has always loved his scooters. The confidence it has gained from using the ramps etc on his scooter has transferred to him riding his bike, now from going up and down a path on Saturday to being able to turn around without stopping on Sunday to riding his bike all over the place. If I knew about balance bikes when he was a few years younger I would of brought him one( I discovered how they could help from this forum). My little girl (2.5) has one of the chillifish trikes that convert into a balance bike. I switched it to the balance bike because he complains being too big for the trike, she was pootling about at the skate park but the balance bike was a little too small for her so I have bought her balance bike yesterday and she has been riding around on it all day yesterday chasing after her brother without any issues.
Now my son has started the riding without stabilizers, there is a downside. He his tall for his age so he his at the very limit of his 14" bike and now wants BMX and fits 18" bike nicely which means he will be getting a new bike this week and its not even Christmas or his Birthday!