Hi
my kids new bike arrived and it almost ended up in a huge crash for him. The bike going downhill just started wobbling uncontrollable. Luckily he slammed the back break on and avoided a crash.

​​​​​he was doing about 12mph and wasn't messing about.

The bike is new and has spoke reflectors so am wondering if there is a way to try and balance the wheels on his bike.

Thanks