Comment by bityard
Training wheels are terrible. Both of my kids learned how to ride on balance bikes, basically in under a day. When switching to pedal power, there IS a transition period where learning how to pedal AND balance at the same time is challenge. But it's a lot shorter and less frustrating than trying to learn how to pedal AND balance at the same time.
Agreed. We didn't get onto the balance bike tip until my older kid was a little older, but my younger one started on their older sibling's balance bike as more-or-less a toddler and was riding a bike with pedals by age 4. With basically zero frustration.
Watching peers of theirs who used training wheels, I've realized they're a trap. The mechanics of how a bike actually steers are completely different when you put training wheels on it. Whenever a third wheel is touching the ground (something that seems to be hard to avoid while turning, from what I've seen) it starts to steer like a trike instead of a bicycle. So transitioning from that to riding without training wheels is doubly difficult, because you also have to un-learn the instincts and muscle memory you developed with training wheels.
Transitioning from a balance bike to one with pedals is much easier because the main instinct they'll be taking from it - putting a foot on the ground when you get into trouble - remains useful. It naturally helps prevent skinned knees during the transition period.