[Carriage Hill]

I remember back in the late 50s, when my Schwinn Black Phantom went down our street for almost 2 blocks before it fell over on to a lawn. Still can’t figure that one out.

[doorgunner69]

Gyroscopic forces kept it upright. A lot of trail on the front wheel helps.

[Vermont Lt]

An object in motion will remain in motion. Unless it falls over.

[Svartalfiar]

I remember back in the late 50s, when my Schwinn Black Phantom went down our street for almost 2 blocks before it fell over on to a lawn. Still can’t figure that one out.

Like doorgunner mentioned, gyroscopic forces help it stay up. A running motorcycle wants to stay upright. Try taking the bike out, and start trying to tip over. Once you hit a certain speed, you'll turn but the bike pushes you back upright. if you just relax and let go, the bike goes mostly straight.