Question: Why do you balance better when you are going fast on your bike?

Susan Cartwright answered on 22 Jun 2015:

Basically, you balance on a bike by making small steering motions to counteract any lean that develops – so, if you feel yourself leaning to the left, you steer slightly to the left to get the bike back underneath you. This is easier when you’re going fast, because just a slight steering motion will be enough to move the bike where you want it, whereas if you are going slowly, you need to make more exaggerated steering corrections to do the same job.

Of course, once you’ve learned to ride a bike, you aren’t making these small corrections consciously – it’s all automatic.

It used to be thought that the bike’s wheels acted as gyroscopes, and the faster they spun, the more stable they were. There is such an effect, but it turns out to be small. A chap called David Jones actually built a bike with a second, inner, front wheel that rotated in the opposite direction, cancelling out the gyroscopic effect, and found that it rode pretty much like a normal bike, though it was very unstable without a rider (so the gyroscopic effect would be important without the stabilising effect of the rider’s weight). Jones tried several other designs of “unrideable bike” – his best effort was one that had its front wheel moved about 10 cm forward of its usual position, which reduced the self-centring (the tendency of the front wheel to come back to the straight-ahead position when released). He writes of this bike, “It was indeed very dodgy to ride, though not as impossible as I had hoped – perhaps my skill had increased in the course of the study. URB IV had negligible self-stability and crashed gratifyingly to the ground when released at speed.”

Obviously, it is not in the interests of bike designers to produce unrideable bikes! So the design of the modern bicycle is intended to make balancing as easy as possible.