Why do bicycles have the back brake on the left hand side?

The common suggestion is that the arm is important for signalling when you are going across traffic and the rear brake is still controlled. So for countries that drive on the left (UK) that would be your right arm signalling, and left hand controlling rear brake. read more

As noted, the front brake does most of the stopping, and the idea that you will “flip over” is essentially nonsense if you practice proper stopping technique (sliding your weight to the rear) just a little. read more

Since the front brake is the one that actually stops you faster on a high speed run (the rear just makes the bike skid), mount the lever on the side of your most skilled hand. So, if you are right-handed, mount front brake lever on the right, rear on the left. read more