I was like many of you for quite some time. I used the rear brake to trail brake, keeping the rear aligned with the front. Some of my racer friends told me time and time again to stay off the rear brake but I had been riding motorcycles longer than some of them had been alive. I knew how to use the rear brake and I did not listen.
However, on one warm October day a few years ago, I was on a Hayabusa only three months since brand new. I was having a blast on a twisty back road when I came up a long straight stretch which turned into a pretty tight right handed corner. I got on the front brakes hard to burn off as much speed as I needed to enter the corner safely. As fate would have it, while on the front brakes hard and the bike standing straight up, I gave the rear brake a little nudge, just a tiny one and instantly the rear steped out to the right. What I should have done was let go of the front brake and maintained a little rear brake but my instinct told me to let go of the sliding rear tire which I did. That puppy instantly went into the tank slapper from hell, ripping the bars from my hands with evil intent. The bars went from side to side hitting the stops on both sides so fast it sounded like a chatter and from the time I let go of the rear brake until I was airborne in the horizontal position about eight feet off the ground was less than a second. I hit the pavement at somewhere between 70 & 80 MPH and from there it was a race to see which one of us (The bike or me) entered the woods first? Well, it so happened we both arrived about the same time. When the dust settled, I felt everything to make sure it still worked and no broken bones. Once I sat up and looked for the shinny new busa, I could see busa parts scattered down the road for a couple hundred feet or so and there lay my prized busa all twisted up like a pretzel. Just not much left of her since she went the distance end over end.
So the moral of that story is, before that crash I had the attitude like many of you, if the rear brake wasn't meant to be used there wouldn't be a pedal on the right foot. Now days, I ride with my toe on the foot peg so I can't get to the brake pedal even if I'm temped to do so. I learned my lesson the hard way and at least some of you nonbelievers will eventually learn the hard way as well.
Slow speeds around town, the rear brake will not threaten your life but when you are twisting the throttle and have the wind buffeting the back of your jacket, if you are wise you will leave the rear brake alone. If you are foolish enough to stand on the front brake at speed and thing the rear will help you keep her under control, keep your health insurance premiums paid. It's in your best interest.
Attend one of Mike Sullivan's Race Schools and he will do his best to hammer home the point of "Stay off the rear brake". Mike Sullivan is Probably the fastest guy in the state at age 48 and been racing motorcycles since kindergarden. Mike says the number one cause of inexperienced riders crashing is the use of the rear brake!
I you know how to use the rear brake like many racers do to step the rear out when entering a corner and keep it spinning through the corner, great! If you can't, you'll be wise to stay far away from the rear brake when you are riding hard.
If you still have doubts, just take your prized busa out on a nice lonely back road and run her up near tripple digits and stand on the front brake as hard as you can and once the rear is skitching from lack of traction, tap the rear brake gently (It only takes a slight nudge) and see what happens. As long as the rear wheel is touching the pavement an rolling it will stay behind you but if you touch the brake with little to no traction on the rear, it WILL instantly lock up and you are most likely going for a ride you won't soon forget