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Emergency Braking Practice Speed
30 MPH is as realistic as is 60 MPH

By: James R. Davis



A very interesting question was asked by a new rider on my site: How fast should I be going when I practice emergency braking?

I suppose that many of you, like me, average speeds in excess of 60 MPH while we are riding and I also suppose that you might believe it is necessary, therefore, to practice emergency braking at a similar speed in order to make it 'realistic'.

Absolutely NOT!

Despite how fast a motorcycle can theoretically decelerate (very near 1g, or 32 ftpsps), *YOU* and your bike are more likely to be able to stop at a rate no faster than about 29 ftpsps or 20 MPH/Sec. That's about .9g's and beyond the ability of probably 90% of even the most experienced of riders.

Why is that important to know? Well, the fundamental risk to you as a motorcyclist when doing emergency braking is that you will lock your brakes and fall down. Locking your brakes, alone, is not particularly dangerous, but doing so almost always results in losing the balance of your bike and shortly thereafter its 'footing' - i.e., you dump the bike.

Another thing about the ability of well over 90% of even experienced riders is how short a time they can balance a bike. If your bike is at a dead stop, how long do you think you can keep your feet on the pegs before you must put a foot down to save the bike from falling over? For the vast majority of us it would be about 1 second.

If it takes longer than 1 second for you to stop a moving bike, in other words, then you cannot rely on balance alone to keep you from dumping that bike if you make the mistake of too aggressively using your brakes and locking it(them).

In fact, when you lock your brakes it takes some time before the bike ceases to be vertical - because of a slide (to the side) of a tire or other steering input. Only then must you try to correct the problem using your sense of balance. So, if you lock your brakes, perhaps 1/2 second later the bike is no longer vertical and about 1 second later you are on your side.

Let's put all of that into a coherent picture.

If you are close to maximum efficiency with your brakes, and use both of them, when moving at 20 MPH, you should be able to come to a complete stop in approximately 1 second. If you are too aggressive with your rear brake and lock it, then it will take you slightly longer than 1 second to come to a complete stop. But so long as it does not take you 1 1/2 seconds to come to that stop you will do so while still on your wheels. Any longer and you will likely come to a stop with the bike on its side because it will have fallen over.

The objective of emergency braking practice is to find how close you can come to a skid without actually causing a skid - that is, without locking a brake. So, in order of likely outcomes, during practice you will neither brake at the theoretical limits of the bike's ability nor will you lock your brakes, you will lock your rear brake only, you will lock both brakes (a very unlikely event while practicing), you will brake at the bike's limit. If you lock only your rear brake then you are likely to fall over if it takes longer than 1 1/2 seconds to come to a stop.

At 20 MPH, in other words, there is almost no chance of falling over before you come to a complete stop (and even if you do you will collide with the pavement going approximately zero MPH.) At 25 MPH you have reached a speed at which making a mistake in your braking (too aggressively using the rear brake and locking it) can result in you ending up falling over before you have come to a complete stop.

At 30 MPH you are tempting fate. Meaning, it is now dangerous for you to make a braking mistake.

Thereafter, meaning at any higher speed, the danger to you increases.

So, doing emergency braking practice at speeds up to 25 MPH is essentially without serious risk to you, and doing those practice sessions at 30 MPH is REALISTIC in the sense that you are clearly at risk if you do it wrong. But doing those practice sessions at any speeds higher than 30 MPH is both unnecessarily dangerous and no more realistic than if you do them at 30 MPH.

By the way, the reason that the MSF 'got away' with having their students do a rear brake locked skid to a stop exercise was that they did not allow their students to do so at speeds greater than 20 MPH. No deaths occurred and very few dropped bikes - and those drops occurred at about zero MPH. (AGGRESSIVE USE OF THE REAR BRAKE IS NEVER 'REASONABLE' OR SAFE and the MSF has finally learned that having students do it was irresponsible so they no longer do.)


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http://www.msgroup.org

(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)

     
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