Philip's Ravings

Emergency Braking is a contentious discussion topic. Many people have different views - and often they are all right - in certain circumstances. Often views vary from country to country as different methods are taught, and people like to (rightly or wrongly) defend what they have learnt and practised over the years.

What is emergency braking?
Emergency braking is the act of bringing a motorbike to a complete halt in the minimum amount of distance.

Overview
Often when a country develops an emergency braking training philosophy based on method "x" it is because they have to develop a single consistent message that they can teach to every rider on every road going bike. That method has to be based on the mix of the motorcycle fleet in their country, and so may not suit another country as a result. And I sympathise with them to some degree - that is about the only way you can teach something on a national scale.

My personal opinion is that the required technique for emergency braking depends on the rider and the bike involved. For example, classic bikes can have front drum brakes while modern bikes nearly always have disc brakes. This changes the time to transfer the weight onto the front tyre drastically. And even newer bikes have ABS and/or integrated braking. Integrated braking means you can forget about operating the rear brake - it's done automatically for you.

Theory of Emergency Braking

Perhaps "theory" might be a strong word.

Basically somewhere between 10% and 30% of your bikes braking force comes from the rear brake, and the rest from the front brake.

Why does this number vary so much? It's all to do with the weight on the rear tyre. The more weight the greater the grip it has with the ground, and the more friction it can apply. If you have a pillion on board obviously more weight will be on the back tyre.
Cruisers tend to have a longer wheel base (and sometimes with saddle bags and the like), so they tend to have more weight on the rear tyre when compared to a sports bike, which are typically designed for a 50%/50% weight distribution.

But the weight on the rear tyre changes rapidly once you apply your front brake in an emergency. Consider the extreme case where you have the front brake applying the maximum force it can where your bike is up on the front wheel (a stoppie) balancing between the point of going over and falling back down. In this case 100% of the bikes weight has been transferred to the front tyre, and because the back wheel has zero weight on it the braking force it exerts is zero. Absolutely nothing.

The important bit to note here is that the braking force from the rear tyre becomes less as the weight transfers to the front tyre once braking has started. Also note that the amount of time the rear brake remains effective for will be dependent on your bike (sports versus cruiser for example). Even where you sit on your bike can effect it (do you sit in the middle of your seat, or with your bottom jammed against the back of the seat (like on a sports bike).

Also note that emergency braking technique is speed sensitive (mostly because speed affects the time for weight to transfer from the rear to front wheel - at higher speed the transfer occurs in less time), so the method used on a track from 200km/h is not likely to be as effective as performing an emergency stop from 100km/h or even 50km/h. At high speed the transfer can occur so quickly that it exceeds the time for human reflexes to react.

The last point to be aware of is that the likelihood of a tyre locking up under braking is reduced the more weight it has on it. A front wheel lock-up is considered the most serious, as it removes you ability to steer the bike.

Summary of Commonly Taught Methods

1. The Promocycle Foundation did a large study consisting of 820 emergency braking tests across a couple of different bikes (sports and a cruiser) to isolate out all the different factors.
   http://www.fmq.qc.ca/pdf/amorce-freinage_eng.pdf
   The Promocycle Foundation concluded that you should:
   
   • Close throttle and apply rear brake at the same time
   • Bring the bike vertical, brace arms, torso - basically stabilise and equalise bike
   • Apply front brake and de-clutch
   • Adjust front and rear brake pressure
   
   
2. In the United Kingdom the DSA control the guidelines, and they recommend:
   
   • Close the throttle
   • Engage the front brake, and then the rear brake
   • Progressively increase the pressure on both brakes
   • Pull in the clutch just before you stop, to afford maximum engine braking
   
   I emailed the DSA about the research that had gone into this technique. The DSA have not researched this, and the process is the result of consultations with experienced riders.
   
3. In the USA the American Motorcycle Safety Foundation teach:
   http://www.webbikeworld.com/Motorcyc...aking-tips.htm
   
   • Apply the rear brake hard and forget about it. Let it lock if it wants to.
   • Apply the front brake progressively harder and harder (they brake it into four stages)
   
   The AMSF approach is based more on research of psychology. Their research has indicated that our brains are not capable of managing both brakes at the same time. So that is why they say apply the rear brake with maximum force and forget about it. Then spend the remainder of your concentration on the front brake and bike control.
   
4. There is also a school of thought that you should use the front brake only (forget the rear brake). This seems to mostly originate from the personal experience of the rider involved. I can not locate any studies on this particular method. Track riders often promote this technique (the majority of track riders don't use the rear brake for braking effect).
   My personal impression is that the use of the front brake only will work better from high speed (aka 200km/h plus) since the rear brake has such a small amount of time that it can contribute anything to the net braking force of the bike.
   
5. There is a school of thought that you should be changing down while emergency braking. This is more related to another technique called brake and escape, as opposed to emergency braking (which I have stated the definition as being to bring the motorcycle to a complete halt in the shortest distance possible). Proponents of changing down for emergency braking suggest that engine braking can assist the emergency stopping procedure. My personal thoughts are that the front brake will provide more braking force than the engine can apply through changing down. If you risk leaving the engine engaged and changing down you run the far higher risk of having the engine drive against the brakes - increasing your braking distance. I have observed riders having trouble fully closing the throttle while performing an emergency braking session.

My personal thoughts are that newer riders should concentrate on emergency braking first, and then move onto learning about brake and escape.

So how do you do emergency braking?

I can't tell you an answer. I don't believe there is one technique that is effective for all riders for all bikes. I can tell you though that you need to select a method that you can execute without thinking. You must be able to do it second nature. When in an emergency your brain is likely to be overloaded. Fear can easily consume 90% of your cognitive thinking power.

However I suggest you consider the braking system for your bike (drum, disc, ABS or integrated), the amount of weight normally on the rear tyre (which is affected by your bike, luggage, pillion's, and where you sit), and then determine how effective your rear brake will be. It is also possible you may run into issues trying to co-ordinate the use the front and rear brake at the same time - and if so you need to take this into your emergency braking plan.
And then go practice the different techniques (front brake only, front first then rear, rear first then front, and playing with using the clutch straight away or delaying the clutch till the end).

You also need to consider the probability of locking the front wheel and how to deal with it. The techniques that engage the rear brake first tend to allow more front wheel brake pressure to be applied, because as soon as the rear brake is applied weight starts transferring onto the front wheel. And once again, the more weight on a wheel the less likely it is to lock.

I can tell you that people who I have helped with emergency braking never end up all using one single technique. And I hope this blog entry helps to explain why a "one size" does not fit all.