Discussion
...Or how to brake good.
Braking is another one of those actions we take completely for granted. Press the middle pedal (or the left pedal depending on your choice of transmission) and the car will slow down and eventually stop. Press it harder and the car will stop more quickly. There can't be any more to it than that, can there?
Come on - you should know me better than that by now.
If there is one skill which immediately seperates the good from the bad, the smooth from the rough and the delicately dainty ballet-footed from the clumpy clog-footed lead-diving-boot types, it's braking. Jump in with a rough driver and their poor braking skills will be the first thing you notice. Sit alongside a smooth driver and you'll never notice their braking at all. For passengers who have no experience of advanced driving and even those with no interest in driving, smooth braking is something they will appreciate more than any other skill - especially if they are used to sitting next to a poor braker.
So where do we start? Have a read of "Acceleraton Nonsense" to start with...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Good braking is a skill which should always be combined with good acceleration sense, so an understanding of the principles of correct accelerator use is important. If you're well practiced and your timing and planning are good, its surprising how little you actually need to use the brakes, even in traffic. This may sound like an obvious statement, but not using the brakes is always smoother than using the brakes.
The Brakes
So where do we start with actually braking? Lets have a look at whats happening mechanically when you press the brake pedal. Like all mechanical systems, brakes have developed considerably since the early years of motoring, but the principles have remained the same for many years.
The service brake, or foot brake, is connected to the brakes on all four wheels through a dual-circuit hydraulic system. Press the brake pedal, and with the mechanical assistance of a servo or vacuum pump, pressure is built up in the hydraulic fluid, through the brake lines, to the brakes themselves.
Once the hydraulic pressure reaches the brakes, it is used to force a pair of brake pads inwards against a rotating brake disk, or to force the brake shoes outwards against a rotating brake drum. The friction between the pads and disk, or the shoes and drum, cause the wheel to slow.
The next bit is really important, and is often forgotten when thinking about braking. The slowing wheel then slows the car due to friction between the tyre and the road surface. So the tyre, and the road surface itself, form an integral part of a cars braking mechanism. If you think about it, the tyre and the road surface are by far the most variable and inconsistent components in the whole system. Disks, pads, shoes and drums are all subject to wear, of course, but their function usually only deteriorates over time, and rarely deteriorates suddenly without warning. Road surfaces, on the other hand, are almost universally inconsistant. They vary from street to street, road to road, and often from lamp-post to lamp-post.
So although you may be extremely diligent when it comes to maintaining your brakes, tyres and tyre pressures, the one aspect of your braking system which you have no control over - and which you therefore have to use your observation and planning skills to negotiate - is the road surface.
An inevitable consequence of braking is weight transfer and how it affects the balance of the car under braking. I explored balance in a previous post, with a small section on braking here...
www.pistonheads.com/gassing/topic.asp?h=0&t=36...
One way in which vehicle manufacturers compensate for the forward weight transfer under braking is by generally fitting larger, more powerful brakes on the front of the vehicle than the rear. The braking system will be designed to apply more braking to the front wheels and less to the rear wheels to keep the car balanced under hard braking. Most cars used to be fitted with disk brakes on the front axle and drums on the rear, but this is becoming less common these days.
This is one reason why brakes are considered to be less effective when travelling in reverse - the weight transfer makes the less effective brakes at the rear do most of the work and the stronger brakes at the front are less effective.
The other reason brakes are traditionally considered to be less effective in reverse is due to the design of twin leading shoe drum brakes, but this will be a long enough post without going into detail about drum brake designs.
Brake Testing
We'll look at braking in detail shortly, but it's always good to know that your brakes are actually working. Isn't it?
We all, consciously or unconsciously, have our own little "starting drill" when we first get into the car. It might just be start-up and seatbelt on, or it might be a full advanced starting drill, or an old fashioned CID starting drill (we're in, we're off).
Whatever you prefer is fine by me, but it's good practice to include a quick "static brake test". Nothing complicated - just give the brake pedal a quick shove before you start the car. There should be plenty of resistance in the pedal - particularly with the engine off, due to the lack of servo assistance. If there isn't, and the pedal is soft, or "long", there is likely to be a serious fault with the brakes and probably a puddle of brake fluid under the car, so you'd be best advised not to continue with your journey.
I should add at this point, that in 28 years of driving, I have never once had a major brake failure, but for the sake of shoving your foot on the brake pedal for a second while you're putting your seatbelt on, the small amount of effort has got to be worthwhile, hasn't it? Try it for a couple of weeks and you'll soon be doing it without thinking.
Many police driving schools also advocate a "moving brake test". Just after setting off from stationary, students are required to accelerate up to around 20mph, before giving the brakes a short press and braking down to about 10mph. This allows them to check the brakes are operating correctly and evenly without pulling to either side.
A moving brake test is good practice, of course, but it's also a bit of a faff at times, and there is no reason you can't just incorporate a brief brake test into your ordinary driving, without it being obvious. Setting off from home? Just brake a little earlier than normal for the first hazard. Car park? Brake slightly earlier for the first corner or exit. Either way, make a quick mental note that the brakes are working fine, and if they're not, you're only travelling at a low speed and a combination of gears and handbrake should bring you to a halt. Even if this doesn't work, the low speed should allow you to find a suitable object to nudge into without causing too much damage.
Operating The Brakes
As with most of a car's major controls (apart from, of course, the switches), the brake pedal is not a switch. By which I mean, the brakes are never simply "on" or "off", but instead, they are almost infinitely variable in their effectiveness, depending on how softly or firmly you press the pedal.
For this section, we'll consider that the application of the brakes is part of a well planned approach to a hazard, rather than an emergency braking situation ( which we'll look at a bit later).
Three Phase Braking
Many advanced drivers and instructors make reference to "three phases of braking", by which they mean that the brakes are first applied smoothly and gently in the first phase, then more firmly and assertively in the second phase, and then tapering off smoothly in the third phase until the brakes are completely released or the car comes to a stop.
Although "three phase braking" is a simple enough concept, particularly when teaching a relatively inexperienced driver, I'm not so sure that it is an accurate description of the actions required to smoothly reduce the speed of a vehicle. Each of those three phases could easily be split into many more phases, from the very first initial touch of the pedal, through the first small application of pressure, right through to the delicate smooth release and then re-application once the car is stationary.
In other words, in my view, there is either one phase - braking, or there are an infinite number of phases from start to finish.
To avoid getting too complicated, and to keep this post relevent to the proponents of the three phase principle, I'll split braking into the three phases, but explain them all in detail. Just bear in mind, though, that each phase should blend seamlessly into the next, so it's not simply three seperate braking actions, but one single action which contains seperate elements throughought.
I hope this makes sense so far!
First Application
Your right foot is almost always occupied when you're driving. Its either on the accelerator or on the brake and it's by far the most sensitive. There are many advocates of left foot braking, and although I fully appreciate the benefits in competitive driving, I'm a strong believer that left foot braking is for the track or forest stage only and not for the road, even in cars with two pedal transmissions.
The nature of the brake pedal is that, unlike the accelerator and clutch, it has a resistance in its operation which requires a reasonably firm pressure from your right foot. For this reason, it's important that the ball of your foot is squarely on the pedal, rather than brushing the right hand edge of the pedal.
Think about it - if your foot slips off the accelerator, it is highly unlikely that you'll be put in danger (unless you're in the middle of a very tight overtake - which you shouldn't be!). If your foot slips off the brake, however, things can go very wrong, very quickly. So, roll on and off the accelerator by all means, but make sure you're squarely over the brake pedal when you're using it.
First application should be a very light touch - this will start to build up hydraulic pressure in the system and push the brake pads up to the face of the disk. Effectively, you're "taking up the slack" in the system, although the "slack" is actually tiny. Think of the first touch as priming the brakes ready for use.
Then start to apply the brakes very gently. Bear in mind that the first actual pressure that you apply to the pedal will switch on your brake lights, letting following drivers know you're braking and slowing.
Increasing The Pressure
Moving on to what is commonly referred to as the second phase, start to gradually and smoothly increase the pressure on the brake pedal.
How much by?
How long is a piece of string?
The correct answer is "by however much is appropriate in the circumstances". How much speed do you need to lose? How much distance have you got? How effective are your brakes? What is the road surface like?
The middle phase may only involve a very light squeeze of the brake pedal to lose a few miles per hour. At the other end of the spectrum, it is possible to brake extremely hard in the middle phase if you're pressing on or if information changes, whilst still keeping the braking action smooth and controlled.
So how much is entirely up to you, but keep your inputs "tapered" rather than sudden and sharp and you'll be braking effectively and competently.
Coming Ooooooooooooff The Brakes
As you come towards the end of your braking action, the speed of your car will be getting down close to the speed you require and you'll start to reduce the pressure you're applying to the brake pedal.
This is where many people - even very competent and qualified advanced drivers - can regularly get it wrong.
I'll split this section into two parts - braking to slow and braking to a stop.
When braking to slow - lets use braking to slow for a corner as an example - a driver will assess the corner on approach, concentrate on braking down to the appropriate speed, but then jump immediately off the brakes to get the appropriate gear for the corner. It's this "jumping off" the brakes which is the most common fault. The idea, on entering the corner, is to smoothly balance the car under a little acceleration which will increase as the corner opens up. By jumping straight off the brakes, you're unsettling the car and moving the weight and balance around in a rough manner. If you take just half a second longer to come off the brakes, the weight transfer is managed in a much smoother manner and the car will be better balanced when you move to the accelerator and start to steer.
Those instructors and observers amongst you may want to try my little instructional technique, which usually cures people of this habit. Just before the driver's speed is correct, tell them to come ooooooooff the brakes. Works a treat!
When braking to a stop, many people have a habit of keeping a little too much pressure on the brake pedal just as the car actually comes to a full stop. Keeping too much pressure on makes the brakes "grab" at the point the car stops, and results in driver and passengers nodding forward in their seat, and then back into their head restraints.
This is a very common fault, and part of the problem is that drivers notice it less than passengers, so most ordinary drivers never pick the fault up or learn how to correct it.
The solution is very simple - just before the car comes to a stop, reduce the pressure on the brake pedal and reduce the rate of retardation for the last couple of feet. Once the car is down to 1 or 2mph, it will need only the slightest touch on the brake pedal to actually bring the car to a stop and it should be possible to come to a stop with almost no physical reaction by the cars occupants.
One key aspect with this technique is that as soon as the car has actually stopped, you should then increase the pressure on the pedal until you have applied the handbrake or moved off. This is because the very light pressure required to roll the car to a stop is often not enough pressure to hold the car once its stationary. So the very light touch down to a stop should be followed by a quick increase in pressure to hold the car stationary.
Trust me on this - you can brake as hard as you like when you're stationary and it'll be silky smooth!
Braking Distances
You've all read the braking distances in the Highway Code and no doubt you've all memorised them for a test at some point or points in your life. But how realistic are they? Does it really take 45 feet to stop from 30mph? Or 245 feet to stop from 70mph?
The truth is that even an average driver in a modern, well maintained car can easily beat those distances, even on a wet road.
Think of the HC braking distances as a worst-case scenario. A dopy driver in a poorly maintained car with bald tyres and a slippery wet road surface will probably need the full 45 feet plus thinking distance to come to a stop. They may not be wholly relevent to you in 2014, but they may be relevent to the dopy driver in a poorly maintained car who is following you too close in the rain - something to bear in mind when setting your own following position. The more distance you give yourself to brake, the less chance there is of the car behind running into you.
Managing Heat
Slowing a ton and a half of metal down from high speeds through 6 square inches of brake pad rubbing against an iron or ceramic disk spinning at high revs imevitably generates an enourmous amount of heat. If you're out on a spirited drive or a trackday and you're using the brakes hard and often, this heat can start to cause issues, so how do you recognise these issues? And how do you deal with them?
The first issue is glazing of the pads. Although brake pad material is extremely robust and designed to work at high temperatures, the particles on the surface of the brake pad can momentarily melt under constant heavy use, and then resolidify as a glassy "glaze" which has much less friction and makes your brakes much less effective. At the same time, this melting can cause a release of gas from the pad material which can further reduce tye effectiveness of the brakes.
Manufacturers have come up with a number of solutions to pad glazing and gas release, particularly on high-performance cars. "Slotted" brake disks are designed so that the edges of the slots constantly de-glaze the surface of the pads. Drilled or dimpled brake disks allow the gasses to disperse without causing a drop in braking performance.
How do you recognise glazing? You'll find that your brakes will require more and more effort in order to reach the same braking effect. I've also found that you can feel the smoothness of the pads against the disk through your foot on the pedal - you can feel that there is less friction in the system.
The solution, as with many aspects of driving, is to remove the cause. In this case, the cause is excessive heat build-up through hard braking, so if you're on the road, slow it down, try to use the brakes less, but keep driving for a few miles so that the air continues flowing over the brakes and cools them down. The temperature will drop quite quickly, after which you should de-glaze the pads by braking firmly in short busts about half-a-dozen times.
If you're on a trackday, pull off the track and let the brakes cool off. It'll take a bit longer if the car is stationary and you should leave the car in gear with the handbrake OFF, as a hot handbrake can stick itself to the disk as it cools.
The other potential issue is vapour-lock. Brake fluid is hygroscopic, which means that, over time, it can absorb tiny amounts of water from the atmosphere. If you've been braking particularly hard and your brake fluid is knocking on a bit, there is a danger that the absorbed water will boil and become a gas. Unlike brake fluid, gas is easily compressed, so the first you'll know is that the brake pedal will go to the floor.
The key to avoiding vapour lock is to make sure you change yoir brake fluid every three years or so.
Emergency Braking
If you're a good driver with sound observation skills and good planning, you should rarely - if ever - need to apply emergency braking. None of us are so conceited, however, to think that we'll never need it, so lets look at an emergency situation where, despite your best efforts, you need to stop urgently in as short a distance as possible.
Most modern cars are fitted with anti-lock braking systems. Much has been written about these systems and there is a big clue to their function in the name. Under very heavy braking, ABS recognises when a wheel is starting to lock up, and then momentarily releases that brake before re-applying it to the point of lock-up, releasing it again, rinse, and repeat.
But why do we not want our wheels to lock up? Surely if you've applied all the brakes to the wheels to the point where the wheel locks and then skids along the road surface, you'll stop in the shortest distance, won't you?
Interestingly, no, you won't. Apart from on loose gravel or deep snow, in which case you might, but this post is getting long enough without me drifting off onto obscure details.
So on normal tarmac, the truth is that a cars brakes are most effective at the point just before the wheels lock up. A very skilled driver can hold a car just at this point and stop the car effectivley without locking up. It's called "threshold braking" and requires much practice, usually on a track or runway before you become competent.
A rotating wheel will stop more quickly, and in less distance than a locked wheel. The other benefit of keeping the wheels turning is that there is still a little tyre grip left with which to steer the car. A car with locked wheels will simply continue in a straight line until it stops. A car with rotating wheels can still be steered around a hazard.
ABS effectively allows untrained drivers to apply threshold braking in an emergency situation.
The trouble is, that most people, even in an emergency, don't brake hard enough. Some manufacturers have recognised this and introduced "brake assist" systems which recognise the speed at which a driver has applied the brakes, and then add some extra brake effort to ensure the brakes are fully applied.
My advice in an emergency, if you're driving a car with ABS is simple.
Muller the brakes as hard as you possibly can, and steer around the hazard if possible.
I can't really make it any more simple, can I? Forget three phase braking and heat build-up and threshold braking and everything else. Its's an emergency and all the niceties of smoothness and balance go out of the window. Stamp on that brake pedal as quickly and as hard as you possibly can and keep it pressed hard - try to push it out through the floor of the car until you come to a stop.
The car will work it's ABS magic - you may feel a vibration through the pedal, which is the car releasing and reapplying the brakes in quick succession - and will stop as quickly as possible whilst allowing you to retain some steering control if you need it.
But what about the traditionalists with TVRs and Caterhams and old Porsches without ABS?
My advice - at least initially - is the same. In an emergency, muller those brakes as hard as you possibly can.
The difference comes if your wheels lock up. If you realise that you've locked up,and you're travelling in a straight line with no steering, you must do something which is quite difficult in the circumstances.
Come off the brakes.
It's the last thing you want to do, but coming off the brakes for a fraction of a second will allow the wheels to rotate and give you some steering back. Then reapply the brakes till they lock, release, rinse and repeat.
It's called "cadence braking" and replicates - albeit at a much slower rate - the effects of ABS.
Cadence braking saved my life once. I was driving down a steep hill on a rural road in mid-winter at night. The road bent round to the right with a very long drop off a cliff to the left. I started to brake and... Nothing. The road was sheet ice and I was going over the edge - no question.
I pumped that brake pedal like I was trying to stamp a tarantula to death and steered right. It was quite odd, because my speed was already quite slow, but there was virtually no road grip, so unlike most accidents, I had time to take in what was happening.
I managed to get the car's speed right down and negotiate the bend without leaving the road. If I'd left the brakes fully on, without a doubt I'd have been over the cliff. So trust me - through personal experience, although it's an old fashioned technique, cadence braking does genuinely work. As long as you can keep your head and get off the brakes when every fibre of your body wants to keep the brake pedal mashed.
So that's it for braking. Sorry for rambling on, but as you can see, there is more to it than most people think.
Braking is another one of those actions we take completely for granted. Press the middle pedal (or the left pedal depending on your choice of transmission) and the car will slow down and eventually stop. Press it harder and the car will stop more quickly. There can't be any more to it than that, can there?
Come on - you should know me better than that by now.
If there is one skill which immediately seperates the good from the bad, the smooth from the rough and the delicately dainty ballet-footed from the clumpy clog-footed lead-diving-boot types, it's braking. Jump in with a rough driver and their poor braking skills will be the first thing you notice. Sit alongside a smooth driver and you'll never notice their braking at all. For passengers who have no experience of advanced driving and even those with no interest in driving, smooth braking is something they will appreciate more than any other skill - especially if they are used to sitting next to a poor braker.
So where do we start? Have a read of "Acceleraton Nonsense" to start with...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Good braking is a skill which should always be combined with good acceleration sense, so an understanding of the principles of correct accelerator use is important. If you're well practiced and your timing and planning are good, its surprising how little you actually need to use the brakes, even in traffic. This may sound like an obvious statement, but not using the brakes is always smoother than using the brakes.
The Brakes
So where do we start with actually braking? Lets have a look at whats happening mechanically when you press the brake pedal. Like all mechanical systems, brakes have developed considerably since the early years of motoring, but the principles have remained the same for many years.
The service brake, or foot brake, is connected to the brakes on all four wheels through a dual-circuit hydraulic system. Press the brake pedal, and with the mechanical assistance of a servo or vacuum pump, pressure is built up in the hydraulic fluid, through the brake lines, to the brakes themselves.
Once the hydraulic pressure reaches the brakes, it is used to force a pair of brake pads inwards against a rotating brake disk, or to force the brake shoes outwards against a rotating brake drum. The friction between the pads and disk, or the shoes and drum, cause the wheel to slow.
The next bit is really important, and is often forgotten when thinking about braking. The slowing wheel then slows the car due to friction between the tyre and the road surface. So the tyre, and the road surface itself, form an integral part of a cars braking mechanism. If you think about it, the tyre and the road surface are by far the most variable and inconsistent components in the whole system. Disks, pads, shoes and drums are all subject to wear, of course, but their function usually only deteriorates over time, and rarely deteriorates suddenly without warning. Road surfaces, on the other hand, are almost universally inconsistant. They vary from street to street, road to road, and often from lamp-post to lamp-post.
So although you may be extremely diligent when it comes to maintaining your brakes, tyres and tyre pressures, the one aspect of your braking system which you have no control over - and which you therefore have to use your observation and planning skills to negotiate - is the road surface.
An inevitable consequence of braking is weight transfer and how it affects the balance of the car under braking. I explored balance in a previous post, with a small section on braking here...
www.pistonheads.com/gassing/topic.asp?h=0&t=36...
One way in which vehicle manufacturers compensate for the forward weight transfer under braking is by generally fitting larger, more powerful brakes on the front of the vehicle than the rear. The braking system will be designed to apply more braking to the front wheels and less to the rear wheels to keep the car balanced under hard braking. Most cars used to be fitted with disk brakes on the front axle and drums on the rear, but this is becoming less common these days.
This is one reason why brakes are considered to be less effective when travelling in reverse - the weight transfer makes the less effective brakes at the rear do most of the work and the stronger brakes at the front are less effective.
The other reason brakes are traditionally considered to be less effective in reverse is due to the design of twin leading shoe drum brakes, but this will be a long enough post without going into detail about drum brake designs.
Brake Testing
We'll look at braking in detail shortly, but it's always good to know that your brakes are actually working. Isn't it?
We all, consciously or unconsciously, have our own little "starting drill" when we first get into the car. It might just be start-up and seatbelt on, or it might be a full advanced starting drill, or an old fashioned CID starting drill (we're in, we're off).
Whatever you prefer is fine by me, but it's good practice to include a quick "static brake test". Nothing complicated - just give the brake pedal a quick shove before you start the car. There should be plenty of resistance in the pedal - particularly with the engine off, due to the lack of servo assistance. If there isn't, and the pedal is soft, or "long", there is likely to be a serious fault with the brakes and probably a puddle of brake fluid under the car, so you'd be best advised not to continue with your journey.
I should add at this point, that in 28 years of driving, I have never once had a major brake failure, but for the sake of shoving your foot on the brake pedal for a second while you're putting your seatbelt on, the small amount of effort has got to be worthwhile, hasn't it? Try it for a couple of weeks and you'll soon be doing it without thinking.
Many police driving schools also advocate a "moving brake test". Just after setting off from stationary, students are required to accelerate up to around 20mph, before giving the brakes a short press and braking down to about 10mph. This allows them to check the brakes are operating correctly and evenly without pulling to either side.
A moving brake test is good practice, of course, but it's also a bit of a faff at times, and there is no reason you can't just incorporate a brief brake test into your ordinary driving, without it being obvious. Setting off from home? Just brake a little earlier than normal for the first hazard. Car park? Brake slightly earlier for the first corner or exit. Either way, make a quick mental note that the brakes are working fine, and if they're not, you're only travelling at a low speed and a combination of gears and handbrake should bring you to a halt. Even if this doesn't work, the low speed should allow you to find a suitable object to nudge into without causing too much damage.
Operating The Brakes
As with most of a car's major controls (apart from, of course, the switches), the brake pedal is not a switch. By which I mean, the brakes are never simply "on" or "off", but instead, they are almost infinitely variable in their effectiveness, depending on how softly or firmly you press the pedal.
For this section, we'll consider that the application of the brakes is part of a well planned approach to a hazard, rather than an emergency braking situation ( which we'll look at a bit later).
Three Phase Braking
Many advanced drivers and instructors make reference to "three phases of braking", by which they mean that the brakes are first applied smoothly and gently in the first phase, then more firmly and assertively in the second phase, and then tapering off smoothly in the third phase until the brakes are completely released or the car comes to a stop.
Although "three phase braking" is a simple enough concept, particularly when teaching a relatively inexperienced driver, I'm not so sure that it is an accurate description of the actions required to smoothly reduce the speed of a vehicle. Each of those three phases could easily be split into many more phases, from the very first initial touch of the pedal, through the first small application of pressure, right through to the delicate smooth release and then re-application once the car is stationary.
In other words, in my view, there is either one phase - braking, or there are an infinite number of phases from start to finish.
To avoid getting too complicated, and to keep this post relevent to the proponents of the three phase principle, I'll split braking into the three phases, but explain them all in detail. Just bear in mind, though, that each phase should blend seamlessly into the next, so it's not simply three seperate braking actions, but one single action which contains seperate elements throughought.
I hope this makes sense so far!
First Application
Your right foot is almost always occupied when you're driving. Its either on the accelerator or on the brake and it's by far the most sensitive. There are many advocates of left foot braking, and although I fully appreciate the benefits in competitive driving, I'm a strong believer that left foot braking is for the track or forest stage only and not for the road, even in cars with two pedal transmissions.
The nature of the brake pedal is that, unlike the accelerator and clutch, it has a resistance in its operation which requires a reasonably firm pressure from your right foot. For this reason, it's important that the ball of your foot is squarely on the pedal, rather than brushing the right hand edge of the pedal.
Think about it - if your foot slips off the accelerator, it is highly unlikely that you'll be put in danger (unless you're in the middle of a very tight overtake - which you shouldn't be!). If your foot slips off the brake, however, things can go very wrong, very quickly. So, roll on and off the accelerator by all means, but make sure you're squarely over the brake pedal when you're using it.
First application should be a very light touch - this will start to build up hydraulic pressure in the system and push the brake pads up to the face of the disk. Effectively, you're "taking up the slack" in the system, although the "slack" is actually tiny. Think of the first touch as priming the brakes ready for use.
Then start to apply the brakes very gently. Bear in mind that the first actual pressure that you apply to the pedal will switch on your brake lights, letting following drivers know you're braking and slowing.
Increasing The Pressure
Moving on to what is commonly referred to as the second phase, start to gradually and smoothly increase the pressure on the brake pedal.
How much by?
How long is a piece of string?
The correct answer is "by however much is appropriate in the circumstances". How much speed do you need to lose? How much distance have you got? How effective are your brakes? What is the road surface like?
The middle phase may only involve a very light squeeze of the brake pedal to lose a few miles per hour. At the other end of the spectrum, it is possible to brake extremely hard in the middle phase if you're pressing on or if information changes, whilst still keeping the braking action smooth and controlled.
So how much is entirely up to you, but keep your inputs "tapered" rather than sudden and sharp and you'll be braking effectively and competently.
Coming Ooooooooooooff The Brakes
As you come towards the end of your braking action, the speed of your car will be getting down close to the speed you require and you'll start to reduce the pressure you're applying to the brake pedal.
This is where many people - even very competent and qualified advanced drivers - can regularly get it wrong.
I'll split this section into two parts - braking to slow and braking to a stop.
When braking to slow - lets use braking to slow for a corner as an example - a driver will assess the corner on approach, concentrate on braking down to the appropriate speed, but then jump immediately off the brakes to get the appropriate gear for the corner. It's this "jumping off" the brakes which is the most common fault. The idea, on entering the corner, is to smoothly balance the car under a little acceleration which will increase as the corner opens up. By jumping straight off the brakes, you're unsettling the car and moving the weight and balance around in a rough manner. If you take just half a second longer to come off the brakes, the weight transfer is managed in a much smoother manner and the car will be better balanced when you move to the accelerator and start to steer.
Those instructors and observers amongst you may want to try my little instructional technique, which usually cures people of this habit. Just before the driver's speed is correct, tell them to come ooooooooff the brakes. Works a treat!
When braking to a stop, many people have a habit of keeping a little too much pressure on the brake pedal just as the car actually comes to a full stop. Keeping too much pressure on makes the brakes "grab" at the point the car stops, and results in driver and passengers nodding forward in their seat, and then back into their head restraints.
This is a very common fault, and part of the problem is that drivers notice it less than passengers, so most ordinary drivers never pick the fault up or learn how to correct it.
The solution is very simple - just before the car comes to a stop, reduce the pressure on the brake pedal and reduce the rate of retardation for the last couple of feet. Once the car is down to 1 or 2mph, it will need only the slightest touch on the brake pedal to actually bring the car to a stop and it should be possible to come to a stop with almost no physical reaction by the cars occupants.
One key aspect with this technique is that as soon as the car has actually stopped, you should then increase the pressure on the pedal until you have applied the handbrake or moved off. This is because the very light pressure required to roll the car to a stop is often not enough pressure to hold the car once its stationary. So the very light touch down to a stop should be followed by a quick increase in pressure to hold the car stationary.
Trust me on this - you can brake as hard as you like when you're stationary and it'll be silky smooth!
Braking Distances
You've all read the braking distances in the Highway Code and no doubt you've all memorised them for a test at some point or points in your life. But how realistic are they? Does it really take 45 feet to stop from 30mph? Or 245 feet to stop from 70mph?
The truth is that even an average driver in a modern, well maintained car can easily beat those distances, even on a wet road.
Think of the HC braking distances as a worst-case scenario. A dopy driver in a poorly maintained car with bald tyres and a slippery wet road surface will probably need the full 45 feet plus thinking distance to come to a stop. They may not be wholly relevent to you in 2014, but they may be relevent to the dopy driver in a poorly maintained car who is following you too close in the rain - something to bear in mind when setting your own following position. The more distance you give yourself to brake, the less chance there is of the car behind running into you.
Managing Heat
Slowing a ton and a half of metal down from high speeds through 6 square inches of brake pad rubbing against an iron or ceramic disk spinning at high revs imevitably generates an enourmous amount of heat. If you're out on a spirited drive or a trackday and you're using the brakes hard and often, this heat can start to cause issues, so how do you recognise these issues? And how do you deal with them?
The first issue is glazing of the pads. Although brake pad material is extremely robust and designed to work at high temperatures, the particles on the surface of the brake pad can momentarily melt under constant heavy use, and then resolidify as a glassy "glaze" which has much less friction and makes your brakes much less effective. At the same time, this melting can cause a release of gas from the pad material which can further reduce tye effectiveness of the brakes.
Manufacturers have come up with a number of solutions to pad glazing and gas release, particularly on high-performance cars. "Slotted" brake disks are designed so that the edges of the slots constantly de-glaze the surface of the pads. Drilled or dimpled brake disks allow the gasses to disperse without causing a drop in braking performance.
How do you recognise glazing? You'll find that your brakes will require more and more effort in order to reach the same braking effect. I've also found that you can feel the smoothness of the pads against the disk through your foot on the pedal - you can feel that there is less friction in the system.
The solution, as with many aspects of driving, is to remove the cause. In this case, the cause is excessive heat build-up through hard braking, so if you're on the road, slow it down, try to use the brakes less, but keep driving for a few miles so that the air continues flowing over the brakes and cools them down. The temperature will drop quite quickly, after which you should de-glaze the pads by braking firmly in short busts about half-a-dozen times.
If you're on a trackday, pull off the track and let the brakes cool off. It'll take a bit longer if the car is stationary and you should leave the car in gear with the handbrake OFF, as a hot handbrake can stick itself to the disk as it cools.
The other potential issue is vapour-lock. Brake fluid is hygroscopic, which means that, over time, it can absorb tiny amounts of water from the atmosphere. If you've been braking particularly hard and your brake fluid is knocking on a bit, there is a danger that the absorbed water will boil and become a gas. Unlike brake fluid, gas is easily compressed, so the first you'll know is that the brake pedal will go to the floor.
The key to avoiding vapour lock is to make sure you change yoir brake fluid every three years or so.
Emergency Braking
If you're a good driver with sound observation skills and good planning, you should rarely - if ever - need to apply emergency braking. None of us are so conceited, however, to think that we'll never need it, so lets look at an emergency situation where, despite your best efforts, you need to stop urgently in as short a distance as possible.
Most modern cars are fitted with anti-lock braking systems. Much has been written about these systems and there is a big clue to their function in the name. Under very heavy braking, ABS recognises when a wheel is starting to lock up, and then momentarily releases that brake before re-applying it to the point of lock-up, releasing it again, rinse, and repeat.
But why do we not want our wheels to lock up? Surely if you've applied all the brakes to the wheels to the point where the wheel locks and then skids along the road surface, you'll stop in the shortest distance, won't you?
Interestingly, no, you won't. Apart from on loose gravel or deep snow, in which case you might, but this post is getting long enough without me drifting off onto obscure details.
So on normal tarmac, the truth is that a cars brakes are most effective at the point just before the wheels lock up. A very skilled driver can hold a car just at this point and stop the car effectivley without locking up. It's called "threshold braking" and requires much practice, usually on a track or runway before you become competent.
A rotating wheel will stop more quickly, and in less distance than a locked wheel. The other benefit of keeping the wheels turning is that there is still a little tyre grip left with which to steer the car. A car with locked wheels will simply continue in a straight line until it stops. A car with rotating wheels can still be steered around a hazard.
ABS effectively allows untrained drivers to apply threshold braking in an emergency situation.
The trouble is, that most people, even in an emergency, don't brake hard enough. Some manufacturers have recognised this and introduced "brake assist" systems which recognise the speed at which a driver has applied the brakes, and then add some extra brake effort to ensure the brakes are fully applied.
My advice in an emergency, if you're driving a car with ABS is simple.
Muller the brakes as hard as you possibly can, and steer around the hazard if possible.
I can't really make it any more simple, can I? Forget three phase braking and heat build-up and threshold braking and everything else. Its's an emergency and all the niceties of smoothness and balance go out of the window. Stamp on that brake pedal as quickly and as hard as you possibly can and keep it pressed hard - try to push it out through the floor of the car until you come to a stop.
The car will work it's ABS magic - you may feel a vibration through the pedal, which is the car releasing and reapplying the brakes in quick succession - and will stop as quickly as possible whilst allowing you to retain some steering control if you need it.
But what about the traditionalists with TVRs and Caterhams and old Porsches without ABS?
My advice - at least initially - is the same. In an emergency, muller those brakes as hard as you possibly can.
The difference comes if your wheels lock up. If you realise that you've locked up,and you're travelling in a straight line with no steering, you must do something which is quite difficult in the circumstances.
Come off the brakes.
It's the last thing you want to do, but coming off the brakes for a fraction of a second will allow the wheels to rotate and give you some steering back. Then reapply the brakes till they lock, release, rinse and repeat.
It's called "cadence braking" and replicates - albeit at a much slower rate - the effects of ABS.
Cadence braking saved my life once. I was driving down a steep hill on a rural road in mid-winter at night. The road bent round to the right with a very long drop off a cliff to the left. I started to brake and... Nothing. The road was sheet ice and I was going over the edge - no question.
I pumped that brake pedal like I was trying to stamp a tarantula to death and steered right. It was quite odd, because my speed was already quite slow, but there was virtually no road grip, so unlike most accidents, I had time to take in what was happening.
I managed to get the car's speed right down and negotiate the bend without leaving the road. If I'd left the brakes fully on, without a doubt I'd have been over the cliff. So trust me - through personal experience, although it's an old fashioned technique, cadence braking does genuinely work. As long as you can keep your head and get off the brakes when every fibre of your body wants to keep the brake pedal mashed.
So that's it for braking. Sorry for rambling on, but as you can see, there is more to it than most people think.
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