One of the inputs that we give to a car through use of the driving controls that can cause a major change in vehicle-balance is the application of the brakes.
When you apply your brakes, the weight will shift towards the front of the car making that end heavier and the rear end lighter. That is why manufacturers fit the more powerful brakes to the front wheel assemblies, simply because they do the most work in helping you to stop. They also fit what is called a pressure limiting valve in the lines to the rear brakes that senses this change in balance and adjusts the amount of fluid pressure that reaches the rear wheels accordingly in an effort to prevent those now much lighter wheels from locking up into a skid.
Braking is perhaps something that nearly every motorist takes for granted. You are driving along the road and you come across a situation that requires you to lose speed. Without further ado you put your foot on the pedal and you slow down, but the question is how do you brake, by what degree and when? What is it that actually stops the car?
There will be many people that have travelled as a passenger in car driven by a friend, spouse or relative and wished they had remembered to travel with their surgical collars. You know the type of driver? The one that just pokes at the brake pedal separating your vertebrae every time they slow the car down or leaves it very late so that what should have been a gentle slowing now becomes an eye popping and rather hurried stop. Apart from being very uncomfortable, and there being an enhanced risk of skidding or control loss, it is quite harmful for the car. Think about the stress it places upon the suspension linkages, the brake components and the engine mountings. Yes, the engine mountings - and the gearbox too.
For the highest degree of control, braking should be completed when travelling in a straight line and always be carried out progressively. That is to say, that upon realising the need to stop you firstly rest your foot on the pedal and then gradually increase the pressure until the desired amount of braking effect is achieved at the wheels. Once your speed has been reduced sufficiently the procedure is completed in reverse, i.e. you release the pressure on the pedal in the same progressive manner. It also should be commenced early to give time for it to be delivered smoothly and progressively, so as to provide the maximum degree of vehicle control.
Braking whilst cornering will immediately put the car off-balance as under the effect of deceleration the vehicle weight is pitched forward, and because you are steering, into one front corner. This places one hell of a lot of load onto that one suspension unit and creates a great deal of extra work for one tyre to cope with. When this happens, particularly with front wheel drive vehicles, the rear of the car becomes lighter, especially the diagonally opposite wheel and suspension unit. This makes it more difficult for the back tyres to grip the road so that the back of the car can more easily be provoked into overtaking the front because all the slowing is being induced by the front end. The other product of braking into a bend is that the car will push straight on instead of changing direction as you had intended.
The usual way in which the general motoring public deal with bends and corners, and I follow them every single day, is that they will decelerate, brake and change down through the gearbox all whilst steering around a bend, and usually all at the same time. In fact most will only reach the desired road-speed, and have selected the appropriate gear, by the time they are at the halfway-round point. The effect of this is very uncomfortable for the car because as soon as the foot is lifted, and/or the brakes are applied, the balance of the car shifts forward, as we have already said, and has produced what is definitely a spin-inducing situation. It knocks the hell out of your tyres as well. Drivers that brake into corners will scrub the outer shoulders of their front tyres away and won’t get anywhere near the mileage they could out of them.
The method we advocate in relation to braking for corners is to firstly bring down the speed of the car until we are happy that it is appropriate for corner or bend we are about to negotiate, whilst still travelling in a straight line. Having settled the car to the speed required we now directly select the most suitable gear that will give us the necessary response for the speed at which we are travelling - again before we start to turn into the corner. By the time we do turn into the corner we are travelling at the right speed and with the right gear engaged
(I won't go into the positioning here as that would over-complicate matters). When we actually take the car around a corner/bend we are doing so under enough power to keep the engine pulling, but without accelerating so achieving the best-balance situation in terms of vehicle stability.
