- The brakes that come with a factory road car do great when on the road.
When you take your car to the track, brake cooling is something that always
needs to be considered, it's really rare to have a factory braking system that can
deal with the temperatures generated on track.
The primary consideration when looking at brake cooling is for safety and reliability
of the braking system.
Although the performance of the brakes is also closely linked to the operating temperature
of both the disc and the pads.
In a motorsport application, the primary method for cooling the brakes is by using
external cold air sourced from outside the car and directing it towards the discs.
Here we've got a well used motorsport disc.
This is the front face and this is the area where the wheel would attach to the car
on this face here.
The shape of this disc means that the air actively wants to travel through the inside
of the disc which is what is giving us our cooling.
Once that air has passed through the disc, it exits out through here and finds its way
out through the wheel and into outer stream.
The style of these veins and how open the wheel is and the wheel design
actually can have quite a big impact on how well the brakes are cooled.
Here we've got a relatively typical example of how a brake duct would attach to the
upright of the car to feed air to the disc.
This particular plate has an area cut out of it for where the brake calliper and
everything sits which tends to seal this part of the disc and it's not quite the
right size but normally this plate would extend to cover that full inside face of
the disc and also block off this area.
We would have a hose connected to this duct and we can see how the air is going
to flow in from that duct and into this area of the disc which is where we want to
direct the airflow to get these veins working.
It's pretty important when designing this whole system, make it the easiest path
to get in, once the air is in here, to pass all the way through.
What we don't want is to have air being ducted to this area and then not doing
a good job of sealing it in here.
Once the air's in, we want it to be forced into these veins and to help it pump
out through the disc.
The layout of the suspension where your brake calliper sits, how the upright package is with
the rest of this duct will determine the exact shape of this.
But essentially we want as much as practical for this whole surface to be relatively sealed
so when we send air in here, it's forced to go out where we want it out through
these veins.
One of the critical elements when designing a brake cooling system is the sizing of the
ducts or the area of air you're passing air through into this section of the disc.
It's not unheard of in professional racing certainly in large heavy cars designed
for really high speed to have three, four inch ducts or even multiple four inch
ducts of air feeding air into this area of the disc to maximise the cooling.
One of the challenges with connecting an air source to anything that's part of the
suspension is that particularly on the front, not only is the suspension going up
and down but you've also got the front wheels turning.
This particular style of hose is designed for motorsport brake cooling.
It does need to have quite a high temperature rating to be able to survive in a high
temperature area like the brakes.
It also needs to be able to have a decent amount of articulation.
It is worth spending the money on getting good quality hose to do this job.
Trying to cut corners on the hose is not a great idea because it is quite a hostile
environment for the duct to work.
This is an example of a way a brake duct system can be packaged on a car.
So we've got some ducting hose connecting to this vent at the front area of the car.
Can see this travels through, is bolted to the chassis here, runs behind the suspension
and connects to this duct which is bolted to the back of the brake disc.
As you can see here, the duct has to go through quite a strange shape.
It keeps a constant cross section but it does flatten in.
That's because when the wheels are turned, the tyre will be in this area so you need
enough clearance for the brake duct to pass through without the tyre actually coming into
contact with any of the duct.
It's actually quite a big challenge to package all of the ducting on the inside in a guard
like this.
Space is always at a premium.
As we can see here, there's not a lot of room.
Particularly when you allow room for all of the suspension to move up and
down as it needs to.
And you don't want to brake duct coming into contact with any suspension components
because it will chafe and eventually you'll get a failure there.
When you're looking for a place to feed that cold air from to cool the brake system,
it is pretty important to consider where you take it from at the front of the car.
Wherever you take your cold air from, you need to try and take it from as high
a pressure area as possible.
That usually means somewhere on the front face of the bumper where you've got a
relatively direct line in for the air to go.
When sizing these ducts, you typically want to go on the larger side than the smaller side.
The reason is with different ambient conditions or how closely you're following
other cars on track, it will change your brake cooling requirement so what you typically
do is start with quite a large duct and you blank it down to the conditions of the day.
So if you start with a three inch duct you may, if it's mounted to the front of the car,
that can be as simple as adding tape across the face to allow more or less airflow into
the duct or it can be more sophisticated with precut sections that quickly can be
swapped in and out of the front of the duct to tune your blanking.
If you're using aftermarket brakes, your brake supplier will be able to give you the
ideal operating window for your brakes that will be a minimum and a maximum
temperature, the minimum being the temperature the brakes need to be at
before you can start using them hard on track, the maximum being the highest
safe operating temperature for them and in the middle is where you want to be
operating all the time when you're racing hard on track.
There are a few different ways you can measure the temperature of the braking
system, usually that means checking the temperature of the disc.
Most often this is done with infrared temperature sensors on the disc surface
or with brake temperature paint, I'll show you what that's about now.
So here we've got an example of an infrared temperature sensor.
This particular one is a Izze Racing sensor.
In the front surface is where you've got the infrared sensing element and the idea
is it is packaged close to the disc and looking at the disc surface.
The manufacturer of the sensor will give you a working range for how close it
needs to be packaged to the disc and what the operating window is.
This particular sensor has a 60° window where it can sense temperature so that
means from the surface of the temperature here, you draw a 60° arc out from the face.
That 60° window will define the proximity the sensor must be within the disc for it
to be able to see the entire disc surface.
A more old school but certainly very effective and still relevant way of checking
your brake disc temperatures is by using temperature paint.
The idea with this is this paint changes colour at a certain temperature range.
So in this case the green will change colour at a lower temperature and the red
will change colour at a higher temperature.
It's really only giving you a single point of information.
When you run the car on track, once this has changed colour it's not going to change
again but at least it gives you a read on the approximate operating temperature
you've got on track to see if you're wildly below or wildly outside the window.
What's typical is your brake supplier will tell you that the brakes must be hot enough
that they're operating such that the green paint starts changing colour but that the
red would not.
So that is your safe window so you know if the green hasn't changed colour,
the brakes are running too cold and you might need to reduce the amount of cooling by
adding blanking.
Or alternatively if they're running too hot and the red is changing colour, you need to find
a way to cool the brakes more for the brakes to work effectively and safely.
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