- Accurately knowing the ride height of your car as it moves around the circuit
can be extremely useful.
This is particularly true if you've got a car that generates a lot of downforce with
its floor because the ride heights at both the front and rear of the car have a huge effect
on how much downforce each end of the car makes.
The traditional method for determining ride height is to use damper pots.
That's where you're measuring the displacement of the suspension and from that you can make
a calculation to infer the ride height.
There are a number of sources of error when it comes to determining the ride height using
damper pots.
One of the main ones is deflection of the tyres.
This vertical displacement of the tyres does have quite a significant effect on the ride height
of the car.
One way to measure ride height more accurately than using damper potentiometers is to use
laser ride height sensors.
This is a sensor that's mounted to the chassis and directly measures the distance between
the sprung mass and the road surface.
This is an example of a laser ride height sensor, this particular one is an Izze Racing
product.
At one end of the sensor we've got the electrical connection so this is designed to
work over a CAN bus.
You've got a ground and a positive pin as well as a CAN high and a CAN low pin.
And then one of these five pins which is actually unused.
Underneath the sensor, this is the face, this face here would actually face the road.
This is where you've got the laser and the receiver.
So the laser projects out a beam and then the angle of reflection which is what the
receiver picks up, this is how the sensor calculates the ride height that it's
running at.
Typically you would want to have this rigidly mounted to the car.
One of the things the manufacturers do recommend, if it's in a place of high
vibration, that it should be isolated from vibration to avoid problems with the
measurements.
Typically you would have three of these sensors mounted to the car.
Because you can treat the chassis as a plane, you only need to take a measurement
in three separate points and that completely defines that inclination and the height of
each point of that plane.
The most common way to lay these out would be to have two laser ride height sensors
at the front and one in the rear.
One of the reasons for that is because the front of the car tends to be more sensitive
to ride height, that's the end of the car you want to have the highest quality measurement.
So you would tend to have the sensors as far outboard and as far forward as possible
and the rear one would typically be mounted in the centre somewhere towards the rear
of the car.
There are a few practicalities you need to consider when choosing and setting up a
laser ride height sensor.
One of the is that the sensor itself should be kept as parallel as possible to the ground
so this surface faces down and it should be mounted such that this surface is parallel
with the lowest surface of the car.
Another things to consider is that each sensor has a specific ride height measurement range.
So for this particular sensor, it's somewhere in the range of between 30 and 300 mm.
That means that the road surface must stay within that range for you to be able to get
accurate measurements.
Where the laser beam is projected onto the ground, that needs to be in a place where
there's no direct sunlight.
That's because the sensor has trouble picking up the signal if it's in direct sunlight
because the reflection isn't as strong.
When you place them in the car, particularly In the front you generally want them as far
outboard as possible to give you the most accurate measurement of that plane.
One last thing to consider when you're deciding where to place these on your car,
is that ideally you'd keep them away from high heat sources.
One of the reasons there apart from actually damaging the sensor is that thermal distortion
in the air underneath the car can lead to measurement errors.
The advantage of using a laser ride height sensor is that you're directly measuring
the pitch, the roll and the heave movement of the sprung mass with respect to the road.
If you're doing something like building an aero map for you car by running it through
a whole lot of different ride height and heave combinations and have a way of measuring
the aero forces.
Having laser ride height is really important because it really builds up an accurate aero
map for your car.
Being able to directly measure the ride height of each point of your car with something like
a laser ride height sensor can be extremely useful.
And it certainly has a lot of advantages over traditional methods like damper pots.
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