This lesson examines the difference between mechanical grip and aerodynamic grip and how they affect braking consistency and pressures during threshold braking.

Mechanical Grip

Mechanical grip is purely the way of the car being thrown around the track. On a flat surface, it remains pretty consistent. On tracks with elevation changes or alterations in camber, the mechanical grip is going to be dramatically effective.

Aerodynamic Grip

When at high speeds, air collides with the car interacting with the body in many ways, depending on its characteristics. It can create drag, slowing down the car, and lift like an airplane, or downforce sucking the car onto the track.

A lot of downforce is created on a high performance race car, pushing it down and strengthening its interaction with the track. What's amazing about downforce is that the car has a lot more contact with the track as if it was more massive, but without the bad effects of inertia preventing the car from turning more. This improves drastically the ability of the car to turn around.

Downforce and Mass Example

For example, a 1000 kilo car with 1000 kilo of downforce produces the equivalent compression at the tire contact patch of 2000 kilo. When turning, braking, or accelerating, the inertia only applies to the actual mass of the car, 1000 kilos. That's why it's able to turn so fast.

If you got a car that has more downforce than its own weight, it would theoretically be able to drive upside down in a tunnel without falling. But don't try this at home, please.

Downforce and Speed Relationship

Downforce levels change according to speed. At super high speeds, the downforce can even double the braking pressure that the car can handle. At this point in time, the tires feel as if the car is, say for example, twice as heavy. So if this car is 1000 kilo, right now the tires are supporting 2000 kilos. But as that speed goes down, this value also quickly goes down, decreasing the total force between the tires and the track.

Variations in Grip Under Different Conditions

There are variations in grip we can have in different situations, combining changes in both elevation, which would affect the mechanical grip, and speed, which would affect the aerodynamic grip.

Key Differences

• The aerodynamic forces are quite consistent with speed. Speed goes up, downforce goes up, speed goes down, downforce goes down.

• The mechanical grip, though, can change drastically with elevation changes.

Adjusting the braking in different elevation changes will be covered in a specific lesson for that topic.