Mazda Training manual — part 83

Dynamic Driving Safety Systems

Fundamentals

•

Even if the vehicle does not skid, an accident may result, because it is not possible for
the driver to steer around an obstacle with locked wheels.

L2003_01009

•

The brake pressure regulation of the ABS prevents the wheels from locking-up. It applies
the correct brake pressure to all brake callipers to maintain the vehicle’s steerability
while simultaneously achieving a short braking distance.

L2003_01010

Curriculum Training

01-11

Fundamentals

Dynamic Driving Safety Systems

Electronic Brakeforce Distribution

•

On former vehicles, only mechanical solutions were used for brakeforce distribution
between the front axle and the rear axle. One of the disadvantages was that, to avoid
early wheel lock-up under all circumstances (e.g. due to wet or slippery roads), the brake
pressure applied to the rear wheels was never optimal.

•

Now all Mazdas with ABS also have EBD, which allows the brakeforce distribution
between the front and the rear axles to be adjusted based on actual conditions.

•

Under most conditions the proportion of the brakeforce applied to the rear wheels is
increased, resulting in optimal vehicle stability during all conditions. This results in:
reduced braking distance, reduced thermal stress to the front brakes, and evenly worn
front and rear brake pads.

•

While a standard vehicle had a brakeforce distribution of approx. 80 % to the front
wheels and 20 % to the rear wheels, the brakeforce distribution for vehicles with EBD
changes up to approximately 60 % to 40 % (variable).

01-12 Curriculum

Training

Dynamic Driving Safety Systems

Fundamentals

•

The illustration shows the differences in applied brakeforce between a vehicle with fixed
brakeforce distribution and with EBD.

L2003_01011

X Brakeforce applied to the front wheels

3 Ideal brakeforce distribution on the

unloaded vehicle

Y Brakeforce applied to the rear wheels

4 Brakeforce distribution on the unloaded

vehicle with EBD

1 Ideal brakeforce distribution on the fully

loaded vehicle

5 Brakeforce distribution with proportioning

valve (unloaded and fully loaded)

2 Brakeforce distribution on the fully loaded

vehicle with EBD

Curriculum Training

01-13

Fundamentals

Dynamic Driving Safety Systems

•

The first portion of the illustration (areas 1 and 2) shows the range of wheel slip where
the EBD and ABS operate. The remaining part of the illustration shows the conditions of
less than optimal brakeforce / steerability.

L2003_01006

X Wheel slip

2 ABS operation range

Y Coefficient of dynamic friction

3 Instable driving condition

1 EBD operation range

4 Locking wheel

01-14 Curriculum

Training