32 FORMULA E BRAKES
›The 2018-19 season (Season 5) was a pivotal one
for FIA Formula E. It was the fi rst season to feature
the new Gen2 car, whose McLaren-supplied battery
enables drivers to complete a full race without a chassis
change for the fi rst time.
The Gen2 car – offi cially named the Spark Racing
Technology SRT05E – is used by all teams in the series and
features a friction braking system developed by Brembo
to work in conjunction with regenerative braking from
the electric powertrain. This carbon-carbon ‘spec’ friction
braking system comprises discs, pads, calipers and a
single-stage tandem pump.
“It has been a complex challenge for us,” says Brembo
race engineer, Giovanni Clemente. “We must supply the
same system to all 11 teams, ensuring equal service and
performance, but on the other side we must also be able
to tailor our technical support to the different needs that
can arise from individual teams and drivers.”
Of particular note was the need to size a single system
that could handle a very wide working range. On a track
that’s easier on the brakes and perhaps even wet, with
100% regeneration deployed there are times when the
rear axle is barely using the friction materials at all to
VehicleDynamicsInternational.com • November/December 2019
brake. On the fl ipside, a qualifying lap on a tough track
with no regen deployed will push the rear brakes to the
top of Brembo’s suggested working range – up to 800°C
(1,472°F), rather than the more typical 400-500°C
(752-932°F).
From a hardware point of view, only the cooling duct
blanking on the front axle is adjustable, so there’s much
to be gained from development work on control strategies
and the mix of friction and re-gen braking.
“Most of the fl exibility for the teams is in the re-gen
logic and in the way the rear axle is actuated,” says
Clemente. “They can choose the amount of energy that
should be regenerated to recharge the battery, and how
much to dissipate through the friction material. At the
same time, they can also do tricks like merging between
the re-gen and the friction material, or defi ne a more
aggressive or softer approach to the braking. They can
also play with the pressure to be applied on the brakes,
depending on temperature.
“The teams are different in the budgets that they have
available,” he expands. “There are those that have more
money to test different parts, spend many hours on the
benches and rigs, and research strategies and control
ABOVE: The front calipers
use 30-36mm pistons, with
26-28mm pistons at the rear.
The calipers are billeted from
a single block of oxidised
aluminium alloy. Each front
caliper weighs 1.2kg (2.6 lb)
and each rear caliper is
1kg (2.2 lb)
RIGHT: The front discs are
24mm thick and the rears
20mm thick. The front pads
are 18mm thick and the rear
pads 16mm thick. There are 70
ventilation holes in the front
discs (6.2mm diameter) and 90
in the rear (4.2mm diameter)
/VehicleDynamicsInternational.com