Automotive Engineering - July/August 2019 - 12

TECHNOLOGY REPORT

Michelin, GM partner on airless
wheel for 2024

Closeup of
Michelin's
"airless"
Uptis wheel
mounted on
a Chevrolet
Bolt EV.
Michelin has partnered with General Motors to test the tire company's "airless" wheel technology, which will it says will improve
safety and reduce waste by eliminating the possibility of punctures. The two companies expect to begin marketing the Uptis
(Unique Punctureproof Tire System) Prototype in 2024.
The novel structure, which has been long in development
and is covered by about 50 patents, is made with aluminum,
rubber components and resin-impregnated fiberglass, Eric
Vinesse, Michelin's executive VP of research and development,
explained. Michelin's technology will be tested on a fleet of
Bolt EVs beginning this year.
The airless structure eliminates the possibility of blowouts,
improving safety and ensuring that drivers won't be stranded
by flats. Vinesse, speaking at the 2019 Movin'On Summit in
Montreal, estimated that 200 million tires annually are discarded prematurely due to punctures.
Michelin plans to start production in North America, but
Vinesse said benefits may be greater in other geographies.
North American drivers typically have tire punctures every
two or three years, while punctures occur every six to eight
months in China.
Uptis wheel assemblies can be built to different performance orientations, such as sport or comfort. They also can
be tuned to specific vehicles. The design-marketed as
Michelin X Tweel-already is in production for a variety of
commercial off-road vehicles, from skid-steer loaders to golf
carts, all-terrain vehicles (ATVs) and garden tractors.
Vinesse said there will be several technical improvements in
the automotive-applications' design between now and 2024,
when production begins. During that time, regulators and
standards bodies also will have to develop new nomenclature
and make other changes to address the non-inflatable tires.
Uptis weighs about 5% more than conventional tires, but that
weight will be offset because no spare tires will be needed on
the vehicle, according to Vinesse. The number of retread cycles
will be determined as physical tests are performed.
The wheel assemblies can be easily retreaded, helping reduce longterm costs, but initial pricing isn't yet determined.
Terry Costlow

12 July/August 2019

PROPULSION

SF90 is Ferrari's first-ever
plug-in hybrid
Storied sportscar-maker Ferrari will produce its first-ever plug-in
hybrid-electric vehicle, the company said in announcing its SF90
Stradale, a new model named in reference to the 90th anniversary of Ferrari's founding. But not only is it the brand's first
PHEV, it's the most powerful Ferrari production car ever sold.
And for yet another "first," the SF90 Stradale is the first
Ferrari sportscar to be fitted with all-wheel drive (AWD), "a
step necessary to allow the incredible power unleashed by
the hybrid powertrain to be fully exploited," Ferrari reported.
"The new model is extreme on every level and represents a
true paradigm shift because it delivers unprecedented performance for a production car," Ferrari said in a release announcing the car. The company also confirmed that with the inception of the SF90 Stradale, "a V8 is the top-of-the-range model for the first time in the marque's history."
The SF90 Stradale combines the output of a 4.0-L twinturbocharged V8 (essentially derived from Ferrari's muchawarded 3.9-L twin-turbo V8) and three electric motors-a
motor/generator between the engine and the transmission
driving the rear wheels and a motor for each wheel at the
front axle, which in true "e-axle" configuration is not mechanically connected to the internal-combustion driveline. The
arrangement is central to imparting the sophisticated AWD
propulsion that combines control of the two front-axle traction motors with the IC/motor-driven rear wheels.
The SF90 Stradale's performance is little short of astounding-even by Ferrari standards. The company claims a 0-62
mph (100 km/h) acceleration time of 2.5 s and says the car
can attain 124 mph (200 km/h) in 6.7 s, while top speed is a
claimed 211 mph (340 km/h).
Despite the added weight of three motors and a 7.9-kW-h
lithium-ion battery pack-total hybrid system weight is 270
kg (595 lb)-Ferrari said the 2-seat SF90 Stradale's curb
weight is just 1570 kg (3461 lb).

Eight cylinders for the primary job

The SF90's 4.0-L 90-degree V8, developing 769 hp at 7500
rpm, has the highest output ever for a Ferrari V8, the

The SF90
Stradale not
only is Ferrari's
first-ever
plug-in hybrid,
it's also the
first Ferrari
sportscar to be
fitted with allwheel-drive.

AUTOMOTIVE ENGINEERING

FROM TOP: GM; FERRARI

CHASSIS

Automotive Engineering - July/August 2019

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