 Michelin
have launched what they claim to be a completely new innovation
in tyre technology with their new Pax System, which enables
a driver to be in full control of his vehicle even after sudden
pressure loss such as a puncture.
The system consists of four interdependent elements: wheel
(rim), tyre, support ring and pressure loss or run-flat indicator.
The principle feature of the Pax System is the way the tyre
is anchored on the rim. A conventional tyre is held in place
mainly by its pressure but the Pax System achieves a secure
seat of the tyre bead on the rim with the help of a wedge
shaped rubber element inside the casing that clamps into the
rim. Any force working on the tyre only drives the wedge more
firmly between rim and bead wire, thus ensuring the secure
seat of the tyre on the wheel independently of the pressure
inside the tyre.
 The
inner and outer nominal diameters of the Pax System wheel
differ from one another, thus making fitting the tyre and
support ring easier. On the tyre changer they are pushed on
the rim from outside like conventional tyres and pressed on.
The larger inner diameter of the wheel allows more space for
brake system and axle construction.
Apart from its anchoring the Pax System tyre’s casing
is similar to Michelin’s high performance tyres. The
construction principle allows shorter sidewalls consisting
of the flexing zone only, eliminating the superfluous bead
area. Therefore the tyres do not have the conventional balloon-like
shape and the section and contact area are optimised accordingly.
Because of the construction of the rim of the sidewalls of
the tyre are of different heights so the Pax System tyre has
an outer and and inner side and is therefore irreversible.
The Pax System support ring which carries the weight of the
vehicle when no pressure remains in the tyre, consists of
a rubber element with a thickness of several centimetres and
a width of almost the same as the tread. The support ring
rests directly on the rim.
A pressure loss or run-flat indicator has been developed
which uses pin-point reinforcements of the support ring to
create special rolling frequencies in the tyre. Sensors pick
up vibrations in the support ring, and the central computer
of the vehicle sets off the puncture warning in the cockpit.
Performance After Pressure Loss
 Michelin
state that in the event of a puncture, even with sudden total
pressure loss, vehicles fitted with the Pax System can be
controlled safely because of the way the tyre is anchored
to the wheel and because the support ring resting on the rim
takes over the basic functions of the tyre. The company guarantees
a range of 200km at a maximum speed of 80 km/h with zero pressure.
This gives the driver time to leave a danger zone such as
a tunnel and choose for himself the time and place of the
tyre change.
Improved Handling
The firmer anchoring in the well of the wheel and the shorter
sidewalls improve handling. Rolling resistance also benefits
from the shorter sidewalls because less material is flexed.
Michelin evaluates the improvement over other tyres with optimised
rolling resistance at approximately 10%, with a resulting
further reduction in fuelo consumption and emissions of 1-2%.
Pax System Can Cope with Heavy Loads
A further advantage of the Pax system'sconstruction is the
ability to carry a greater load. The Pax System benefit of
lower tyre profiles means larger inner diameters of the wheels
and thus larger brakes or integrated systems. In cases where
larger brakes are not needed, smaller outside wheel diameters
will have the advantages of smaller wheel-housings and more
available space in the car interior. However the optimum benefits
of the Pax System cannot be experienced unless its qualities
are taken into account at the design stage of vehicle.
System Already Being Used by Manufacturers
AUDI have already exhibited an A8 featuring the Pax System
at the German International Motor Show. At the same show Pininfarina
presented a town car design named Metro-cubo with different
front wheel and rear wheel sizes and no spare wheel. Mazda
displayed the Neospace which uses the Pax System in addition
to which Citroen also use it on several vehicles: Pluriel,
C6 Lignage and C3 Lumiere. In France, the sports prototype,
Cadillac Evoq, was test driven by journalists this summer.
This also has two different tyre sizes and uses the space
vacated by the spare wheel to house the hood of a converted
hard top.
Michelin say that several car manufacturers have projects
in progress involving the Pax system and the company has made
an agreement with Pirelli concerning the further joint development
and subsequent marketing of the system.
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