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Tyre Tests News 6Feb06:
Continental recommends tyre-testing change
Does Form Still Follow Function, or Tyre Testers?
Continental recommends tyre-testing change
During the course of Continental’s annual pre-Christmas
event, which has now taken place for more than 10 years,
the German manufacturer asked international tyre
specialists from several reputed magazines to ponder the
following question: “Do driver assist systems require
new winter tyre testing procedures?” To summarise the
stimulated discussions that took place in Ivalo,
Finland, it seems development engineers at Hanover are
obliged to try and serve the two masters at the same
time.
On the one hand, all tyre manufacturers are interested
in achieving good test results for their products. On
the other hand, tyre features have to be optimised
according to road realities. And this is exactly where
Continental has detected a discrepancy: because of the
introduction of new driver assist systems some test
set-ups seem to be out-of-date and could therefore
generate misleading results.
Driver assist systems like ABS, ESC and TCS are now
common standard fitments, even on compact cars. They
provide increased safety and intervene to correct
driving errors. During tyre testing, however, ESC and
TCS are switched off in order to test the tyres without
the effects of those systems. But such test methods have
now reached their limits – particularly when you
consider that ESC cannot be switched off in some
vehicles without interfering with the electronics.
Transferability of the test results therefore also
debatable because – depending on the vehicle
manufacturer’s philosophy – driver assist systems have
different performance parameters and so respond in
different ways to different tyres grip characteristics.
According to Dr Burkhard Wies from Continental, driver
assist systems should also be switched on during tyre
testing in the future. This would keep tyre tests in
line with latest technological advances for both tyres
and vehicles.
Recent years have seen a significant increase in the
number of cars equipped with systems like ABS, ESC and
TCS. After being launched in 1978, it took about 20
years for ABS to be represented in 40 per cent of all
new cars. The ESC stability system, introduced in 1995,
has now also reached a 40 per cent share of all newly
registered cars – from the top category right down to
the compact size. So, equipping cars with electronic
management systems has accelerated quite substantially.
Is it still realistic to conduct tests without ESC?
Usually these systems are deactivated for the sake of
comparability of test results. But, testing tyres
without these systems may no longer be state-of-the-art,
says Dr Burkhard Wies, head of passenger car winter and
replacement tyres development at Continental in Germany:
“Without ESC and TCS the transferability of tyre test
results to modern vehicles cannot be guaranteed owing to
the fact that driver assist systems respond
differently,” he states. “Braking with ABS has been part
of the standard test programme since 1990. So it’s now
time to consider incorporating the other driver assist
systems into tyre evaluation procedures as well.” After
all, in some cars neither the ABS nor the ESC system can
be switched off anyway.
His proposal is supported by methods normally employed
by some vehicle manufacturers when conducting tyre
approval tests with the driver assist systems switched
on: “There is also a huge difference in the results of
winter tyre tests performed on vehicles with and without
traction control systems,” he explains. “In fact the
results were reversed depending on whether or not
traction control was engaged.” Tyres for vehicles
equipped with ESC should really be adapted to the
vehicle electronics in future – and could indeed be
quite different to tyres for vehicles lacking driver
assist systems.
“Tyre and vehicle testers should react to these new
developments by adapting their tests accordingly,”
advises Dr Wies. “And the first step in this direction
would be to include ESC in future tyre testing
procedures.”
There are a high number of options available to test
engineers when testing tyres with the ESC activated:
different conditions of road, curve radii and propulsion
concepts should all be taken into account, advises Dr
Burkhard Wies. “Our engineers can meanwhile draw on a
tremendous amount of tyre testing experience, and yet we
shall still discuss together with test experts from
professional motor magazines new methods of testing with
ESC in order to obtain objective results.”
An Outlook Into The Future:
Developments to improve driving safety and avoid injury
to persons are automatically leading to greater
networking of safety-related automobile electronics.
Chassis and tyres are delivering more and more safety
reserves, measuring systems are able to detect the
condition of the road and warn the driver of
insufficient distance to the car in front, stability
control systems and passive safety devices are being
linked up to one another. In a hazardous situation,
pressure within the brake system is already increased
prior to brake actuation, seat belts are tensioned and
the airbags made ready for release.
With today’s safety systems, however, development has
not yet reached its peak according to Dr Wies, head of
passenger car winter and replacement tyres development
at Continental in Germany. The OFE (Online Friction
Estimation) prototype car from Continental Automotive
Systems, for example, measures the road temperature, the
rain or snowfall, the steering angle and the individual
wheel speed. The car’s electronics then “estimate” the
expected amount of slip and warn the driver that the
road is dangerously slippery. In combination with an
advanced navigation system, the car first alerts the
driver on the basis of detected road conditions that he
is driving too fast into a bend, and, in a second step,
tells him to activate the brakes. If the driver fails to
respond, the system can in future actively intervene and
reduce the speed to ensure safe cornering.
“Thanks to the smart networking of sensors and vehicle
control systems this prototype helps give a dramatic
improvement to safety, particularly on slippery roads,”
says Norbert Kendziorra, project manager for the
development of the OFE prototype at Continental. |
