Continental's Eco-Contact CP low rolling resistance
tyre provides extra safety in the wet and lasts
longer
The Firestone Fuel Saver, pictured here in F-580
format, is also available as the 65series, H and
V rated FH680 and the V rated FH690 in 55 and 50
series
The Michelin Energy is claimed to be able to
save 5% in fuel bills
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Green Tyres, Fuel Saver Tyres, Low-Rolling
Resistance Tyres - They are all basically the same
thing and refer to the performance advantages gained
by adding silica to the tread compound of tyres, the
key advantage of which is the ability to reduce fuel
consumption whilst maintaining performance critical
qualities such as wet grip. Tyres incorporating silica
have been on the market for a few years now although
silica has really only become widely incorporated
into tyre design strategies within the last couple
of years or so.Although the use of silica is now widespread,
its use by pioneers such as Michelin in the Michelin
Energy and Continental in the ContiEcoContact CP and
EP tyres was considered to be a true breakthrough
in tyre technology. But why are low rolling-resistance
tyres so revolutionary in their design and what benefits
do they offer the consumer?
Solving the Compromise
A major problem facing tyre designers has traditionally
been solving the compromise between low rolling
resistance and wet grip. Rolling resistance is the
amount of energy a tyre absorbs as it revolves and
deflects. The lower the rolling resistance the less
fuel is required to propel the vehicle forward.
Lowering the rolling resistance, however, has traditionally
meant a reduction in wet grip performance, which
of course is unacceptable.
This problem has been solved by the replacement
of certain quantities of carbon black with silica
in the tyre's tread compound which has enabled manufacturers
to produce tyres which provide improved wet skid
properties, better winter performance and lower
rolling resistance all at the same time.
The Technology Explained
The reason why this technology has been considered
to be so revolutionary is best described as follows;
Grip is affected by the degree to which a tyre
is distorted at high frequencies - in other words
the degree to which it hits small stones and unevenness
in the road surface. Grip is also best served by
rubber compounds which absorb high levels of energy
(high hysteresis compounds).
Rolling resistance, on the other hand, is affected
by low frequency distortion - the deflection of
the tyre as it revolves. It also requires compounds
which absorb low quantities of energy (low hysteresis
compounds). This contrast is why it has been impossible
in the past to provide tyres which both reduce rolling
resistance and increase wet grip.
With the addition of silica, however, tyre engineers
have been able to produce compounds which are high
hysteresis at high frequencies but low hysteresis
at low frequencies.
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