Tyre Sipes & Siping
Sipes are tiny slits in the tread blocks that run
across the width of many winter tyres. The sipes are
typically positioned at approximately every 5mm all the
way around the tread of the tyres and so greatly
increase the number of lateral edges. In accelerating
or, more importantly, braking these leading edges bite
into the road surface and add to the tyres ability to
grip.
In the United States sipes are often added,
post-manufacture, in tyre depots and is frequently used
on all season tyres as well as winter tyres. Specialist
machinery is available there that executes this
procedure on both new and partly worn tyres. However
some tyre manufacturers regard the process as a
violation of the terms of warrantee and in Europe the
practice is illegal because it falls within the
legislation that prohibits re-grooving of car tyres.
The process of siping was patented by John Sipe in the
USA in the 1920s. Initially to improve the grip of
rubber shoes in the wet conditions in a slaughterhouse.
It began to be applied to car tyres in the United States
in the 1950s, when superior tread compounds for tyres
were developed that could stand up to the siping
process.
On roads covered with snow, ice, mud, and water,
sipes significantly increase the grip of most tyres. The
sipes tend to close up as the tyre tread comes into
contact with the road so the tyres actual “footprint”
remains unchanged. A 1978 study by the U.S. National
Safety Council found that, on ice, siping improved
stopping distances of tyres by 22 percent, breakaway
traction by 65 percent, and rolling traction by 28
percent.
However while siping can dramatically improve the
traction of tyres in rain and snow it can increase the
road noise in dry conditions.
Most of the etyres range of winter tyres are
manufactured with heavy siping.
See Also:
Glossary on Sipes |
