Siping is a process of cutting thin slits across a rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

 surface to improve traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...

 in wet or icy conditions.

Siping was invented and patented in 1923 under the name of John F. Sipe  The story told on various websites is that, in the 1920s, Sipe worked in a slaughterhouse
A slaughterhouse or abattoir is a facility where animals are killed for consumption as food products.Approximately 45-50% of the animal can be turned into edible products...

 and grew tired of slipping on the wet floors. He found that cutting slits in the tread on the bottoms of his shoe
A shoe is an item of footwear intended to protect and comfort the human foot while doing various activities. Shoes are also used as an item of decoration. The design of shoes has varied enormously through time and from culture to culture, with appearance originally being tied to function...

s provided better traction than the uncut tread. Another story is that he was a deckhand and wanted to avoid slipping on a wet deck.

The process was not applied to vehicle tires on a large scale until the 1950s, when superior tread compounds were developed that could stand up to the siping process. On roads covered with snow, ice, mud, and water, sipes usually increase traction. A US patent to Goodyear claimed sipes improve tire traction as well, and tend to close completely in the tire "footprint" on the road. A 1978 study by the US National Safety Council found siping improved stopping distances by 22 percent, breakaway traction by 65 percent, and rolling traction by 28 percent on glare ice.

Tire tread block shapes, groove configurations, and sipes affect tire noise pattern and traction characteristics. Typically, wide, straight grooves have a low noise level and good water removal. More lateral grooves usually increase traction. Sipes are small grooves that are cut across larger tread elements. Up to a point, more sipes give more traction in snow or mud.

As is often the case, there are compromises. Winter tires, and "mud and snow" tires, may have thousands of sipes and give good traction. But, they may feel "squirmy" on a warm, dry road. Treadless racing "slicks"
Slick tire
A slick tyre is a type of tyre that has no tread pattern, used mostly in auto racing. The first production "slick tyre" was developed by a company called M&H Tires in the early 1950s for use in drag racing...

 on dry roads give maximum traction. These have no sipes, no grooves, and no tread blocks. They also have very poor traction however on even slightly wet surfaces. Tire manufacturers use different tread rubber compounds and tread designs for different tires' usages.

Large sipes are usually built into the tread during manufacturing. Sipes may also be cut into the tread at a later date, called "microsiping". Bandag developed a machine for microsiping which places a curved knife blade at a slight angle on a rotating drum. The drum is placed so when it is pressed against the tread the tire is pressed into an exaggerated hollow, as if driving down a rail. The drum is lubricated and rotated and the knife makes a series of diagonal cuts across the tread. For improved traction, the tire may be siped twice, leaving diamond-shaped blocks. A significant problem with field siping is that the tread picks up rocks, glass, and other hard road debris in use, and even with thorough cleaning the knife service life is often poor.

Microsiping can dramatically improve tire traction in rain and snow. However, microsiped tires may also have increased road noise and tire wear when operated on dry surfaces. recommends against adding more than "the sipes that your tires come with" because of longevity and dry performance.
Some companies such as Les Schwab
Les Schwab
Leslie Bishop "Les" Schwab was an American businessman from Oregon. He was the founder of Les Schwab Tire Centers, a company which Modern Tire Dealer called "arguably the most respected independent tire store chain in the United States." A native of Oregon, he served in the U.S...

 claim that microsiped tires reduce tire friction heat and tire wear and extends the life of the tire.

In Massachusetts in the 1970s, it was legal to operate a school bus with bald tires, provided they were double microsiped.

Both Bridgestone
The is a multinational rubber conglomerate founded in 1931 by in the city of Kurume, Fukuoka, Japan. The name Bridgestone comes from a calque translation and transposition of ishibashi, meaning "stone bridge" in Japanese....

 and Michelin
Michelin is a tyre manufacturer based in Clermont-Ferrand in the Auvergne région of France. It is one of the two largest tyre manufacturers in the world along with Bridgestone. In addition to the Michelin brand, it also owns the BFGoodrich, Kleber, Riken, Kormoran and Uniroyal tyre brands...

 sell snow tires that are siped at the factory, while Saf-Tee Siping and Grooving sells machines that can sipe most standard vehicle tires. Siping can also be done by hand. Be aware that siping the tires can void the manufacturer's warranty.

Note: Claims that extended life is achieved by siping may only apply to certain environments, operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...

s and rubber compound builds.

External links

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