Cutting into tire traction

by Steven Macleod

CALGARY, Alta. – The larger the surface area of a tire in contact with the ground surface, the better the traction of the vehicle.

This is not new news, but tire traction is still an important issue especially as the elements turn and truckers are faced with roads covered in snow, ice, rain, mud and gravel; sometimes all in the same day during a typical Canadian winter.

To provide the traction necessary for a truck to stay between the painted lines on the highway, some commercial tires are manufactured with sipes as part of the tread design. These sipes aim to provide increased traction by creating more pieces of the tread block that contact the ground surface.

“All that’s doing is causing the tread to have more biting treads,” explained Guy Walenga, with Bridgestone/Firestone. “Siping creates a lot of edges and it’s those edges that bite through the moisture and get down to the pavement.”

The original idea of siping dates back to the 1920s and involves a pair of shoes rather than tires.

“Siping was patented in 1920 by John Sipe, a slaughterhouse employee, to provide better traction on the slaughterhouse floor making shallow cuts on his shoe soles,” remarked Jim Nespo, with Goodyear.

Although tire sipes can be found on newly-manufactured tires, the process has developed further into an aftermarket option. The practice of tire siping (cross-cutting or skiving) creates additional traction in the tire tread by cutting thin slits in the existing tread, which creates more tread pieces.

“The process is to put additional sipes beyond what the manufacturer provides on the original tread sculpture. They’re kind of like cat claws opening up to provide traction,” explained Greg Cressman, with Yokohama. “It opens up the tread and provides additional grip. There are certain weather conditions when you have the need for additional traction and you can add sipes.”

As well as additional traction for drive tires, siping can have an impact on the wear of trailer tires.

“If it’s done on a drive axle tire it’s to provide traction,” said Ralph Beaveridge, with Michelin. “Also on trailer tires they can be faced with irregular wear and this can help avoid the onset of irregular wear. I don’t know the science behind it, but I’ve seen the results.”

There is how-to literature available for the do-it-yourselfer, but it would require great skill to make the proper incision each time the tool cuts into the rubber. Major tire manufacturers all advise against a backyard job.

“There is a risk involved with anyone using cutting tools on a tread design,” noted Beaveridge. “When we design a tire with siping it is designed to balance traction and wear to offer the best value to our customers. After the fact when you give someone a cutter and say make some crosscuts, they could be experienced or not.”

Specific machines have been developed to provide aftermarket siping to tires. A tire shop offering tire siping will then be able to place the tire on the machine and have the work automatically done.

“Tire siping consists of making 1/4-inch deep cuts 1/2 an inch apart around the tire,” commented Nespo.

“Since most commercial traction tires provide adequate wet and snow traction for the user, this would be considered an optional practice. It is recommended that a tire shop/dealer with the proper siping equipment sipe the tire to the proper depth and frequency.”

The cost of aftermarket tire siping will vary from region to region, and Nespo points out that if the siping process is done multiple times on the same tire to provide necessary traction it could become expensive.

“At a shop it usually will be about $25 per tire, but that could range depending if they have to pick out rocks and debris from the tread beforehand,” said Cressman.

The initial cost of aftermarket siping may seem relatively cheap but there can be trade-offs in tire integrity.

Altering a product engineered for a specific purpose could lead to compromising the integrity of the product.

“It can offer winter traction but there are trade-offs,” warned Cressman. “If the cuts are too deep it can compromise the tread surface.”

The added sipes also provide a space for rocks to nestle into the rubber and creates more points on the rubber susceptible to chunking and tearing.

The depth, width and distance between sipes are also important. The more pieces there are on a tread, the more it creates a non-solid surface of tire in contact with the road surface and can cause tire squirm.

“You’re creating all new tread elements that are moving all over the place in ways the tread wasn’t designed to move,” said Walenga.

Although siping itself does not negate a tire’s warranty, if a problem arises due to the siping it could negate any warranty coverage.

“There is no hard and fast rule though and some may say it depends on the manufacturer. We take everything case-by-case,” explained Walenga. “If it’s done properly it doesn’t seem to damage the tire but if it’s not done properly it can cause significant problems. It’s kind of tricky because we don’t say do it, but we don’t say don’t do it either.”

In the end, before using any aftermarket tire products, tire manufacturers recommend consulting a tire professional to weigh out all the options.

“A good tire professional will be able to run down a list of other available options that may be available instead of siping. If you get the right tire in the first place you might be able to avoid any requirement for siping,” said Cressman.

“Overall with siping after the fact, I wouldn’t make a blanket statement. There could be benefits but the quality of the work needs to be good and it has to be guaranteed,” concluded Beaveridge. “There are a huge number of professionals, but it only takes one or two to make a bad reputation; check out sources carefully.”

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