Tire siping is a process in which thousands of razor-thin slits are cut into a tire tread. New tires often include sipes in their design, but some tire dealers also offer to put these slices in customers’ tires on demand.
Why? The answer is simple: because siping can improve a tire’s traction in snow and ice, giving all-season tires the bite of severe snow-service tires and allowing high-performance tires to go from free-spinning to the level of all-season tires. Siping is especially popular in snowy regions where consumers may choose this option as a much less costly alternative to buying a new set of snow or winter tires for their vehicles.
Siping increases the number of edges that a tire has to bite into snow. Tests conducted by the National Safety Council showed a 64% increase in breakaway traction and an increase of 28% spinning traction on ice with siped tires compared to unsiped tires. In stopping distance tests, the reduction was from 200 feet to 155.6 feet – a 22% improvement, according to the study.
While opponents admit siping enhances traction on snow and ice, they note the process makes the tread squirm more, decreasing performance on dry pavement and increasing wear. By making the tread more flexible, siping increases rolling resistance, thus reducing gas mileage. It also results in more road noise.
Opponents argue that actual winter tires designed to stay flexible at low temperatures are better than siped all-seasons.
A professional, shop-grade siping machine designed for passenger car and light truck tires costs over $5,000 and requires factory training, included with delivery. Could siping be a profit center for your shop? Maybe, if you live in the Snow Belt.
One siping machine manufacturer says the process takes only 3 to 4 minutes per tire to perform. Nearly any type of tire can be siped – new, retreaded or used – as long as the tire has at least 5/32nds of tread left.
Available adapters allow the company’s machines to fit mounted tire/wheel assemblies from 12 to 24.5 inches in diameter.
Another of the maker’s siping machines includes 12 cutting blades, along with four lead screws for siping depths of 5/32nds, 7/32nds, 9/32nds and 11/32nds; a file; and a wrench for switching lead screws.
Not all tires can be siped, but a consumer with aggressive mud tires advocates getting them siped for added winter ice traction. On an Internet forum, he wrote, “If your tire can be siped, try it. You’ll probably like it, and if not, it’s not a very expensive lesson to learn.”