What Are Sipes On A Tire?

Modern tires may seem like a single piece of uniform rubber, but they consist of many parts. Some — such as the beads, radial cord, inner liner, and belt plies — are behind the curtain, so to speak, but are nevertheless crucial for the strength, rigidity, and quality of the tire.

What we see when looking at a tire are the sidewalls and the tread. The former is the side of the tire from the inner beads to the tread, and it's where you'll find all the letters and numbers related to the size, construction, speed rating, and aspect ratio of the tire. The tread is the part of the tire that touches the ground. Tires have three main tread designs: symmetrical, asymmetrical, and directional.

The common denominator among various tread designs is the sipes. The sipes on a tire are those small cuts, slits, or shallow zigzag patterns on the tread. Named after John F. Sipe, who practically invented siping when he cut slits on the soles of his shoes to mitigate slipping in the 1920s, sipes began appearing in tires by the 1950s to do the same thing. Those sipes work silently in the background, helping to increase traction over low-grip surfaces like snowy, icy, or rain-drenched roads.

It doesn't seem like it, but those sipes are like teeth or claws that grab the road, adding more "biting surfaces" on the tread. They also flex and open as the tires roll forward to trap water or snow, which essentially improves grip by keeping the rubber in contact with the road. Moreover, those seemingly random cuts or slits make the tread more flexible, which aids heat dissipation for longer wear and contributes to a smoother, more comfortable ride.

Sure, tires differ in tread compounds, construction, and tread design. But modern technologies enable tire makers to strategically place sipes in the right places on the tread blocks, using advanced modelling techniques to enhance grip, improve comfort, or make the tires roll more silently.

Sipes have evolved from the traditional horizontal or vertical slits. If you hear a tire has advanced zigzag sipes, it simply means it has Z-shaped or interlocking sipes to improve grip. Meanwhile, some tires have three-dimensional sipes that can open or lock together to evacuate slush or dirt to maximize traction.

Going beyond adding traction and all-season capabilities, the strategic placement of sipes on a particular tire can mitigate hydroplaning, offer better rolling resistance, and help deliver better fuel economy. Name-brand tires are more expensive due to their advanced rubber compounds, stronger construction, and improved tread blocks with generous, deeper sipes, and outperform cheap tires when it comes to wet braking. With all those factors considered, it wouldn't be a stretch to say that sipes play a crucial role in how a tire performs.

New tires come with built-in sipes that were part of the design, engineering, and construction of the rubber. This trend we keep seeing and hearing about on social media, called tire siping, is a different matter. Tire siping is the process of physically adding cuts or slits to the tire in order to aid traction over deep snow or icy conditions.

Aftermarket siping has pros and cons, but the additional $60 or so to add sipes to your rig's set of tires could prove beneficial if you live in an area that sees snow or ice for most of the year. But if not, stay away from aftermarket siping. It might void your tire's warranty, for starters, and it may compromise the construction, performance, and safety of the tire on smooth tarmac. It's also illegal in many states, so keep this in mind before you start adding slits to your otherwise good tires.

The better, safer, and possibly more economical alternative to aftermarket tire siping is to purchase a set of winter tires — snow tires on a front-wheel drive car can outperform an all-wheel drive (AWD) vehicle with all-season tires.