Mavic's Crossmax tires have a harder rubber in the center of the tread, but softer side knobs (click to enlarge).

Mavic's Crossmax tires have a harder rubber in the center of the tread, but softer side knobs (click to enlarge).​

Editor's Note: This article was written by Art's Cyclery web content editor Brett Murphy, who uses his mechanical engineering background to explain the latest industry advances and breakdown component design. The original post can be found here.

Most riders spend considerable time selecting a saddle or grips, prioritizing their contact points with the bike. But often the most important contact point - tires - is overlooked.

Tires are your contact point with the ground and make a significant difference in your bike's handling performance. It can, however, be hard to choose a tire if you don't understand construction methods, rubber compounds, and rating systems.

Indeed, tires can seem very abstract, leading consumers to choose based on price and looks. But after you learn some basic tips and terminology, you'll feel more confidant when making tire buying decisions.

Important factors include tread patterns and combinations based on terrain and intended use, and construction methods of the tire rubber, bead, and casing, which are the focus of this article.

Basic tire construction. Photo courtesy of Maxxis Tires/Art's Cyclery

Basic tire construction (click to enlarge). Photo courtesy of Maxxis Tires/Art's Cyclery​

Tire Beads

The tire bead hooks underneath the edge of the rim hook. Tubular road tires don't have a bead, but all other tires have wire Kevlar (foldable) or carbon beads. Bead profiles will vary depending on intended use. UST (universal standard tubeless) beads have a squared off profile with a small flap on the edge to facilitate easy initial mounting and an airtight seal. These beads are designed to hold air without sealant.

Casings

Casings run from bead to bead and are rated in TPI (threads per inch). The casing is essentially a fabric that acts as a skeleton underneath the tire's rubber. Higher thread count casings feel more supple and improve ride quality. Higher TPI tire casings, while providing excellent ride quality, are more fragile and not desirable for applications where the tire needs to stand up to a lot of abuse on rough trails or roads.

Compounds

Tire compounds will most likely make the biggest difference in the feel of your ride compared to a casing's TPI. Rubber compounds are rated using a Shore hardness durometer, the durometer being a device used to measure the hardness of rubbers and other similar materials. There are more than 10 different durometer scales denoted by a letter following the rating. This rating is out of 100 and is a measure of the amount of deformation of the object. So if a tire exhibited absolutely no deformation, the Shore Durometer rating would be 100A. In comparison, most tires measure at about half of that. Soft compounds provide better performance while descending due to their grippy nature, but will wear much faster. Hard compounds offer lower rolling resistance and longer lasting tread life.

Continue to page 2 to learn more about selecting tire compounds »

Schwalbe is one of several manufacturers that uses a triple compound set-up where a harder base layer is placed beneath softer compounds.

Schwalbe is one of several manufacturers that uses a triple compound set-up where a harder base layer is placed beneath softer compounds (click to enlarge).​

Dual (and Triple) Compounds

Many tires are composed of one rubber with a single hardness rating, but higher quality tires combine multiple rubber compounds for more desirable performance across a spectrum of riding conditions.

The Mavic Crossmax Roam XL is a great example of this. It has harder rubber in the center of the tread, measuring 60A on the durometer scale, but softer side knobs measuring 50A. The 60A rubber is harder and better for faster rolling over fire roads as well as long term durability. The softer shoulder compound grips the trail better and allows for more traction while cornering.

Some brands such as Maxxis and Schwalbe even offer triple compound tires that layer multiple compounds with a harder base layer beneath softer compounds. This results in longer lasting tires that grip better than a single compound tire with a similar tread life.

Schwalbe TrailStar Triple Compound. Photo courtesy of Art's Cyclery

Schwalbe TrailStar Triple Compound (click to enlarge). Photo courtesy of Art's Cyclery​

Putting It All Together

Taking all of this into consideration, you can now better weigh the features of potential tires to best select one that will work for you. Cross-country riders will likely select high TPI tires with a higher durometer for decreased rolling resistance, while the opposite will be true for people who lean toward more aggressive riding. Just remember that while high TPI provides suppleness, it's also important to look for a more durable tire with a lower TPI and possibly some added layers of casing protection.