Tires proved the most surprising story of the Outside magazine bike test this year in Tucson, Arizona. In two weeks of testing 50 bikes, with a dozen riders on each bike every day, we had only two flats. To put that in perspective, at the 2017 test, we flatted 18 times, and in 2016 we tallied a whopping 27. Previous tests had at least that many flats, and often more. From the nasty, barbed plant life to the serrated rocks that litter the roads and trails, everything in Tucson is out to shred your tires, which makes our dearth of flats even more impressive.
Because the results stretch across wheel and tire size, bike type, tire and wheel combos, and even brand, the inevitable conclusion is that tire designs as a whole are improving. Even beyond the bike test, I’ve had so few flats on my year-round test fleet that I can hardly remember the last time I changed a tire.
So how do you explain these improvements? “We are finally a few years into tubeless tire development, and we are hitting our stride,” says Clayton Wangbichler, a spokesperson for WTB. “Early on, companies were adapting tube-type tires for tubeless, and it was a learning curve to find out what worked and what didn’t. We’ve moved beyond those days and we are fine-tuning tires with different plies, better casings, and a variety of compounds to suit conditions. Also, rim designs are now built to facilitate tubeless setups.”
Probably the biggest factor contributing to improved durability and feel is sidewall and tread protection, which amounts to some sort of protective layer built into a ply of the tire. “I think we have finally figured what materials work,” says Graham Wilhelm, product manager for Trek’s wheelworks program. “We know specifically what type of nylon, what TPI of nylon, and what weave of nylon works best.” And it varies from tire to tire. For trail and all-mountain designs, for instance, Bontrager uses three sheets of 40TPI nylon, one in each sidewall and one sub-tread. On cross-country tires, there are only two sheets of 60TPI nylon in the sidewalls. “I think you see this across the board: companies have really focused in on what works, so you’re getting tires today that weigh the same as they did five years ago, but they are so much more durable.” Wilhelm also points out that improvements in tread design mean better control, so riders are less likely to flat because they’re riding better lines.
Aaron Chamberlain, at Maxxis, whose tires graced over half the mountain bikes we tried, says they have new technologies as well, including DoubleDown, which uses two plies of casing, like a downhill tire, but with lighter 120TPI casings for better feel. “Bikes are capable and more aggressive, so we have to keep up with that,” he says. He also credits the trend toward wider rims for some of the added durability in tires. “More bikes are coming stock with wider rims. That allows the tire to spread, which reduces the risk of pinch flats.” That echoes the approach Enve took to taming flats when it redesigned its mountain series wheels last fall.
Manufacturers also seem more concerned with durability than weight. “When tubeless came out, it was all about weight, but we’ve come to realize that you can’t always cut weight at the expense of reliability,” says Wangbichler. Whereas a decade ago I strived for lightweight mountain race tires that weighed in the 400-gram range, for instance, these days 500 to 600 grams is more realistic, partly thanks to those thicker casings and wider profiles. You can argue over how much an extra 100 grams slows you down, but there’s no debating that you’ll be a lot slower if you flat thanks to tires that are too lightweight.
Bike companies seem to have gotten this message, too. A few seasons ago, most brands were spec’ing the skinniest, lightest, cheapest version of tires so that their bikes would feel as feathery as possible on the showroom floor. At our tests, we’d shred that paper-thin rubber immediately. So it’s heartening to see that more companies are spec’ing heavier weight tires with additional sidewall protection. Specialized, for instance, includes its GRID tires, which have reinforced sidewalls, on all models of its trail bikes, starting with the Stumpjumper and up. And pretty much every bike in the test that came with Maxxis treads included the company’s burliest 3C/EXO/TR designation for the best tear and puncture resistance. “A lot of manufacturers have realized that spec’ing the lightest tire possible means customers are going to be flatting all the time,” says Chamberlain. “And that just makes everyone look bad.”
Tires are getting wider across the board, too. Most of the road bikes we tested were equipped with 28c tires and many had up to 32c—that’s a far cry from yesteryear’s 23c standards. And whereas 2.1-inch tires and smaller were the norm on cross-country race bikes not long ago, this year the BMC Agonist came with 2.25s, and the Specialized Epic got a 2.3. Increased volume doesn’t necessarily mean better durability, especially since pressures generally drop as sizes go up, but it does translate into a better ride. “I think you can trace it all back to fat bikes,” says Sean Estes, at Specialized. “Riders immediately loved the confidence, the added traction, and the fewer flat tires. You get an incredible ride quality with bigger rubber. The trade-off is weight and rolling resistance, so now the push is to find the sweet spot that balances all the factors.”
Enter the 2.6-inch mountain tire, which was probably the hottest item on deck this year. Six bikes came spec’d with this new size, and I imagine that even more would have except that early run availability has been tight. Splitting the difference between 2.4s, once considered a big mountain bike tire, and 3.0s, the original standard for plus bikes, this size provides tons of traction and push through loose terrain and chunder but doesn’t have the same lethargic sensation you sometimes get with plus. “I think it’s sort of a backlash to plus,” says Chamberlain. “There was all this hype about how plus was going to change your life. It’s good for some things, but can also feel vague and slow. So this is the pendulum swinging back the other direction.”
We had two enduro bikes in the test, the Pivot Mach 6 with a 2.5-inch Maxxis DHF front and the Ibis Mojo HD4 with a 2.6 Maxxis DHF, and hands-down the control and confidence of the bigger rubber won out. As an experiment, I switched the fatter tire onto the Pivot, and I liked that bike even more. The differences were incremental, of course, but noticeable, which probably explains why this size is exploding. “I was surprised to find out that 2.6 is leading our sales right now,” says Trek’s Wilhelm. “For me, it’s definitely the magic middle.”
One last note: If you aren’t carrying a plug kit, such as the DynaPlug Pill, you are missing out. Whereas flats in the past meant installing a tube and losing your tubeless benefits, we fixed both of our flat tires with a quick plug job. And plugs have gotten so good these days that those fixes lasted the remainder of the test—and are still going strong.