Buzz is building around 32” mountain bike wheels and tires. You read that right.
While 32” wheels and tires have existed for years in the unicycle market, and have been used in custom bike applications for tall riders, the debut of a dedicated 32" XC mountain bike tire from Maxxis at March's Taipei Cycle Show likely signals that something is coming soon from major mountain bike brands.
A larger diameter than the current 29” mainstay could offer benefits like enhanced rollover, stability, and traction. Plus, on very large frames, big wheels are more aesthetically pleasing and perform better. Yet there are drawbacks like added weight, slower acceleration, and geometry red flags for average to short-statured riders.
But does the industry need another standard to support? I recently talked to a few brands involved with the rise of 32 to learn more.
Opening a mold, and possibilities
I’m old enough to remember the hype around 29” bikes when they first came to market in a production capacity during the early 2000s and subsequently soared in popularity, eventually overtaking 26” as the optimal wheel size for mountain bikes. I was even the proud owner of a second-generation Surly Karate Monkey and, later, a few early Niner hardtails. At 6’1” (185 cm) tall, the primary draw for me was enhanced traction, better stability from longer wheelbases and rotational inertia, and improved ability to roll over obstacles than previously offered by 26” wheels. At my height, I had few of the initial issues that plagued bike geometries for smaller riders like toe overlap and limited standover.
Creating a new wheel size for bikes is an uphill battle, with tires creating the biggest bottleneck to development. This was the case back when designers tried to gain traction with 29ers and has been happening again in recent years as brands have explored 32” models.
In terms of numerical minutiae, Bead Seat Diameter (BSD) is the figure to watch when comparing various wheel sizes. This measurement is the inner diameter of the rim where the tire bead sits. 26” wheels have a 559 mm BSD and 29” have 622 mm BSD, which is an 11.5% difference. Interestingly, the jump from 29” to 32” (686 mm) is actually a bit less, at 9.3%. And, let’s not confuse 32” wheels with the occasionally whispered 750D gravel size, which have an even different BSD of 660 mm that sits somewhere between 29” and 32”.
Until now, most of the 32” bikes available have been custom built around the Nimbus Nightrider unicycle tire, with tread that’s not well suited to off-road use and which weighs a substantial 2.25 lbs /1,020 g each.
Maxxis, however, recently made a sizable investment in creating the first performance-oriented 32” XC mountain bike tire. According to Mountain Liang, Maxxis' marketing coordinator, the Taiwanese tire manufacturer spent about six months developing a process and having custom machinery built to produce the new 32 x 2.4" Aspen.
“Opening a new mold is quite easy, but the production equipment was another [thing]," Liang told Escape Collective. "Equipment [was] totally different from the current production standard and takes time to adjust. Because of the bigger size, we needed to purchase a new machine for making the pre-cured “green tire” and a bead machine for a bigger bead circle in the semi-finished product.” But now that the machines are in place, Maxxis is proverbially off to the races, and the Aspen is just the start. “Since the big investment of these two machines, we can produce other sizes (width) and patterns," he said. "We’ll expand to more models very soon.”
The new tire, says Trek product developer and longtime former pro Travis Brown, is key for the bikemaker's ability to investigate the benefits (and drawbacks) of the larger wheel size. The research project's roots go back to the data the brand gathered on 29ers, which allowed it to build a performance profile that is easily adaptable to testing other wheel sizes. Where the most recent exploration stalled was test options.
Brown told Escape that “in the last 15-plus years, there have been a few low-quality tires in different diameters. And we've actually done a lot of experimentation with those. But the clear data that we need to move forward with something we couldn't get from those tires. So this new tire that was shown at the Taipei show has given us that opportunity fairly recently. The breakthrough of that tire has given us a lot of vision on where it can go.”
Chris Drewes, global MTB product manager with Trek, expanded on Brown’s point. Trek's 32” bike testing has been "backburnered for the last decade plus," he said (Brown jokes that it's the "longest-running Trek R&D project ever"). But the new tire can finally push the project forward. "In addition to some of the field testing, we're able to do some really controlled laboratory testing that is bike and wheel only," Drewes said. "So we're basically trying to look at a very controlled and objective approach with well documented, organized, and objective data as well.”
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