The WTB Cross Boss looks to be the new boss in town. We saw the physical tire at Bike PressCamp this summer, and it looked like everything we had been waiting for: a high-volume tubeless tire with a versatile tread. Measuring a true 35mm when mounted on a 23mm OD x 19mm ID rim, the Cross Boss seeks a larger niche than the top-level racers limited by UCI regulations.
The tire’s knobs are set 5mm narrower than the rounded casing profile; this means that the 2mm-tall square knobs (which rise to 2.5mm for the most peripheral row) touch the ground. The Cross Boss weighs 400 grams with WTB’s TCS-tubeless compatible system, which follows international standards for a sealant-based tubeless system. These were the same designs incorporated into the already-proven Cross Wolf that WTB introduced last year.
The bead has a slightly squared profile and fits tightly, one indication that this would be a reliable tubeless tire on wide variety of rims. This is one of the few cyclocross tires that we’re able to fit and run reliably on a non-tubeless rim without the use of a rim strip. However, that tight bead also makes this tire very difficult to mount on some rims, and may require a day of stretching with a tube installed before you can mount it tubeless on your desired wheels, and a bead lubricant (such as soapy water) is a must.
The tread pattern is tight over the center of the round casing, but the spacing widens with the peripheral row. In use, this pattern provides superb grip on almost every surface it rode it on: pavement, hard pack, loose pack, sand, grass, loam.
The peripheral knobs are just slightly taller, and they dig in a bit when leaning the bike, but they did not feel squirmy on pavement at all. The knob positioning places all the knobs in contact with the ground when the tire is in an upright position. When leaned, the slightly taller peripheral knobs dig in deeper. From my testing, only at the most extreme lean angles will you “run out of knob,” a position where no knob would really hook up, putting you on the ground regardless.
This is definitely not the ideal sticky-mud tire, nor the best in slippery mud, either, but the 2mm-tall knobs do reasonably well in the slightly looser muck you might find in coastal regions. It’s a combination of knob height with just enough spacing on a wide tire that makes the Cross Boss stand out above others with a similar tread pattern.
The supple TCS casing not only keeps the tire light for its size, but when run tubeless, the ride is tubular-smooth, offers great floatation, and thanks to the wide conforming quality, offers great grip. Most cyclocross riders and racers are not UCI-constrained to the 33mm maximum width. The 2mm more width fits easily into almost any ’cross bike frame and offers improved versatility, traction, floatation, cornering and comfort. It is an immediately noticeable improvement in all these areas—with minimal weight increase: you can ride your bike faster and more aggressively than with the same tread pattern of a smaller width.
Given the excellent parameters of the bead fit, almost every rider can benefit from this on their cyclocross bike, though if you do not have tubeless-compatible wheels, you may want to use a rim strip—even if we got by without it.
Even if you use this as a standard clincher tire with tubes, you will still benefit from the increased volume and excellent tread. While there are other 35mm tires out there that will work as tubeless, this is the first that is designed as tubeless and is proving to be reliable while remaining supple and relatively light with a versatile tread. In a short time, this has become one of my favorite cyclocross tubeless tires.
WTB Cross Boss TCS Tubeless Cyclocross Tire Specs:
Width: 35c labeled (with a narrower tread width)
More info: wtb.com