We first got word of the Clement BOS tubeless cyclocross tire last year at Sea Otter, and then saw early images of it back in September at Interbike, but now we have our hands on one of the first sets to land.
The Clement BOS tire is named after Boston's Logan International Airport three letter code, in typical Clement cyclocross/gravel tire style (other tires are the LAS, PDX, MSO, USH). The BOS is billed as a mud tire.
Another mud tire? Isn't that what the PDX already is? Adding to the potential name confusion, cyclocross racers living outside of Boston may think of the recent dry, dusty Gloucester conditions of recent years when imagining Boston racing.
Clement's Johs Huseby knows all about Boston's cyclocross conditions, having raced professionally for Independent Fabrication and battled the McCormack brothers, Tim Johnson and Jonathan Page at the height of the Saturn SuperCup. He knows that once the temperatures drop, Boston can be as muddy as anywhere in the country.
While the PDX is an accomplished tire, winning titles and medals at Nationals and Worlds, the thin knobs and very open tread that sheds peanut butter mud well aren't for everyone. The tread can wear very quickly when pavement or hardpack is mixed in with mud. And we've always said that we think it's a better front tire than rear tire when driving traction is at a premium.
The BOS looks to be a mud tire that's more versatile and durable, but a bit less open. Mounted on a rim, the tread reminds us of the original green Michelin Mud on steroids. With the bigger knobs it should last a lot longer for mixed terrain use than Clement's PDX. The BOS also reminds us a bit of the discontinued Specialized Captain that came in a 35c 2Bliss form and won Cyclocross Magazine's Editor's Choice Award. Both tires worked really well in the back, with their chevrons helping with driving traction, and early impressions indicate the BOS does really well out back.
The BOS is a 700 x 33 offering that when mounted on a NEXT 28M rim with an internal width of 23.5mm measured out to 34.27mm in our offices. That's a really wide rim, but the measurement still indicates that the tubeless Clement casing, like the company's non-tubeless clincher offerings, runs truer to listed size than most other manufacturers' undersized offerings. That's really promising for the 99% of retail-paying tubeless tire racers who don't race UCI races and prefer the extra cushion, burp protection and lower rolling resistance a wider tire can offer.
Speaking of casing, Clement does not publicly reveal TPI numbers with its tubeless offerings, but admits to having additional materials (butyl rubber, casing fabric, etc.) for strength and sealant compatibility.
The tire's weight on the Cyclocross Magazine scale is 403 grams, which is about average for a tubeless cyclocross tire. (Keep in mind you'll need to add two or more ounces of sealant, but can avoid a six ounce fat 700c inner tube).
Our initial ride impressions from a dry, relatively tacky singletrack ride at 26 psi (166 lb rider) left us impressed. There was plenty of grip, even during hard braking, and lots of bite in loose conditions—something the PDX never excelled at. We had limited muddy sections, but the tire gripped well in those moments, and we are hopeful for spring rains to test their full capability in driving, braking and shedding mud. After our first few initial rides that included a bit of unintentional skidding, the knobs still look quite new and the tread remains free of mud. Those are all promising impressions, and we're guessing racers saddened by both the Michelin Mud and Specialized Captain 2Bliss tires going away will now have a fine substitute. Those were two of our favorite all-conditions clinchers, and we're hopeful the BOS live up those comparisons. Compared to Clement's non-tubeless offerings, the tubeless BOS, with its bigger knobs and thicker casing, feels quite a bit less supple.
Stay tuned for a full review. We'll mount it up on other rims (Road Tubeless, NoTubes) to give you more comprehensive information and rim compatibility, and have much more experience with tread durability and burp resistance.
As we reported during NAHBS, the tire retails for $75 USD and should be available well before cyclocross season.
More info: clementcycling.com