IRC Boken Tires: Getting Rolling

IRC Boken Tires: Getting Rolling- by Guitar Ted

The IRC tire company has been around since 1926, but you may not have heard of them unless you were a cyclo crosser or mountain biker in the late 1990’s and early 2000’s. IRC, (Inoue Rubber Corporation) initially started as a bicycle tire company, but became known in the world as a motorcycle tire producer as well as a producer of wheel chair tires. Perhaps their biggest claim to fame, from the perspective of US riders, is the IRC Mythos tires, which were very popular 15-20 years ago. IRC is now making a big push into the US market again with road, mountain bike, and, of course, gravel tires. Look for a big presence from IRC at the “All Things Gravel Expo” at Dirty Kanza this year. IRC also is a sponsor of the Belgian Waffle Ride.

With that said, Grannygear met the good folks of IRC at Sea Otter this year and the result of that relationship is a set of IRC Boken and Boken Plus tires for review here. Let’s take a closer look at these treads.

IRC Boken series tires
IRC Boken series gravel tires.

What It Is: The IRC Boken tire line consists of two 650B models and two 700c models. There is a 650B X 47mm and 42mm offerings, and a 700c X 36mm and 40mm size offerings. IRC also offers the Serac in two different 700c X 32mm sizes and an interesting 700c X 28mm offering in the Marbella. Riding Gravel has the Boken Plus, a 650B X 47mm size, and the Boken 700c X 40mm tire set.

The IRC Boken Plus 650B X 47mm tire
The Boken Plus is the 650B X 47mm tire in the Boken series.

The Boken Plus takes its cue from the “Road Plus” tire category created by WTB. Like WTB’s Road Plus tire, the Boken Plus is listed as a 47mm width tire. The tread of the Boken Plus is somewhere in between the WTB Horizon and the WTB Byway. The center is smooth with flanking file tread strips. then the edges are covered in tightly packed squarish blocks which gain height incrementally as you get closer to the edge of the casing. IRC made the outermost blocks “hollow” for more flex, and thus more grip, when cornering hard.

IRC says the rubber compound is “Ultra-gummy” for the best cornering characteristics. The casing is tubeless ready and is 60 TPI. IRC claims a weight for the 650B X 47mm tires at 570 grams each. MSRP on the tire is $69.99 each. Now moving on we will take a look at the Boken 700c X 40mm offering.

The 700c X 40mm Boken gravel tire from IRC
The 700c X 40mm IRC Boken gravel tire.

This tire has a slightly different tread pattern dominated by small pyramid style knobs across the majority of the casing and flanked on the sides by small, lower profile rectangular blocks. The pyramid type blocks are a bit lower than the very similar Challenge Gravel Grinder and the side blocks are smaller on the Boken than they are on the Challenge tire. The same technical features apply here as with the Boken Plus as far as TPI, rubber compound, and the tubeless ready features. The Boken has the distinction of being the “Official Tire of the Belgium Waffle Ride“, by the way. So…….there is that.

The Boken in the 700 X 40mm size is listed at 420 grams by IRC and has a retail price of $69.99.

Despite being described as tires designed for “extreme” gravel riding, neither Boken variant has a puncture protection belt, or at least none is advertised.

The IRC Boken mounted up.
the Boken mounted up. These tires mount very easily as tubeless tires.

First Impressions: The IRC tires have what is called an “Ultra-gummy” compound and they do have a tacky feel in the hand compared to other tires I have tested. The casings feel pretty standard for thickness as far as tubeless tires go. With no advertised puncture protection belts, I expect a softer ride feel.

The tubeless set up for both the Boken and Boken Plus was dead simple. They go on with some effort, but you shouldn’t need tools. I was able to pump them up, sans sealant, and set the beads with a poor 15 year old floor pump. The Boken Plus went on a set of 650B Easton EA70 AX wheels while the Boken tires went on a set of Irwin Arlo GX wheels. After setting the beads on each rim I deflated the tires and introduced sealant, pumped the tires up to 40psi, and left them sit for 24 hours. After this time period I measured the tires and came up with the following measurements. (Note- I also have added the weights I got from weighing the tires as well)

Boken Plus: Weight- 580/600 grams. Casing Width- 48.8mm

Boken: 480/490 grams. Casing Width- 42.5mm

The Boken Plus tires mounted on the Black Mountain Cycles MCD.
The Black Mountain Cycles MCD mounted with the 650B X 47mm Boken Plus tires.

Well, obviously we have tires well over the claimed weight and width here. In terms of comparisons, the Boken isn’t out of the ordinary for a 40mm tire. The 420 gram figure would have been pretty optimistic. The Boken Plus compares with the Byway from WTB which is around the 540-ish gram mark, so a bit heavier, but the Boken Plus is wider than a Byway, and may stretch a bit more yet. At any rate, these IRC tires are definitely heavier and wider than listed, but this is a sample of one, and your results may vary.

Initial test rides showed that both tires have a more supple ride than not, with the Boken Plus having the expected faster roll. The Boken seemed to be good at shedding the mud I rode through, while the Boken Plus seemed to cling to the same mud. Weird. The Boken showed its “Ultra gummy” compound by tossing sand and small stones more than most tires do. This may wear away as the test goes on, so I will try to make note of this.

The Boken 40mm tires on the Raleigh Tamland Two.
The Boken 40mm tires actually ended up being almost 43mm wide.

So Far…… The Boken tire models are nicely constructed, feel tacky with their claimed stickier rubber compounds, and turned up to be both heavier and wider than advertised. With no puncture protection belts, we expect a smooth ride. Tubeless performance was very good. The initial test rides show promise, so stay tuned as we go forward to the “Checkpoint” part of the review where I will break the review into two parts to feature each tire separately. Stay tuned…….

Note- IRC Tire sent over the Boken Plus and Boken tires at no charge to for test and review. We were not paid, nor bribed, for this review and we will strive to give our honest thoughts and opinions throughout.


Author: Guitar Ted

Guitar Ted hails from Iowa. Home of over 70,000 miles of gravel and back roads. An inaugural member of the Gravel Cycling Hall of Fame and Co-creator of Trans Iowa in late 2004- Guitar Ted has been at the forefront of the growth of gravel events and riding since then. Creator of Gravel Grinder News in 2008, he produced the premier calendar of gravel and back road events. GT joined forces with Riding Gravel in late 2014.

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