IRC Gravel Collection

IRC Gravel Collection


IRC Tire is currently not a well known name in America, but they are one of the oldest tire manufacturers in the world. Founded in Japan in 1926, the Inoue Rubber Company bills themselves as “The global two-wheel tire specialists”. IRC has a long history of making off-road tires for both motorcycle and bicycle. In fact, IRC developed some of the first Mountain bike specific bicycle tires in conjunction with Tom Ritchey in the 1980's.

Now IRC has turned their attention and manufacturing expertise to the gravel market. The Pure Gravel test team had the chance to take some of IRC's prototype gravel tires out to Catalina Island to put them through their paces on the island's dry rocky terrain. 


One of the interesting things about gravel is that it is not a one-tire-fits-all sport like road, triathlon, or track. Two riders on the same course may want a very different set of tires. Likewise, the same rider may want to change their tires for two different events. Are you riding a hybrid ride that is 50% road and 50% dirt? Are you riding DG walking paths or rutted rocky fire roads, or single track? Soft or sandy soil? Gravel is so diverse that you need a range of tires to choose from.

IRC has tried to meet this need with their “Gravel Collection”. It is made up of 6 tires in 8 total sizes that cover the spectrum from 700x26b all the way up to 650x47c. 


Formula Pro X-Guard

At the narrow end of the spectrum you have the FORMULA PRO X-GUARD 700x28. This is IRC's high-end tubeless road slick with a layer of bullet proof puncture protection IRC calls X-GUARD. The tire is labeled as a 28, but we measured it at just over 25mm on a rim with a 17mm internal channel. This tire is great for road rides with a little dirt thrown in, or for riders who are competing and are willing to give up grip and comfort for flat-out speed. It is a straight-up road tire, but built durable enough to get you through the dirt.

Shop Formula Pro


Next up is the Marbella Tubeless X-Guard. This is an interesting tire. We didn't know what to make of it when we first saw it. The Marbella is a skinny road tire with an aggressive tread. After riding this tire in the mud, we realized why this tire has a place in the IRC arsenal. This little tire fits in just about any road bike, but the aggressive tread grips like crazy when cornering in loose dirt or riding through mud. If you want (or need) a skinny tire for your bike, but want serious offroad capability, this is a great tire for you. The Marbella is actually a little bit lighter than the Formula Pro, so if you are looking for all-out speed on a mixed course like the BWR, this might be the ONLY tire for you. Like the Formula Pro, The Marbella is labeled as a 28, but measures smaller. Ours came out to 26mm. 

Shop Marbella


The next two tires in the IRC gravel collection are actually re-purposed cyclocross tires. The Serac CX Sand, and Serac CX Edge. Both tires are 700x32c, and  these tires measured out true to size. We know from personal experience that the Serac CX sand is a great tire for hybrid rides like the Belgian Waffle Ride.

The Serac Edge is similar to the Serac Sand only it has side knobs which creates a more capable off-road tire that corners better in dirt and sand.

Shop Serac


Now we get into IRC's “true” gravel tires. The Boken 700x36 and 700x40. The Boken is IRC’s flagship gravel tire with soft rubber, a minimal file tread down the center and side knobs for cornering. We rode the 36 in Catalina. We knew we would be doing a lot of climbing so we decided to save a little weight vs. riding the 40mm version.

Shop Boken

Boken Plus

At the wide end of IRC's gravel collection sit their Boken+. The Boken+ is a 650b tire that comes in both 42mm and 47mm widths. Most of our test group selected the Boken+ for their ride. It has a slick center tread paired With side knobs. We should mention here, that although 650x47 has become a standard size, the 42 should not be overlooked. If you have a bike that was made for 700x40c tires, and will not fit 650x47, it will almost certainly fit the 650x42 Boken+. This tire was made to bring the 650b wheel size to (almost) all gravel bikes. 

Shop Boken Plus


You can tell by just glancing at the tire lineup, that IRC's gravel tire design philosophy is to use a minimal tread with a very soft rubber. The logic is that gravel rides are often mixed surface, and the minimal tread rolls fast on the tarmac, and the soft rubber gives you great grip on any surface. They add side knobs for cornering and traction in deep soft soil. These characteristics make IRC's gravel tires perfectly suited to dry and rocky terrain. 


As we said before, we chose the Boken 36 for this trip because we knew we would be doing a lot of climbing and wanted to shave grams. The Boken 36 was amazing on the tarmac and we were very happy with our choice when we were picking our way up 15% dirt roads, but on the way back down we wished we had more tire under us. The riders that selected the Boken+ raved about its capability on the descents as well as how much grip they had when climbing.  

 Rider Comments

  • I rode the Boken+ 47mm with no problems at all! While riding I experienced no slippage on the Catalina rocky soil. Descending on the rough pavement coming down the hillside I felt 100 percent confident. I also had very little concern about flatting at all. Great tire and very easy to mount to the Boyd tubeless rims.  
  • This tire is amazing whether on gravel or the road! The added volume of the 650b meant I could run psi in the mid twenties, providing a secure and comfortable ride on some extreme surfaces. Point down hill on the road and it rolls and corners unbelievably well!  It’s actually nearly impossible to describe - you have to experience this tire to understand it’s capabilities! 
  • Complete confidence as you shred downhill or just grinding through the gravel. 
  • This wasn’t the first time that I have ridden the Boken as I rode Dirty Kanza with them and made it through that with no issues. The smoother rubber on top of the tire with tread on the side really paired well with the Catalina terrain.
  • It's all about volume baby! The Boken 650x42B gave me plenty of grip and the confidence to SEND IT through loose gravel corners. 


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