Product info
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Weight: 33 grams
MSRP: $2
For model year 2015 we are proud to add the Blackborow to our fatbike lineup. Blackborow is our plus-size tire fatbike. Designed specifically for five-inch tires mounted on 100mm rims, Blackborow maximizes flotation without sacrificing fantastic handling characteristics. Beaches, dunes, blazing trail in a fresh snow fall, or bushwhacking from point A to point B; Blackborow's combination of flotation, traction and handling makes riding across extremely soft surfaces possible.
2015 Blackborow 1...
Blackborow benefits from our experience with its older and slightly skinnier siblings; Mukluk and Beargrease. Blackborow takes an approach similar to Beargrease; a super-short 440mm rear center paired to longer front center, thanks to a 51mm offset fork. This allows for Blackborow to have snappy, mountain bike-like handling characteristics, while still maintaining an overall stable wheelbase. This also puts the rider's weight in an optimal position between the front and rear wheels without needing to make the front end artificially tall.
Like the Mukluk, Blackborow features our super-versatile Alternator dropouts, which allow the chainstay to be lengthened to as much as 457mm for extra stability when loaded down with racks and bags for deep backcountry expeditions. The head tube angle is set to 69.5 degrees, which combined with the 51mm offset, maintains the steering feel to our other fatbike models despite the addition of the much larger five-inch tire and wider rims.
The bottom bracket height of Blackborow is slightly higher than both the Mukluk and Beargrease. This increases ground clearance and reduces pedal strikes, perfect for riding over logs and rocks, through deep snow, or in a trough of a rutted-out jeep road. Larger diameter tires and a higher BB height would typically raise standover height, so we lengthened the seat tube by an inch per size, then dropped the toptube drastically and added a jump brace. This actually results in Blackborow having the lowest standover of all of our fatbike models; another great attribute for a bike you intend to ride in places where riding might actually be difficult. Dabbing and dismount/remount are easier on the Blackborow.
At the heart of the Blackborow model is a heat-treated alloy frame made from 6066 tubing. This top-shelf grade of aluminum offers higher yield strength and fatigue properties than 7000-series and 6061 tubing, which allows us to build a very light and strong frame. Aluminum is also very corrosion resistant, which makes it a great choice for a fatbike like Blackborow and the conditions it will likely be ridden in (or hauled through). Mechanically formed triple- and double-butted tubing is used throughout the frame. These specifically engineered internal thickness changes and external shaping combine to create a frame that is strong in the areas needed and stiff in the directions that matter.
An offset 132mm wide PF41 BB shell creates a lot of welding space for the chainstays, which allows them to have more relaxed bending and tire clearance dimpling as they pass around the massive tire. When compared to a chainstay that is heavily dimpled and bent to pass around the same size tire to a 100mm wide BB shell, the straighter Blackborow chainstays are stronger and can be made using thinner tubing (for weight savings), while also yielding a more laterally stiff frame that is less prone to fatigue failure though the heavily manipulated area.
The BB shell and chainstay are matched to a 12 x 197mm thru-axle set of Alternator dropouts. This creates a tire cavity in the frame with clearance for five-inch fat tires mounted on 100mm rims while also properly aligning the drivetrain for optimum shifting performance and no chain rub with either 1x or 2x setups. The 132mm offset PF41 BB shell is designed to fit Surly's OD Moonlander crankset, the only production crankset with a 76mm chainline that uses fully outboard bearing positions on the crank spindle. This bearing placement creates the best loading scenario for the bearings and spindle, which means longer bearing life. 197mm thru-axle spacing at the rear dropouts is used in favor of a 190mm quick-release due to the stiffer and more secure wheel connection the 12mm axle offers compared to an ultra-long 5mm diameter QR rod.
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