Video: Understanding Blackborow

Pete Koski takes you through the details of the Blackborow fatbike design in this short video.

For more information on Blackborow, our five-inch tire platform fatbike, click here.

This post filed under topics: Blackborow Fatbike Kid Pete Koski Video

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ABOUT THE AUTHOR

Mike Riemer

I love being outside. I prefer to ride on dirt. Or snow. If I was born a hundred years earlier I might have been a polar explorer. There's a great natural world out there to see, smell, taste, listen to, and experience. Life slows down out there and the distractions we've created will disappear if you let them. Give me a backpack and let me go.

COMMENTS (11)

Erik | November 13th, 2014

Any updates on shipping of the DS? I though I remember reading early December…

Christopher Tassava | November 16th, 2014

Love this bike. I was lucky to ride a loaner DS for a couple weeks, and I found the machine to be well designed and super fun to ride. It’d be the perfect complement to my Mukluk and Vaya.

How, though, did Koski bend the rim of his gray trucker? Mine is apparently reinforced with titanium.

Matt | November 20th, 2014

Will the Bearpaw thru axle fork be available for aftermarket?

Andy Palmer | November 21st, 2014

Hey Matt,

Yes! In fact, it’s in stock at our distributor right now! The part number is FK8251 with an MSRP of $449 It has a 483 Axle to Crown, with a 51mm offset and an included Thru-Axle. Our aftermarket color is gloss black like our our other forks.

Get in touch with your Salsa dealer to get your hands on one. We will be adding it to the Salsa site very soon, so keep an eye out. Have a good one!

-AP

Matt | November 21st, 2014

Thanks Andy!  Looking to convert my Mukluk so I have the ability to flip flop between rigid and Bluto.  What color does it come in?  Black I assume?

L.E.D. | November 22nd, 2014

Is it possible to fit any other cranks and bottombrackets on the Blackborrow?
Or do i have to buy a Surly OD crank and BB if i buy a framekit?

PK | November 24th, 2014

L.E.D. - Yes, you can run any of the RaceFace Cinch cranks on the Blackborow as long as it is the longer “190 spindle” version.  Proper install per RaceFace calls for 2 x 1.5mm spacers on the drive-side between the bearing seal and crank arm, and 1 x 11.5mm spacer on the left side.  The largest direct mount 1x ring fit-able is 30T per digital data (I have not had a chance to physically confirm this though).  Keep in mind the Q-Factor is ~222mm compared the to O.D.‘s ~213mm.  The O.D. was specifically designed to minimize Q-factor on both 170 and 190 Fatbikes by setting the rings where they needed to be and then shaping the arms as narrow as possible (while still maintaining the use of an FD.)  Bang-for-the-buck, the Surly OD gets you a ~10mm narrower Q-factor and spindle length than most standard MTB crank designs that are widened for fatbike use.

Tim | December 22nd, 2014

Questions for Pete; Why isn’t Salsa building 190mm frames with narrower BB’s? I am seeing frames (Borealis comes to mind) that have 100 mm BB, and 190mm rear spacing. The width of the frame at the BB keeps growing on these bikes, and I much prefer the feeling of a narrower Q. I am guessing that Salsa/Surly increased width to increase stiffness at the BB, but is this really necessary? Is the increased BB width a solution to heel strikes?

PK | December 29th, 2014

Tim,

BB shell width does not correlate directly to q-factor. Spindle length determines q-factor.  There are several ways to take up the spindle length with various combinations of BB shell types and bearing styles.  For example a SRAM XX1 fatbike crank (q=202mm) can be fitted to a Mukluk with a 100mm wide threaded BB shell and also to Beargrease with a 121mm wide pressfit 41 shell.  In either case, the same spindle length is used, and an identical q-factor is achieved on both bikes even though the Beargrease BB shell width “reads” bigger.
The same thing applies to the Blackborow, but around the “Moonlander” version of the Surly O.D. crank.  This crank has a 213mm q-factor and can be fitted to either a 100mm shell using “super cups” (extra wide bearings & outboard cups, or a 132mm wide pressfit shell.  Either way, the spindle length and q-factor are identical.
We did not and never will design a fatbike that features both 190/197 rear spacing and compatability for 5” tires, around any crank with a ~67mm chainline.  Cranks like the X5/X9/XX1 offerings from SRAM are designed for 170/177 fatbikes and ~4” tires (often referred to as 100mm cranks). This fact alone is why they have narrower q-factors.  Pairing a ~67mm chainline crank and 190/197 rear hub (like is found on Blackborow) skews chainline and degrades shifting performance as well as drivetrain life.  This combo is not endorsed by SRAM.  Since we have enjoyed working with and advising SRAM in the past on projects like their fatbike cranks and also the Bluto, we are going to stick with what they recommend on this one.  If you want to read up further on the subject of fatbike drivetrains and rear hub spacing, check out this past blog entry.

http://salsacycles.com/culture/tech_talk_understanding_drivetrain_rear_tire_capacity

Lastly, we chose to design Blackborow around the Surly O.D. crank because of the (limited) OEM choices at the time for ~76mm chainline.  Of them, the Surly crank offers the narrowest q-factor (213mm) at the correct ~76mm chainline and is still 2x compatible.  There are other option like the “190-spindle” RaceFace face cranks, but these arms are standard MTB cranks stretched out and result in a 222mm q-factor.  The RaceFace Next SL is by far the best option for 5” tire compatibility with the narrowest q-factor, but there are 3 draw backs:
  *1. It is limited to 1x only (not an option for us for the Blackborow design/user experience).
  *2. Extremely expensive for OEM spec on a complete bike.
  *3. Due to the narrow q-factor, the width between the inside of arms makes designing a C/S tube in metal that is both stiff, strong, and light extremely difficult.
I’m not bad-mouthing RaceFace, the Next SL is the jam, but not a crank we can spec on a complete bike at the price points the Blackborow is targeted at.
Using a 132mm shell in favor of 100mm shell allows the C/S tube wider target to aim for as they pass by the tire.  This results in a softer bend, and shallower dent, both which allow us to use a thinner tube and also results in a stiffer & stronger truss than if we bent them to hit a 100mm wide shell and dented them to maintain 4.8 tire clearance.  Hope this answers your question.

Tim | December 29th, 2014

Pete, thanks for a most comprehensive explanation!

Slim | November 6th, 2015

Regarding crank width:
Are any of the SRAM cranksets long enough in the spindle to fit in the bottom racket and clear the frame?
When using a different offset chainring/spider (eg Boost or short spindle) it’s probably possible to achieve roughly a correct chain line.

Same question for the Raceface cranks, Aeffect and Turbine Cinch and Next SL. Raceface lists a 75mm chain line on their ‘170 rear’ spindle cranks if you ‘flip’ the direct mount ring, so the chainline should be good.
Will the spindle clear the bottom bracket and will the arms clear the frame?

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