Tires? Yes.

What tires to run for the Black Hills BackBone?  That's like asking what type and set up of bike to ride.  Everyone has an opinion, maybe because many types and sizes of tires will work just fine.  At gravel races, I've seen everything from 28 mm road tires to 4+ inch fat bike tires.  Like your bike.  Run what 'cha brung.  And have fun.

That being said, I've ridden these roads every which way under a variety of conditions, with four very different types of tires that fit my Black Mountain Cycles cross bike:  30 mm road slicks, 35 mm cyclocross knobbies, 38 mm light touring road tires and 43 mm 'tweener knobbies.  One could make a case for each of them for the BackBone.  As between these four types of tires, here's my take.

With loads of clearance, my Black Mountain Cycles monster cross bike allows many tire options. 

Start with the road surface.  The Northern prairie portion of the route is generally pretty hard packed, lightly graveled but sharp.  Sidewall cuts are a real possibility.  As Spearfish approaches, the gravel gets thicker, less sharp, and generally more like MidWestern gravel.  Into the Black Hills, the gravel again thins out and, while generally very nice to ride, the surface can be soft, rutted and strewn with debris.  Onto the Southern prairie, the gravel is again more like MidWestern gravel that gradually thins to near dirt at the Nebraska border.  See prior post Not Your Grandpa Joe's Gravel.

My go-to tire for the BackBone, and generally for this type of riding, is a 38 mm road tire, which currently is the Schwalbe Marathon Racer, a touring road tire lightest in the Marathon line. The relatively fat (for a road tire) profile and low pressure make for a comfortable ride, despite the substantial sidewalls and internal flat protection.  By the way, that flat protection works.  I have had only one flat in over 5,000 miles of rough roads on those tires.  At 38 mm, it's also wide enough for control at speed over those surfaces, without being too sluggish, heavy or buzzy.  I have not felt the need for bigger tread on any of the rough roads I ride, including the BackBone, the Almanzo Royal, the Gold Rush Mother Lode and Odin's Revenge (twice).  It's the sweet spot for me.

These Marathon Racers need to retire, but I keep putting them back on
after the planned replacement tire just doesn't do it as well.

Others may prefer a tire with more meat.  Before trying the Marathon Racers, I rode a full season on a knobby cyclocross tire with a subtle centerline tread, the 35 mm Schwalbe Smart Sam.  For all those knobs, it rolls pretty well.  I enjoyed many gravel and dirt miles in the Black Hills, as well as races like the Gold Rush, Odin's Revenge and Gravel Worlds.  Although the knobs were handy in spots, it seemed overkill for most of the miles on any given ride.  So, rather than moving to a semi-slick cyclocross tire with fewer knobs, I decided to try a wide, smooth road tire, which led me to the Marathon Racers.  The Smart Sams were quickly relegated back to cyclocross, for which they were designed.

Schwalbe 35mm Smart Sam cyclocross tires work well enough.  They're just better at cyclocross.

To push the road tire concept a bit further, I also tried the Schwalbe Kojak, a no-tread, slick tire with internal flat protection akin to the Marathon Racer.  These may have worked out, if they actually were the 35 mm width as advertised.  Instead, mounted and inflated, they measured but 30 mm, which I found to be too skinny for the roads I like to ride.  I did not get any pinch flats, but the overall ride was much less comfortable and less stable in rough conditions, especially at speed.  I didn't keep them on my bike long enough to take a picture, but I will keep them for pavement-only rides, where they should shine.

At the other extreme, I also tried 43 mm Bruce Gordon Rock 'n Roads, a 'tweener tire with beefy tread providing loads of traction on loose stuff.  These would work on many single track trails.  I've ridden the Rock 'n Roads for about 500 miles, including this year's 127 mile Omaha Jackrabbit, which featured over 25 miles of rough dirt, minimum maintenance roads.  But the substantial tread is just too much for me and the road buzz is a constant reminder of the drag.  More importantly, I keep getting flats on these tires, no matter where or how I ride them.  Not fun.  I don't plan to rely on the Rock 'n Roads for any future, significant ride, unless converted to tubeless and tested thoroughly.  Even then, I question their durability.  Just not for me.

43 mm Rock 'n Roads cruised the dirt roads at the Omaha Jackrabbit.
I was amazed that I had no flats over 127 miles.  That's a record for those tires.

There are a growing number and variety of tires entering the market targeted for gravel and dirt road rides.  For example, Schwalbe announced a new tubeless tire for this purpose, the G-One, available next spring.  I'll certainly take a pair of those, in 38 mm.  And if those don't pan out, I'm sure I'll eventually find something better than my current touring tire pressed into gravel duty.

Schwalbe G-One.  Next up.  Next spring.  That's a lot of knobs for me.  We'll see.

In the meantime, I'll stick with my tried and true 38 mm Marathon Racers.  On all roads.  In all conditions.  Time to ride.