In addition to big wheel tire design, Mark was also instrumental in frame design of the early 29ers. WTB brought a 29" wheel bike to Interbike in October of 1999. Mark showed me that bike and Wes Williams also showed me his bike. I was instantly intrigued. After the show, Mark shared the frame drawings with me to help me create my first 29" wheel frame design - a 4" travel full suspension bike that never saw production. There were only two frames made - one I gave back to Haro (wish I still had it) and one I gave to Mark. A few years after that, I was able to get the green light on a couple of production bikes, the Mary SS and Mary XC, which I heavily borrowed design cues from WTB's Phoenix frame.
So, fast forward several years and with almost a decade of 29" wheel design under his belt, Mark has created a bike that draws on all of his experience - the OS Bikes Blackbuck. The frame is a clean, simple design. The curved seat stays harken back to the days of the klunker, take the edge off bumps and open the seat stay/chain stay junction so the disc caliper can be mounted within the triangle cleaning up the look of the bike.
Other frame design bits include:
Three downtube bottle bosses so you can run your cage low or high, or run one of the old WTB designed/Blackburn produced bottle cages for 1.5 liter bottles.
Large contact area where the seat stays joint the seat tube/top tube.
Head tube with extra thick wall at the bottom to resist ovalization and to add strength to counter the long lever of the 29er suspension fork.
Down tube gusset formed to add strength and provide clearance for the suspension fork's knobs.
Eccentric bottom bracket secured with a unique split shell design.
The boss on the down tube is for a bolt-on cable stop if you want to run a front derailleur. This coupled with the bolt on derailleur hanger that is included with the frame means that, with judicious use of zip-ties, you can run this one speed bike as a fully geared bike or as a 2 or 3 speed bike (a get to the trail gear, a trail gear, and an O-M-G, I need a bail-out gear).
The frame is available as a frame only that can be built up to your heart's desire or a complete bike. The complete bike specifications are:
Fork: RockShox Reba SL 80mm
Crankset: Truvativ Stylo 175mm
Wheelset: WTB LaserDisc rims, LaserDisc Single Duty hubs, WTB spokes, all shod with 2.1 Nanoraptors
Brakeset: Avid Juicy 7 hydraulic disc with 160 rotor in back and 185 rotor up front
Headset is an FSA Intellaset
Seat: WTB Deva.
Bar/Stem/Seat Post: Non-branded Kalloy. Good stuff, no frills. Seat post is 27.2 x 400mm.
Frame sizes: One frame size. If you are between about 5'10" and 6'3" tall, with a maximum 36" inseam, having only one size is no problem at all!
Geometry is (with 80mm Reba):
Head and seat angle: 71.3 degrees
Seat tube length: 19" with EBB at it's lowest position
Maximum seat height (center of BB at it's lowest position): about 32"
Effective top tube: 24 5/8"
Chainstay length: 17 3/8" (with ebb at about 11:30)
Head tube length: 4 1/4"
BB height: 12 5/8" (with EBB at about 11:30)
How does it ride/handle? Technically, my seat height is about 1 1/2" taller than the tallest with the stock seat post, so I can't really get out there and put it through its paces. However, the little time I did spend on it showed that the bike is a very capable handling bike. It is very neutral. The best thing you can say about a bike's handling when asked is "nothing." When the handling of a bike is such that you don't even think about it, that's when a bike is dialed. I also liked the chainstay length. For us tall guys, it keeps the wheel under our butts and the front end on the ground when climbing.
But the best thing about the bike is it's really cool looking. The silver paint in the rear with the red pinstriping is classy. The lack of a big billboard name on the down tube is refreshing and the simple Blackbuck on the seat tube and OS on the headtube accentuate the cleanliness of the bike's design.
All this does come at a price, though. Although, there is, for what you get, a lot of value in it at $1750 for the complete bike and $500 for the frame.
Some more photos