Beautiful Bicycle: Joseph's BMC Fourstroke 01

If you've spent any time around Contender, chances are you know Joseph Bonacci (or JoBo, as he's known around these parts).

A longtime staffer and familiar face to many of our customers, Joseph is our resident tech nerd, as much a student of the sport as he is a dedicated rider across all disciplines, former mountain bike racer, and now all-around bike lover. So when it came time to build his own BMC Fourstroke from the frame up, every choice was deliberate. Nothing was left to chance, and the result is a bike that blends bleeding-edge tech with proven race-day dependability.

The star of the show? Shimano's brand-new XTR Di2 groupset. Released in June (check out our fully geeked out deep dive on the new XTR Di2 here), this electronic drivetrain is so new that it hasn't yet landed on any stock builds we've received. Along with a handful of other upgrades and custom builds this summer, Joseph's Fourstroke is one of the first Di2 outfitted mountain bikes to roll through the shop, and it's as impressive as you would expect.

Ready to break it all down? Let's do it.

Drivetrain & Groupset: Wireless Precision, Wired to Win

As noted, the heart of this build and the star performer is Shimano's XTR Di2 electronic shifting, including shifters and rear derailleur. In our humble opinion, the precision and durability of this setup is unmatched: fast and whisper quiet, a familiar tactile feel (that XTR analog users know and love), and rock-solid when shifting under load. To pair with the XTR Di2, Joseph went a different route on the crankset, opting for SRAM X0 cranks, matched to an Alugear chainring. This blend gives him the stiffness and feel he prefers at the pedals, without sacrificing Shimano's flawless shifting out back. Towards the back, a Shimano XTR 10–51 cassette and XTR chain round out the drivetrain, while XTR brakes and 180mm rotors deliver consistent stopping power worthy of World Cup racing. Going a click deeper on the brakes, it's worth noting that Joseph is running 2-piston XC-oriented calipers with XTR enduro levers, which he believes will deliver the ultimate braking experience.

Suspension & Frame: Floats Like a Butterfly, Stings Like a Bee

Joseph started with the BMC Fourstroke 01 frameset, then swapped in the LT linkage to unlock 120mm of rear travel. Up front, he upgraded to a Fox Factory 34 Stepcast, netting out with 120mm of travel front and rear. These suspension choices bring Joseph's build on par with most of today's XC bikes, delivering enough cush to rip technical, chunky descents, while still maintaining the razor's edge precision and lightness the Fourstroke is known for. With pedals, bottle cages, and sealant, the build comes in at just under 25 pounds; fully raceable yet capable and confident on rowdier terrain.

Cockpit: Dialed and Decisive, Light and Fast

Split second decision making–shifting and braking, dropper post and lockout–is everything in XC racing and riding, and Joseph dialed in his setup with a BMC MFB 01 carbon handlebar, trimmed to 720mm for nimble steering, and a matching BMC stem. ESI Chunky grips help to minimize hand fatigue on technical trails and long haul rides, while Squidlock remote from Orbea integrates both suspension lockout and dropper control into a single ergonomic lever. The dropper is none other than BMC's Autodrop post, an 80mm travel marvel that lowers at the push of a button and returns lightning fast.

Wheels & Tires: With Ultimate 'Ground Control,' Houston, We Have No Problem

Light, stiff, and trusted by top riders worldwide, DT Swiss XRC 1501 carbon wheels with DT 240 hubs were Joseph's choice for ground control. Wrapped in Vittoria Mezcal 2.35 tires, the bike has a race-ready balance of rolling speed and grip, perfect for Utah's blend of hardpack, dust, and loose-over-hard conditions.

Finishing Touches: A Sharp Dressed Rig, Expertly Tailored

Rounding out the build is a Prologo Dimension NDR saddle, bottle cages, and clean internal routing that keeps the bike looking as sharp as it rides. Every piece is chosen for intent, and the result is a Fourstroke that represents not just the cutting edge of tech, but Joseph's years of experience helping riders chase their own dream builds.

Learn More

Thinking about your own custom build? Interested in building a bike from the ground up, or upgrading to Shimano's new XTR Di2?

Our team stands at the ready, and would love to help. Drop by the shop any time, send a message here, or give us a call at (801) 364-0344.

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