BC40 SRAM XX SL Eagle Transmission Bike

The Allied BC40 marks the Arkansas-based brand's entry into mountain biking, arriving as a premium, US-made cross-country and marathon platform. Designed around 120mm of front and rear travel, the carbon frame utilizes a linkage-driven single-pivot suspension layout with flex stays to keep weight low and mechanical complexity to a minimum. While it can be configured with shorter-travel components for pure cross-country racing, its stock form leans heavily into modern endurance riding. The BC40 is built for riders who prioritize pedaling efficiency and long-distance speed but want enough suspension capability to handle technical descents without feeling overwhelmed. It stands out in a crowded market not just for its domestic manufacturing and custom paint options, but for its distinct blend of hardtail-like acceleration and composed trail manners.

$12,900

Allied BC40 SRAM XX SL Eagle Transmission Bike

Build

Size

Inventory

Allied

Size M

$12,930

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Stack	609mm
Reach	445mm
Top tube	596mm
Headtube length	105mm
Seat tube length	420mm

Fit and geometry

The BC40 utilizes progressive geometry that bridges the gap between traditional cross-country twitchiness and trail bike stability. A 66.5-degree head tube angle pushes the front wheel out just enough to calm the steering on steep descents, while a 76-degree seat tube angle keeps the rider centered and upright over the bottom bracket for efficient climbing. This combination creates a comfortable, forward-leaning posture that reduces lower back fatigue during marathon events.

Reach measurements are modern but moderate, sitting at 445mm for a size medium, which pairs well with the stock 50mm stems to keep the steering direct. The 435mm chainstays are consistent across all four frame sizes, balancing rear-wheel traction on climbs with maneuverability in corners. Allied opted for a low bottom bracket to enhance cornering grip, though this requires some pedal awareness in rocky terrain. The frame also features a notably stout construction, providing excellent lateral stiffness that prevents the chassis from flexing unpredictably when pushed hard into berms or through technical compressions.

Full specs

Frameset

Fork

RockShox SID Ultimate Flight Attendant 120

Groupset

Shift levers

SRAM AXS Pod Ultimate

Rear derailleur

SRAM XX SL Eagle Transmission

Cassette

SRAM 1299 XX SL Eagle 10-52

Chain

SRAM XX T-TYPE Flat Top

Crankset

SRAM XX SL Eagle Transmission Power Meter

Bottom bracket

SRAM Dub 73 BSA

Front brake

SRAM Motive Ultimate Stealth 4 Piston

Rear brake

SRAM Motive Ultimate Stealth 4 Piston

Front rotor

180mm

Rear rotor

160mm

Wheelset

Front wheel

Zipp 1Zero HiTop SW Carbon

Rear wheel

Zipp 1Zero HiTop SW Carbon

Front tire

Vittoria Mezcal XC Race 29x2.4 Tires

Rear tire

Vittoria Mezcal XC Race 29x2.4 Tires

Cockpit

Stem

ALLIED Duet

Handlebars

ALLIED Duet HB08 Carbon Flat Bar

Saddle

Selle Italia Novus Boost Superflow

Seatpost

Rock Shox Reverb AXS

Grips

ESI Chunky

Builds

The BC40 lineup is positioned firmly in the premium tier, with no true budget options available. The range starts with a highly capable Shimano XT mechanical build featuring Industry Nine 1/1 Trail S wheels and Fox Performance suspension. Moving up the ladder introduces wireless shifting, starting with SRAM GX Eagle Transmission and progressing through X0 Eagle Transmission and Shimano XTR Di2. These mid-tier builds upgrade to lighter Industry Nine carbon wheelsets and top-tier Fox Factory or RockShox Ultimate suspension components.

At the pinnacle of the range, the SRAM XX SL Eagle Transmission build spares no expense, outfitting the bike with RockShox Flight Attendant automated suspension, Zipp 1Zero HiTop SW carbon wheels, and an integrated power meter. Across all builds, Allied prioritizes durability and ease of maintenance, utilizing a standard 73mm threaded bottom bracket, a SRAM Universal Derailleur Hanger, and external cable routing ports on the head tube rather than routing lines through the headset. While the absolute cost is high, the value lies in the domestic manufacturing, the inclusion of high-strength Innegra fibers in the carbon layup, and the premium component specification at every tier.

Shimano XT M8100 Bike

$6,730

SRAM GX Eagle Transmission Bike

$6,885

SRAM X0 Eagle Transmission Bike

$8,730

Shimano XTR M9200 Di2 Bike

$11,050

SRAM XX SL Eagle Transmission Bike

$12,900

Selected

Reviews

Reviewers consistently praise the Allied BC40 for its urgent acceleration and remarkable pedaling platform. Testers found the bike highly resistant to pedal bob, translating power so effectively that many questioned the need for a remote lockout. This efficiency creates a "lively, snappy ride that’s nothing short of addicting" (Gearpatrol) on rolling terrain and steep climbs. Rather than relying on heavy compression damping, the suspension kinematics provide a firm, supportive feel that rewards aggressive pedaling.

When pointed downhill, the bike surprises riders with its stability. The suspension manages to feel "composed and stuck to the ground" (PinkBike) through rough sections, allowing pilots to relax and look further down the trail. Some testers noted the ride quality tends to "skip over the top of bumps" (Bicycling) rather than plowing through them, favoring an active riding style.

The primary tradeoff for this high-speed stability is a slight reduction in low-speed agility. In extremely tight, uphill switchbacks, the slack front end "requires more steering input and brain output" (PinkBike) compared to steeper, traditional race bikes. Additionally, a few reviewers reported that the wide seatstays occasionally rubbed against their knees or calves during out-of-the-saddle efforts. Despite these minor quirks, the consensus points to a highly capable marathon machine that excels at covering varied terrain quickly.