Stumpjumper 15 Alloy Build from the Frame Up | 2025 Specialized

How to build a mountain bike from the frame up — in this video, I take a bare 2025 Specialized Stumpjumper 15 Alloy frameset and build it into a complete trail bike, start to finish. This build features Shimano's new wireless XT Di2 drivetrain, a 2026 FOX 36 Factory fork, and a Cascade Components 156mm mullet link paired with a FOX Float GENIE shock — the goal was a capable, reliable trail build without going completely overboard on cost. Whether you're building your first mountain bike or upgrading from a stock Stumpjumper 15, the process here applies to most modern trail frames — internal cable routing, wireless electronic shifting setup, brake bleeds, suspension install, and final tuning are all covered. Full parts list, build notes, and cost breakdown: https://mizubikes.com/posts/stumpjump... Timestamps: 0:00 What we're building 1:16 Full parts list & build goals 4:04 Build start & Cascade mullet link install 5:36 Rear brake hose routing & caliper install 6:44 Fox 36 steerer cut & fork install 8:05 Front brake lever & caliper install 8:50 Rear brake bleed 9:06 Crankset, bottom bracket & chain guide install 10:20 Rear wheel & brake adjustment 10:37 Wireless XT Di2 install & pairing 11:26 Rear derailleur adjustment 12:19 Front wheel & brake adjustment 12:35 Dropper post & saddle install 13:56 Final weight 14:09 Summary & closing thoughts Final Weight: 33 lb 12 oz (15.3 kg) Parts Used: Cascade Components 156mm Mullet Link — https://cascadecomponents.bike/produc... FOX Float Performance GENIE Shock FOX 36 Factory Fork Shimano XT Di2 Drivetrain — https://amzn.to/3R2klbC Shimano XT 12-Speed Chain — https://amzn.to/3QGyoDG BTLOS Carbon Wheels — https://btlos.com OneUp Chain Guide/Bash Guard — https://amzn.to/3R2k1JW OneUp Aluminum Pedals — https://amzn.to/4gotqpt OneUp V3 Dropper Post — https://amzn.to/3QWmG7X PRO Stealth Curved Saddle — https://amzn.to/4w4olr6 ODI Reflex Grips — https://amzn.to/4bdweSO What do you think about the mullet link setup on an alloy frame — worth it? Let me know in the comments. If you enjoyed the build, be sure to like and subscribe — ride review coming soon! #Stumpjumper15 #ShimanoXT #MTB #Specialized #MountainBike #BikeBuild #XTDi2 #FoxSuspension #CascadeComponents #TrailBike