2025 Specialized Stumpjumper 15 Alloy frame in raw aluminum finish, ready for component swap in workshop setting

2025 Specialized Stumpjumper 15 Alloy frame in raw aluminum finish, ready for component swap in workshop setting

Wondering how to plan a mountain bike frame swap without replacing all your components? I’m preparing to swap my Specialized Stumpjumper EVO Alloy over to the 2025 Stumpjumper 15 Alloy—and I’m sharing exactly what will carry over, what needs replacing, and what to look out for, especially if you’re running a mullet setup.

If you’re considering a similar upgrade, this post will help you avoid surprises and plan the smoothest bike frame swap possible.

Why I’m Doing a Frame Swap

My EVO build has been dialed for trail riding, but the Stumpjumper 15 Alloy offers a lighter frame, more efficient suspension, and modern geometry. Instead of starting from scratch, I’m swapping the frame and keeping most of my current setup—making this a budget-friendly upgrade path for anyone with solid components already in place.

Specialized Stumpjumper EVO Alloy mullet setup with RideFast 29' front wheel and BTLOS 27.5' rear wheel in a home workshop setup

Specialized Stumpjumper EVO Alloy mullet setup with RideFast 29’ front wheel and BTLOS 27.5’ rear wheel in a home workshop setup

My Current Stumpjumper EVO Alloy Build

  • Drivetrain: Shimano XT crankset, XT cassette, XT chain
  • Rear Derailleur: Shimano SLX 12-speed
  • Brakes: Shimano Saint 4-piston
  • Fork: RockShox Lyrik Ultimate 160mm
  • Shock: RockShox Super Deluxe (210x55mm, standard eyelet)
  • Wheels:
    • Front: RideFast 29" carbon
    • Rear: BTLOS 27.5" carbon with DT Swiss hub (mullet setup)
  • Cockpit: OneUp carbon bars, Deity stem, ODI Elite grips
  • Dropper Post: OneUp 30.9mm dropper with 34.9mm shim
  • Pedals: OneUp alloy

What Will Transfer to the New Frame

ComponentCarries Over?NotesDrivetrainYesXT crankset fits the BSA 73mm threaded bottom bracketBrakesWith modsSaint brakes work, but the rear hose may need to be replacedCockpitYesBars, stem, and grips transfer directlyDropper PostYes (with shim)30.9mm post works with a 34.9mm shim; a native 34.9mm post would be cleanerForkYesStumpjumper 15 supports both 150mm and 160mm forks—my Lyrik is 160mmFront WheelYes29" RideFast carbon wheel fits perfectly in the new fork/frame

What Won’t Transfer (Yet)

  • Rear Wheel (27.5") – My BTLOS mullet rear wheel won’t fit the Stumpjumper 15 until I install the mullet link, which is currently out of stock.
    Temporary plan: I’ll run a full 29” setup using a matching rear wheel until I can convert back to mullet.
  • Rear Shock: The Stumpjumper 15 comes with a GENIE 210x55mm shock, so I’ll be using that instead of transferring the Super Deluxe.
  • Cables & Housing: Internal routing differs; I’ll replace shift housing, dropper cable, and rear brake hose.
  • Chainguide/Bashguard: I’ll check ISCG mount compatibility and hardware.

What I’ll Need to Buy

Tips on How to Plan a Mountain Bike Frame Swap

  • Use the swap to refresh parts: Unless your cables and housing were just replaced, this is a great time to start fresh.

  • Rear brake hose usually needs replacing: The front hose often works fine. The rear hose likely won’t unless you have enough extra length to re-trim the barb and olive.

  • Always plan for a brake bleed.

  • Fork steerer tube check: Compare head tube lengths between the old and new frame. Measure how much steerer tube you have above the headset with your stem installed to ensure it’s long enough for the Stumpjumper 15.

  • The Stumpjumper 15 Alloy is compatible with both 150mm and 160mm forks, so keeping my 160mm Lyrik is an easy choice.

  • Organize everything: Label bolts and small parts or bag them by section during disassembly.

  • Clean and inspect components while everything is apart—especially bottom bracket threads, headset bearings, and crank interfaces.

  • See our full guide on beginner bike repair tools

Final Thoughts

Now you know how to plan a mountain bike frame swap from start to finish. With a little prep, most components from my EVO build will transfer to the Stumpjumper 15 Alloy. I’ll start with a full 29” setup and switch back to mullet as soon as the link is back in stock.

Stay tuned for the full build reveal and ride impressions coming soon to mizubikes.com.