Our all purpose, tough as nails 29er/27.5+ adventure frame; designed to take you well off the beaten track and beyond. Whether you’re running a lightweight bikepacking setup, front and rear panniers for a fully loaded ’round-the-world’ tour or just stripped back to thrash some forest trails the Big Bro can handle it.
New for 2025 // with the following updates the Big Bro is now an even more capable adventure frame – heat treated 4130 chromoly main triangle, new configuration sliding dropouts for a stronger and more reliable rear end, UDH full mount compatible rear mech hanger, top tube bag mounts and additional front rack mounts.
The frame is now constructed out of extra tough ‘heat treated’ 4130 double butted cro-mo tubing and comes with a 100mm suspension corrected fork, both with corrosion resistant ED coating applied. The Big Bro features Boost spacing which means there’s clearance for big 27.5 x 3″ tyres or 29 x 2.6″ tyres if you’d prefer to go with a 29er setup. It features stealth dropper routing, multiple rack and bag mounts, a bottle mount on the seat tube and triple mounts on and under the down tube for extra bottles and storage. The Big Bro fork also features triple mounts to fit further bottle cages or Anything Cages.
The rear triangle features S-bend chainstays with replaceable alloy thru axle sliding dropouts for geared or singlespeed setups. These have been re-designed for 2025 to now feature a rail system for extra strength and reliability.
Brother Cycles - Big Bro - 2025 - Frameset
FEATURES
Tubing: - 4130 Heat Treated Chromoly steel - double-butted main triangle, ED coated
Brake compatibility; 51mm IS disc brake mount, 180mm max rotor size
Dropouts: Boost 12x148mm thru axle (included)
Gear Hanger: SRAM UDH type, full mount compatible
Seat post diameter: 30.9mm
Seat clamp diameter: 33.1mm (included)
Headset: 44mm, SHIS ZS44/28.6 upper, EC44/40 lower (not included)
Front derailleur clamp diameter: 34.9 mm top pull or high direct-mount (adapter available separately)
Bottom bracket shell: 73mm bottom bracket, ISO threaded
Maximum tyre clearance: 29" x 2.6", 27.5" x 3.0" (note: not all drivetrains allow for these maximum tyre clearances)
Fork : 4130 Chromoly tapered unicrown fork, ED coated. 15x110mm Boost thru axle (included)
Full-length cable housing guides for derailleurs and brakes
3 sets bottle cage mounts on all sizes
Chainring clearance: 48-36-26t triple, 44-30t double, 38t single
Weight: medium (18") frame 2.60kg, fork (300mm steerer) 1.37kg
Tested to ISO 4210 MTB standard
