Brother Cycles Big Bro Adventure Frameset
Brother Cycles Big Bro Adventure Frameset
- 4.9 from 782 Google reviews
- Independent Bike Dealer of the Year 2025, BikeBiz Awards
- UK delivery from £4.99, or free collection from our Bow shop at E3 3XS.
- Checked by our team before it leaves us
Collecting instead? Email us or message us on WhatsApp before you visit, so we can have it ready for you.
A tough-as-nails 29er and 27.5+ steel adventure frame, from bikepacking races to round-the-world touring.
The Big Bro is built for going a long way off the beaten track. Run it light for a bikepacking race, load it with front and rear panniers for a big tour, or strip it back for the trails. It has finished the Tour Divide and the Silk Road Mountain Race, and it will handle the North Downs Way without noticing.
The latest version uses heat treated 4130 chromoly, new rail-style sliding dropouts for a stronger rear end, a SRAM UDH hanger that takes Full Mount derailleurs, top tube bag mounts and extra rack mounts on the fork. Boost spacing clears 29 x 2.6 inch or 27.5 x 3 inch tyres. Brother's next batch of Big Bros is due in November 2026.
Why we chose this for our customers:
- Go anywhere: 29 x 2.6 inch or 27.5 x 3 inch tyres on Boost spacing
- Geared, single speed or Rohloff: sliding dropouts, with a Rohloff dropout kit available
- Mounts everywhere: triple mounts on and under the down tube, on the fork legs, top tube bag mounts and rack mounts
- Modern standards: UDH hanger, stealth dropper routing, 44mm head tube
- Proven: tested on the South Downs, Snowdonia and the Highlands, then raced across continents
Specification
- Frame: heat treated 4130 chromoly, double butted main triangle, ED coated
- Fork: 4130 chromoly tapered unicrown, 100mm suspension corrected, 15x110mm Boost thru axle included
- Rear: Boost 12x148mm thru axle included, sliding rail dropouts, SRAM UDH hanger
- Brakes: 51mm IS disc mount, 180mm max rotor
- Tyre clearance: 29 x 2.6 inch or 27.5 x 3.0 inch
- Seatpost: 30.9mm, stealth dropper routing, 33.1mm seat clamp included
- Headset: ZS44/28.6 upper, EC44/40 lower (not included)
- Bottom bracket: 73mm ISO threaded
- Chainrings: 48-36-26t triple, 44-30t double, 38t single
- Weight: 2.60kg frame (medium), 1.37kg fork
- Tested to ISO 4210 MTB standard, three year frame guarantee from Brother Cycles
Geometry
| Size | S (16) | M (18) | L (20) | XL (22) |
|---|---|---|---|---|
| Seat tube (C-T) | 406 | 457 | 508 | 559 |
| Effective top tube | 575 | 595 | 620 | 645 |
| Head tube | 95 | 100 | 110 | 125 |
| Head angle | 69.5 | 70 | 70.5 | 70.5 |
| Seat angle | 73 | 73 | 73 | 73 |
| Chainstay (min) | 445 | 445 | 445 | 445 |
| Stack | 598 | 605 | 616 | 630 |
| Reach | 392 | 410 | 432 | 452 |
| Wheelbase | 1083 | 1098 | 1118 | 1144 |
All measurements in mm and degrees.
Ideal for: bikepackers, expedition tourers and riders who want one tough steel mountain bike that can carry everything.
Brother design their frames in London and we build them up on the bench in Bow, a few miles across East London. Bring us a parts list, a pile of components you already own, or just an idea, and we will spec, build and fit it for you. See the full Brother Cycles range, our other framesets, or book a build through our workshop.