Surly

Lowside Frameset - Blue Monday

Surly Lowside Frameset - Blue Monday is a steel mountain bike frameset built for riders who want a simple, durable platform that’s equally comfortable ripping local singletrack or rolling across town. With plus-tire clearance, modern axle standards, and singlespeed-first details, the Lowside keeps the build straightforward while leaving room to tune traction, comfort, and control with tire choice and cockpit setup.

Key advantages for a clean, fun trail build

1. 4130 Chromoly steel chassis - Uses a 100% Surly 4130 Chromoly frame with a double-butted main triangle for a strong, serviceable foundation with classic steel ride feel
2. Plus-tire clearance - Designed around 26” x 3.0” or 27.5” x 2.8” tires to deliver high-grip traction and added comfort on rough trails without overcomplicating the bike
3. Thru-axle compatibility (axles included) - Front and rear Surly thru-axles are included for precise wheel alignment and confident handling under load
4. Gnot-Boost rear spacing - Provides flexible hub spacing options to simplify wheel sourcing and support a wide range of modern mountain wheel builds
5. Dropper-ready routing - Internal routing supports a cleaner dropper post setup, and the 30.9mm seat tube ID opens up broad dropper compatibility
6. Singlespeed-specific design - Built around the simplicity of singlespeed trail riding, with a derailleur hanger present but no Trip Guides for a cleaner, SS-focused frame