Gasbox Full Frames & Lowbrow Customs Hardtails

Harley Hardtail Frames for Sportster & Big Twin

A motorcycle hardtail frame does one thing: it removes the rear suspension for that classic rigid chopper stance. This collection covers two different paths to get there, weld-on and bolt-on hardtail conversions for an existing frame, and complete Gasbox rigid frames built from scratch.

Hardtail Conversions vs. Complete Frames

Weld-on and bolt-on hardtail rear sections attach to an existing frame, a lower-cost route for riders keeping their current front end and neck. Bolt-on sections, like the KR-style and straight-leg options for Ironhead Sportsters, skip welding entirely. Weld-on sections cover a wider range of models, including Panhead and Shovelhead Big Twins, but require a welder to install, along with new frame hardware. Complete Gasbox rigid frames replace the whole frame, which is the better route for a from-scratch build or when frame geometry needs to change along with the conversion.

Fitment by Model

This collection covers Harley-Davidson Sportster frames across multiple year ranges, Ironhead Sportsters, Big Twin frames in both 4-speed and 5-speed configurations, Panhead and Shovelhead models, and Triumph Unit 500cc and 650cc frames. Full Gasbox frames also come in Frisco or Sporty tank mount configurations, with or without a horseshoe oil tank, and with a disc brake rear option on Ironhead builds.

Frame Geometry and Alignment

Gasbox full frames are offered in "3 Up" chopper geometry alongside standard rigid options, changing the stretch and stance of the finished bike. Once the frame is set, most builders move on to mounting a rear fender, sissy bar, and kickstand to the new rear section. Frame geometry, tank mount style, and oil tank compatibility all need to match the rest of the build before ordering, so check the product listing closely for the exact model, year, and configuration needed.