Diaz Suspension Design

Runt Cartridge Fox 36/Marz Z1, 150 (-'25)/140("26+)

The Diaz Suspension Design Runt Cartridge is a dual-chamber air spring cartridge upgrade built to give a more linear, coil-like compression feel in a Fox 36 or Marzocchi Z1 Bomber Air—without giving up the pressure-based adjustability riders rely on for changing terrain, rider weight, and riding style.

Designed as a drop-in air spring replacement, the Runt adds a secondary air chamber with its own valve so progression can be tuned directly—helping riders balance small-bump sensitivity, mid-stroke support, and bottom-out resistance more precisely than standard volume spacers alone.

Why riders choose a dual-chamber air spring

1. Near-linear spring curve - Targets a more consistent, “coil-like” feel through the stroke for improved traction and comfort
2. Secondary air chamber + valve - Adds built-in tunable progression to dial bottom-out resistance without relying solely on tokens/spacers
3. Mid-stroke support focus - Helps the fork ride higher when pushing hard while preserving compliance on chatter
4. Drop-in cartridge format - Streamlines installation compared to piecing together multi-part air spring changes
5. Weight-conscious alternative - Designed to be about 1/2 lb lighter than typical coil conversions, while staying close to token/spacer-based setups (about +20 g)

This 36mm version fits 2018+ Fox 36 forks with the NA2 air spring and Marzocchi Z1 Bomber Air forks. Not compatible with NA1 air springs, Z1 Coil forks, or Fox 36 E-Bike forks. Travel fitment: 150mm (through ’25) / 140mm (’26+).