Engineered by Sirris. Tuned by Zero. The Sirris CMX F43 fork for the Zero XB combines a race-built F43 chassis with a symmetrical closed-cartridge damper system and two independent sealed dampers. With wide-range XB-specific tuning, adjustable compression and rebound, and direct-fit integration, it delivers sharp handling, confident control, and elevated front-end performance for real trail riding.

 

Sirris offers one weight range for the CMX F43 fork for Zero XB. (Listed weight range is rider weight without riding gear on. 15 pounds of riding gear is calculated into the weight ranges)

 

Architecture
Upside down fork

 

Travel
220 mm

 

Free length
775 mm

 

Fork Spacing
178 mm - allows for unlimited tire choice

 

Fork weight
4 kg per leg (driven by sturdy construction required for the forces and speeds encountered when pushing these bikes to their limits without compromising performance)

 

Stanchions
Ø43, high tensile steel with hard chrome

 

Outer tubes
Seamless 7050 aluminum, type 3 hard anodized coating

 

Drop outs
6061 aluminum, type 2 anodized coating
Replaceable caliper mount brackets allow for caliper and wheel upgrades

 

Brake mounting
• Sized for 220mm rotors, replaceable caliper mount brackets allow for caliper and wheel upgrades
• Zero XB 220mm rotor brake bracket is included

 

Axle
Ultra-high tensile hard chromed axle increases steering precision and confidence

 

Triple clamps
Billet 6061 aluminum, type 2 anodized coating, black

 

Steer tube 
Seamless 7050 aluminum, type 2 anodized coating

 

Stem mount
Designed for use with stock Zero Stem
(4-Bolt direct mount stem will not work with Zero dash mounts)

 

Top cap system
Motorcycle-style top cap allows for more consistent control over steering bearing tension 

 

Damping
• CMX tune (Compact Motocross Tune)
• Symmetrical and adjustable closed cartridge with spring backed modified IFP
• High-flow pistons + fully tunable compression and rebound valving
• Dual oil circuits for optimum performance. Separating lubrication and damping oils allows us to further optimize high and low speed damping performance.
• Balanced load, race-ready, high performance. No matter how hard you ride or how many laps you take, our closed cartridge forks will never fade and will always feel predictable.
• Hydraulic bump stop is a hydraulic bottom out control system that gives you soft landings and max stroke even on the most aggressive impacts.

 

Damper bodies
Seamless 7050 aluminum, type 3 hard anodized coating providing high durability and scratch resistance to keep your ride in top condition.

 

Rebound
Dual side high tensile steel spring, adjustable

 

Adjusters
External tool-free compression, rebound adjustment
(rebound adjusted using tool)

 

Seals
NOK MX seals 

 

Bushings
Daido MX bushings

 

Guards
High impact PP, 210-degree wraparound