Sirris CMX Tune F43 Fork | Arctic Leopard XE Pro R

The Sirris CMX Tune F43 Fork is a serious suspension upgrade built for riders pushing the Arctic Leopard XE Pro R harder than a standard fork was designed to handle. With 220mm of travel, 43mm high-tensile steel stanchions, a symmetrical closed-cartridge damping system, hydraulic bottom-out control, and billet aluminum triple clamps, the F43 is designed around control, consistency, and durability at higher speeds and under heavier impacts.

The CMX, or Compact Motocross Tune, gives the F43 a performance-focused setup for aggressive trail riding, jumps, hard braking, rough terrain, and repeated high-speed hits. Sirris uses separate lubrication and damping oil circuits, high-flow pistons, tunable compression and rebound valving, and a spring-backed modified IFP to keep the fork predictable as riding intensity increases.

For the Arctic Leopard XE Pro R, Sirris includes the required wheel spacers and a 240mm rotor brake bracket. Replaceable caliper mounting brackets also give riders more flexibility for future brake, caliper, rotor, and wheel upgrades.

Rider Weight & Spring Options

Sirris offers two rider weight ranges when selecting the CMX Tune F43. Listed weights are the rider's weight without riding gear. Sirris calculates approximately 15 pounds of riding gear into these ranges.

• 140 lbs to 180 lbs: Medium, 4.0 / 3.6 springs
• 180 lbs to 220 lbs: Heavy, 4.0 / 4.0 springs

Fork spring rates are listed as left side / right side.

Fork Specifications

• Architecture: Upside-down fork
• Travel: 220mm
• Free Length: 775mm, 800mm total length with drop clamp
• Fork Spacing: 178mm, allowing extensive dirt or street tire options
• Fork Weight: 4 kg per leg
• Stanchions: 43mm high-tensile steel with hard chrome
• Outer Tubes: Seamless 7050 aluminum with Type 3 hard-anodized coating
• Dropouts: 6061 aluminum with Type 2 anodized coating
• Brake Mounting: Sized for 240mm rotors
• Brake Bracket: 240mm rotor brake bracket included
• Axle: Custom ultra-stiff, race-grade, ultra-high-tensile hard-chromed axle
• Triple Clamps: Drop clamp, billet 6061 aluminum, Type 2 anodized coating, black
• Steer Tube: Seamless 7050 aluminum with Type 2 anodized coating
• Stem Mount: 4-bolt direct-mount stem only
• Seals: NOK MX seals
• Bushings: Daido MX bushings
• Guards: High-impact PP with 210-degree wraparound coverage

CMX Closed-Cartridge Damping

The F43 uses Sirris' CMX Tune symmetrical closed-cartridge system with a spring-backed modified IFP. High-flow pistons and fully tunable compression and rebound valving give riders more control over how the fork reacts to braking, repeated impacts, jumps, and changing terrain.

• Dual Oil Circuits: Separate lubrication and damping oils help optimize both high-speed and low-speed damping performance.
• Hydraulic Bump Stop: Hydraulic bottom-out control helps soften hard landings while allowing riders to use the available fork stroke.
• Damper Bodies: Seamless 7050 aluminum with Type 3 hard-anodized coating for durability and scratch resistance.
• Rebound: Dual-side high-tensile steel spring, adjustable.
• Adjustments: External compression and rebound adjustment. Compression is tool-free, while rebound adjustment requires a tool.
• Top Cap System: Motorcycle-style top cap provides more consistent control over steering bearing tension.

Built for Hard Riding

At 4 kg per fork leg, the F43 is not designed around being the lightest fork possible. Its sturdy construction is intentional, giving the front end the strength and rigidity needed to deal with the forces, speeds, braking loads, and impacts generated by the high-performance Arctic Leopard XE Pro R. The custom race-grade axle further increases front-end stiffness to improve steering precision and rider confidence.

The 178mm fork spacing also leaves plenty of room for tire selection, whether the XE Pro R is being built around an aggressive dirt setup or a street-oriented wheel and tire combination. Replaceable caliper mount brackets add another level of flexibility for riders planning future brake or wheel upgrades.

Fitment

• Arctic Leopard XE Pro R

Fitment Note: Arctic Leopard XE Pro R wheel spacers and a 240mm rotor brake bracket are included.

Who Is the F43 For?

The Sirris F43 makes the most sense for Arctic Leopard XE Pro R riders who are starting to find the limits of the stock front suspension. Its combination of 220mm travel, closed-cartridge damping, hydraulic bottom-out control, 43mm stanchions, NOK MX seals, and Daido MX bushings is particularly useful when consistent damping and front-end control matter more than simply reducing weight.

• Aggressive trail and enduro riders dealing with rocks, roots, braking bumps, drops, and technical terrain.
• Jump and track riders who need better bottom-out control and consistent damping through repeated hard impacts.
• High-performance Arctic Leopard XE Pro R builds where increased speed, braking force, larger tires, or upgraded brakes demand a stronger and more tunable front suspension setup.