SIRRIS F43 SX TUNE FORK FOR SURRON ULTRA BEE
Proven at the highest level. Built from real-world feedback.
F43 SX Tune | Tool Free LSC | 260 mm Travel | Surron Ultra Bee 1.2
PRO RIDERS ONLY
Now featuring tool-free LSC adjustment, Torx fasteners, and updated graphics.
SX Tune is built for the biggest hits, hardest landings, and highest speeds. SX Tune is our stiffest, most aggressive suspension setup, engineered for pro-level riders who demand maximum support when pushing the limits. PRO-LEVEL RIDERS ONLY.
RIDER WEIGHT SPECS:
Sirris offers two weight ranges to choose from when selecting your SX Tune F43 fork. (Listed weight ranges are rider weight without riding gear on. 15 pounds of riding gear is calculated into the weight ranges)
< 160 lbs (Light = 5.4/5.0 springs)
> 160 lbs (Medium = 5.8/5.0 springs)
Fork spring rates listed above are left side/right side.
FORK SPECS:
Architecture
Upside down fork with symmetrical and adjustable pressurized closed cartridge dampers
Travel
260 mm
Free length
856 mm
Fork weight, includes clamps and steerer
22 lbs / 10kg
Stanchions
Ø43, high tensile steel with hard chrome
Outer tubes
Seamless 7050 aluminum, type 3 hard anodized coating
Drop outs
Forged 6061 aluminum, type 3 hard anodized coating
Brake mounting
Sized for stock Ultra Bee calipers and 240mm rotors
Triple clamps
Billet 6061 aluminum, type 2 anodized coating, 2 color options (blue, black)
Steer tube
Seamless 7050 aluminum, type 2 anodized coating
Damping
• SX tune
• Symmetrical and adjustable closed cartridge with spring backed IFP
• High-flow pistons and fully tunable compression and rebound valving
• Dual oil circuits for optimum performance. Separate oil circuits deliver optimized damping and lubrication performance.
• Balanced, race-ready, high performance. No matter how hard you ride or how many laps you put in, Sirris closed-cartridge forks deliver consistent, fade-resistant performance and predictable handling lap after lap.
• The hydraulic bump stop system provides progressive bottom-out control, delivering softer landings and maximum usable travel, even under 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.
Spring
Dual side high tensile steel spring, adjustable preload
Adjusters
External tool-free compression, rebound adjustment
(rebound adjusted tooled to ensure durability in the harshest environments)
Seals
NOK Heavy Duty seals
Bushings
Premium Daido bushings (Custom Sirris proprietary design)
Guards
High impact PP, 210-degree wraparound
Across all three tunes—Trail, MX, and SX—the F43 also receives a new tool-free top-cap adjustment system with the signature Sirris blue adjuster, bringing quick, tool-free adjustability directly to the rider. Whether making changes at the track, on the trail, or between sections, suspension adjustments are now faster and easier to access.
Durability and serviceability also get an upgrade with the introduction of Torx fasteners across the F43 platform. The new fasteners provide greater resistance to rounding compared with traditional tool interfaces, delivering a more robust solution for riders, technicians, and professional-level service environments.
Completing the update is an all-new fork guard decal package across Trail, MX, and SX models, giving the F43 a fresh, unmistakably Sirris appearance to match the performance underneath.
TUNING DETAILS & RIDER WEIGHT RANGE
Listed weight ranges are body weight without riding gear (15 pounds of riding gear is calculated into the weight ranges).
Weights of upgrades (battery, controller, etc) need to be added to rider weight.
SX TUNE Starting point notes:
This is the starting point based on feedback from test riders and calculations. Assuming neutral riding position, and 15lbs gear
- We recommend SX tune for pro-level riders only
- Assuming aggressive riding position, and 15lbs gear
- Stock bike with 18/21
- Weights of upgrades (battery, controller etc) to be added to rider weight
- Rider preference and riding conditions may require a different setup
Example:
- 150 lb rider without riding gear, 15lbs gear, 10lbs upgrades
- Weight calculation 150+2x10=170lbs.
- Medium Tune recommended
SETTINGS NOTE: Settings are number of clicks from the closed position (full clockwise). Once they are in the closed position, back them out (counter-clockwise) according to the number of clicks indicated in the chart above to get you to factory settings.
*OIL NOTE: Sirris uses Shell Tellus S2 VX15 (5wt) in the fork cartridge and Shell Tellus S2 VX68 (20wt) as the bath oil. These are cross compatible with other high quality 5wt and 20wt suspension fluids. Sirris uses a semi-synthetic 2.5wt oil in the shock that is also compatible with other high quality 2.5wt aftermarket suspension fluids. You can use 5wt/20wt oils of your preference, Lubefinder.com can be used to source the fork oils. KYB K2C can be used in the shock and has wide availability.
TECH HELP
Suspension setup, owner's guide, tech help, warranty and more. Learn how to properly set up, use, and maintain your new Sirris suspension products.
