Sirris F43 CMX Tune Front Fork | Surron Light Bee X
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Sirris F43 CMX Tune Front Fork | Surron Light Bee X
Description
Meet the Sirris F43 CMX Fork — the world’s best compact e-moto fork, period. Built on the oversized, race-proven F43 chassis and tuned with the CMX closed-cartridge damper, this fork delivers unreal control, razor-sharp handling, and front-end confidence that no stock fork can match. Strong, durable, and endlessly tunable — this is the fork elite racers and everyday rippers have been waiting for.
It’s not just stiffer — it delivers strength without compromise.
Everything is designed to improve balance, eliminate flex, soak up punishment, and offer long-haul durability with adjustability for riders who push harder
Why You’ll Want It
⚡ Full-Size Performance in Compact Form – The legendary F43 chassis re-engineered for today’s most popular light e-motos.
⚡ 220mm of Travel – More stroke, more control, more fun.
⚡ Oversized 43mm Stanchions – Stiffer, stronger, and built to take a beating.
⚡ CMX Closed Cartridge – Pro-level damping with independent compression & rebound control.
⚡ Tool-Free Compression Adjusters – Nearly 30 clicks of quick tuning, no tools required.
⚡ Wider 178mm Fork Spacing – Run dirt or street tires without limits.
⚡ Direct-Mount Stem Ready – Maximum stiffness and steering precision.
⚡ Optional Drop Clamp – Run a 21” front wheel and raise the front end 25mm.
Sirris offers two weight ranges when selecting your CMX Tune F43 fork for Surron Light Bee X (LBX). (Listed weight ranges are rider weight without riding gear on. 15 pounds of riding gear is calculated into the weight ranges)
140 lbs - 180 lbs (Medium = 3.6/3.2 springs)
180 lbs - 220 lbs (Heavy = 3.6/3.6 springs)
Fork spring rates listed above are left side/right side.
FORK SPECS:
Architecture
Upside down fork
Travel
220 mm
Free length
775 mm
(drop clamp option adds another 25mm of extended length)
Fork Spacing
178 mm - allows for unlimited tire choice (dirt or street)
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
Rotor fitment: LBX comes stock with a 200mm rotor which will need to be upgraded to 220mm
• Sized for 220mm rotors, replaceable caliper mount brackets allow for caliper and wheel upgrades
• 220mm rotor brake bracket is included
Axle
• Custom ultra stiff, race-grade ultra-high tensile hard chromed axle increases steering precision and confidence
• Surron LBX wheel spacers included
Triple clamps
Billet 6061 aluminum, type 2 anodized coating, 2 color options (blue, black)
Optional drop clamp allows for 21” front wheel conversion (black only)
Steer tube
Seamless 7050 aluminum, type 2 anodized coating
Stem mount
4-bolt direct mount stem only
Stem fitment: The stock LBX stem is not compatible because the Sirris steerer tube cannot be clamped. We recommend Warp9 or the “Heavy Hitter Adjustable Billet Display Mount” from Gritshift.
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
If you have any questions, you are always welcome to contact us. We'll get back to you as soon as possible, within 24 hours on weekdays.
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