CMX FOR ZERO XB
Ride It Once.
Regret Everything Else.
F43 CMX
The world’s best compact
e-moto fork. Period.
An oversized, race-built F43 chassis paired with our CMX-tuned closed cartridge damper — built for elite control, razor-sharp handling, and unreal front-end confidence. This is the strongest, most durable, highest performance fork available.
You need to ride it to believe it.
It’s that good.
F43 CMX Tune | Tool Free LSC | 220 mm Travel | Zero XB
Sirris offers two weight ranges when selecting your CMX Tune F43 fork for Zero XB. (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
Axle
Ultra-high tensile hard chromed axle increases steering precision and confidence
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
Damping
Symmetrical, adjustable closed cartridge with spring backed modified IFP
Damper bodies
Seamless 7050 aluminum, type 3 hard anodized coating
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
BUILT TO DOMINATE
ANY TERRAIN.
ANY TIME.
Full-size performance, compact-class versatility.
OVERSIZED TO OUTPERFORM
We took the race-proven F43 chassis — the gold standard in high-performance e-moto suspension — and resized and lightened it for compact e-moto. The result is a fork that rides like it belongs on a full-size race bike.
- Oversized 43mm stanchions, 7XXX-series hard-anodized uppers, and 775mm extended length deliver a longer, stiffer, more planted front end
- 220mm of terrain-devouring travel — 20mm more than stock
- Lightweight billet clamps (double bolt upper and lower) provide stiffness and resist twisting
- Wider 178mm fork spacing for unlimited tire choice
- Optional drop crown enables a 21” front wheel or a taller front end (extended to 800mm)
- Direct mount stem compatibility
- Replaceable brake caliper adapters and swappable wheel spacers for cross-compatibility with future bikes
- Custom ultra-stiff, race-grade chromoly axle maximizes control, steering precision, and predictability
- Motorcycle-style top cap allows for more consistent control over steering bearing tension
- 43mm hard chrome stanchions resist flex, dents, and nicks
- 7XXX-series hard-anodized uppers for maximum strength and durability
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.
Consistent. Predictable. Endlessly tunable.
CMX is the difference you feel from the first twist of the throttle.
CMX TUNE
DOMINATE THE TRACK
The Compact Motocross Tune F43 is an unapologetic race fork, built for elite-level racers chasing podiums—but it's just as powerful in the hands of everyday rippers looking to level up. Razor-sharp when you push it, forgiving when you need it. This is the ultimate performance upgrade.
FULL SPEED. FULL CONTROL. NO COMPROMISE.
The CMX Tune is purpose-built for the high-speed demands of the lightweight e-moto class—engineered to dominate any terrain, any time, anywhere. Whatever you throw at it, it’s ready.
CMX TUNE
DOMINATE THE TRACK
The Compact Motocross Tune F43 is an unapologetic race fork, built for elite-level racers chasing podiums—but it's just as powerful in the hands of everyday rippers looking to level up. Razor-sharp when you push it, forgiving when you need it. This is the ultimate performance upgrade.
FULL SPEED. FULL CONTROL. NO COMPROMISE.
The CMX Tune is purpose-built for the high-speed demands of the lightweight e-moto class—engineered to dominate any terrain, any time, anywhere. Whatever you throw at it, it’s ready.
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.
CMX Tune Starting point notes:
- Assuming neutral riding position, and 15 lbs gear
- Weights of upgrades (battery, controller, etc) to be added to rider weight
- Riders close to a weight cut off need to adjust preload to compensate
- Very aggressive/pro riders to consider +1 weight class and drop preload to get sag. Especially if in the upper range.
- Rider preference and riding conditions may require a different setup
Example:
- 160 lb rider without riding gear, 20 additional lbs with upgraded controller/battery
- Weight calculation 160+20=180
- Aggressive rider = Heavy tune with low preload
- Relaxed rider = Medium tune with high preload
OWNER'S GUIDE
F43 CMX fork for compact size E-motos: E-Ride Pro SR and 3.0, Surron LBX, Talaria MX5, Ventus One+, and more.
