Surron Ultra Bee

F43 MX Tune Fork | LSC | 246mm Travel

The Sirris F43 Fork with MX Tune is built for one thing—motocross domination. If your Ultra Bee spends more time in the air than on the ground, this is your setup. With firm suspension dialed for balance, control, and serious bottoming resistance, it’s the go-to fork for riders hitting big jumps, blasting whoops, and railing corners at top speed.

Trade a bit of trail plushness for pure motocross performance—and gain the confidence to send it harder, faster, and higher.

Want the complete set up - pair with the R46 MX Shock!

Why Riders Choose MX Tune 🏁

• Motocross-Specific Valving – Firm and supportive for aggressive riding

• Bottoming Resistance – Built to handle huge jumps and gnarly landings

• Race-Ready Control – Stable through whoops and fast cornering

• Proven E-Moto Performance – Designed for the Surron Ultra Bee

Rider Weight Options ⚡️

Choose the right spring rates (weights listed without gear—add 15 lbs for riding gear):

• 120–160 lbs → Light (4.4/4.4 springs)

• 160–200 lbs → Medium (5.0/4.8 springs)

• 200–240 lbs → Heavy (5.4/5.0 springs)

• 240–280 lbs → X Heavy (5.4/5.4 springs)

• 280–320 lbs → XX Heavy (5.4/5.4 springs)

TUNING DETAILS & RIDER WEIGHT RANGE

MX Tune Starting point notes:

• Assuming neutral riding position, and 15 lbs gear
• Weights of upgrades (battery, controller, etc) to be added to rider weight
• Stock bike with 18/21 wheels
• 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
• XX Hvy same spring rates as X Hvy due to maxed out rear spring rate

Example:

• 180 lb rider without riding gear, 20 additional lbs with upgraded controller/battery
• Weight calculation 180+20=200
• Aggressive rider = Heavy tune with low preload
• Relaxed rider = Medium tune with high preload

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.

Which Tune Should You Choose? 🤔

Trail Tune
👉 Best for all-around riding. Sporty, supportive, and versatile. Plush enough for rough terrain, firm enough for g-outs and small jumps.

MX Tune
👉 Motocross focused. Firm suspension built for speed, whoops, and big landings. Maximum control and bottoming resistance at race pace.

SX Tune
👉 Pro-only. The stiffest setup in the lineup, developed with Josh Hill for the biggest hits and hardest landings. If you’re not racing at a pro level, it’ll feel too firm.

⚡ Simple Rule:

• Trail = Versatile everyday shredder

• MX = Track and moto performance

• SX = Beast mode (for pros only)

MX Tune is a motocross specific tune with balance, control, and bottoming resistance for the fastest speeds. It's firm suspension for maximum control and support for huge jumps, whoops and fast cornering. If you select the EBMX or MX spec, you’ll compromise a bit of trail plushness for improved bottoming resistance.

Architecture
Upside down fork

Travel
246 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

Triple clamps
Forged 6061 aluminum, type 3 hard anodized coating

Steer tube 
Seamless 7050 aluminum, type 2 anodized coating

Damping
Symmetrical, adjustable closed cartridge with spring backed IFP

Damper bodies
Seamless 7050 aluminum, type 3 hard anodized coating

Rebound
Dual side high tensile steel spring, adjustable

Adjusters
External compression and rebound adjustment

Seals
NBR 

Guards
High impact PP, 210-degree wraparound