Sirris R46 MX Tune Rear Shock | By Sirris Suspension | For Sur-Ron Ultra Bee

Motocross-Tuned Suspension Built for Real Speed

At REV Rides we see a lot of Ultra Bee riders starting to push their bikes into true motocross territory. The Sirris R46 MX Tune Shock was built exactly for that type of riding. This pressure-balanced piggyback shock delivers race-ready control, serious bottom-out resistance, and the type of support needed for jumps, whoops, and fast cornering.

The MX Tune is Sirris’ motocross-specific setup for the Sur-Ron Ultra Bee. Compared to a trail-focused tune, this configuration prioritizes high-speed control and bottoming resistance. The suspension is firmer and more supportive, allowing riders to hit bigger features, land harder, and maintain stability through aggressive terrain.

When paired with a Sirris front fork, this shock completes a balanced suspension system that transforms how the Ultra Bee handles under real riding conditions. The R46 platform was designed specifically for lightweight electric motorcycles where torque delivery and weight distribution demand suspension that reacts quickly and stays consistent.

Why the R46 MX Tune Shock Stands Out

• Large Ø46mm high-flow piston improves damping control and consistency

• Piggyback reservoir design maintains pressure balance and reduces fade

• MX Tune valving built for high-speed motocross riding

• Fully adjustable compression and rebound for precise tuning

• Spring rates matched to rider weight for proper suspension balance

• Type III hard anodized components increase durability and wear resistance

• Induction hardened hollow shaft improves strength while reducing weight

• Fully rebuildable design allows long-term serviceability and custom tuning

MX Tune Performance

The MX Tune is built for riders pushing their Ultra Bee at motocross speeds. This setup prioritizes support and bottom-out resistance while maintaining stability through rough terrain and aggressive riding conditions.

• Maximum bottom-out resistance for big jumps

• Strong support through whoops and fast braking bumps

• Improved corner stability at higher speeds

• Designed for aggressive motocross riding

Technical Specifications

• Architecture: Piggyback reservoir, steel spring

• Shock Length: 320 mm

• Stroke: 85 mm

• Weight: 3.9 lb / 1.76 kg (without spring)

• Piston: Ø46 mm CNC 6061 billet aluminum, Type III hard anodized

• Piston Band: Hard band

• Shaft: Ø16 mm chrome-plated induction hardened hollow shaft

• Shock Body: Seamless 6061 aluminum, Type III hard anodized with ACME thread

• Spring Retainer: 6061 aluminum, Type III hard anodized with locking feature

• Reservoir: Pressurized with floating piston

• Damping: Tunable compression and rebound

• Bottom Out: MCU bumper

• Top Out: Rubber bumper

• Seals: NBR

Rider Weight Options

• Light: 120–160 lb rider weight, 85 N/mm spring

• Medium: 160–200 lb rider weight, 95 N/mm spring

• Heavy: 200–240 lb rider weight, 105 N/mm spring

• X Heavy: 240–280 lb rider weight, 115 N/mm spring

• XX Heavy: 280–320 lb rider weight, 115 N/mm spring

Rider weight ranges are based on body weight without riding gear. Sirris factors approximately 15 lb of riding gear into the recommended ranges. Upgrades such as heavier batteries, controllers, or other components should also be added to rider weight when selecting spring rates.

MX Tune Setup Notes

• Settings are measured in clicks from the fully closed position

• Turn adjusters fully clockwise, then back out to recommended settings

• Riders near weight cutoffs may adjust preload to dial in sag

• Aggressive riders may benefit from moving up one weight class

• Rider preference and terrain may require further tuning adjustments

Example: A 180 lb rider without gear and 20 lb of upgrades calculates total rider weight at 200 lb. An aggressive rider may select the Heavy spring with lower preload, while a more relaxed rider may run the Medium spring with slightly higher preload.

Fitment

• Sur-Ron Ultra Bee

Ideal Riders for This Shock

• Ultra Bee riders focused on motocross riding and big jump capability

• Riders who want maximum rear suspension support and control

• Builders creating a full Sirris suspension setup for track or aggressive riding

Fitment: Sirris R46 E-moto shock w/ MX tune | for Surron Ultra Bee

• Surron Ultra Bee

This product may be compatible with more models than shown above. Please see the product description for full details, or contact us for help with fitment.