Sirris R38 CMX Rear Shock | Arctic Leopard & Vetra Blazer

Big Moto Performance. Bombproof Durability.

The Sirris R38 CMX Rear Shock brings full-size motocross suspension technology to high-performance e-motos. Designed for the Arctic Leopard XE Pro S, Enduro, XE Pro R, and Vetra Blazer, the R38 takes proven internal architecture from Sirris' larger R46 platform and packages it into a more compact shock built to handle serious e-moto riding.

This is not simply a larger spring or a reworked stock-style shock. Sirris built the R38 around a 38mm high-flow main piston, massive 16mm hollow shaft, R46-spec internal floating piston system, and independently adjustable high-speed and low-speed compression. The goal is better control, heat management, traction, and consistency when you're riding hard enough to make standard suspension start showing its limitations.

The R38 is also tuned specifically for each bike application and designed to pair with the Sirris F43 CMX Fork. Together, the F43 and R38 create a more balanced suspension package for riders looking for predictable front-to-rear performance through rough terrain, jumps, braking bumps, and repeated high-speed impacts.

Important Linkage Requirement

The stock Arctic Leopard linkage WILL NOT work with the Sirris R38.

Fitting a shock this substantial into a compact e-moto chassis required a different approach. Sirris teamed up with TMB to develop an R38-specific linkage for the Arctic Leopard platform. This linkage is sold separately and is required for proper installation on Arctic Leopard models.

Rider Weight & Spring Options

Sirris offers two spring ranges when selecting the R38. Listed weights are the rider's weight without riding gear. Sirris calculates approximately 15 pounds of riding gear into these ranges.

• 140 lbs to 180 lbs: Medium, 110 N/mm spring
• 180 lbs to 220 lbs: Heavy, 120 N/mm spring

Product Specifications

• Architecture: Piggyback, steel spring
• Stroke: 68mm
• Length: 269mm
• Weight: 3.3 lbs / 1.5 kg without spring
• Bottom Out: MCU bumper
• Top Out: Rubber bumper
• Seals: HNBR

2SC Two-Stage Compression Adjustment

The R38 uses Sirris' 2SC Two-Stage Compression system, giving riders independent control over high-speed and low-speed compression. This lets you make more meaningful suspension adjustments based on terrain and riding style instead of relying on a single compression setting to handle everything.

• Low-Speed Compression: Tool-free adjustment, 18 clicks
• High-Speed Compression: 24 clicks, adjusted with a 20mm hex
• Rebound: Tool-free adjustment, 24 clicks
• Spring Preload: Adjustable

CMX High-Flow Damping

The R38 shares the same high-flow base valve cavity architecture found in the larger Sirris R46. The increased oil flow is designed to provide the damping control and consistency riders expect from full-size motorcycle suspension while still fitting the tighter packaging requirements of an e-moto.

Sirris' CMX, or Compact Motocross Tune, uses fully tunable compression and rebound circuits with high-flow internals designed to stay cool and consistent. The system provides improved pressure balance and faster frequency response, helping the shock react to rapid changes in terrain without losing its composure through repeated hits.

Each application is tuned specifically for the bike model. When paired with the Sirris F43 CMX Fork, the R38 is designed to provide balanced front and rear suspension performance with improved traction, control, and confidence at speed.

R46-Spec Reservoir

The reservoir is engineered around the R38's large 16mm shaft and its increased oil displacement requirements. A massive R46-spec internal floating piston system manages shaft displacement while helping maintain consistent damping during repeated hard impacts and high heat loads.

16mm R46 Shaft

The R38 uses the same shaft design as the larger R46. Its 16mm induction heat-treated hollow shaft combines serious structural strength with the ability to move a large volume of oil through the main piston.

• Outer Diameter: 16mm
• Inner Diameter: 5.5mm
• Material: Induction-hardened steel
• Construction: Hollow
• Finish: Hard chrome

Shock Body & Main Piston

Sirris developed a smaller-diameter shock body, spring, retainers, and hardware package for the R38 to fit compact e-moto chassis without giving up the oversized internal flow characteristics responsible for its performance.

The shock body is constructed from seamless 6061 aluminum with a Type 3 hard-anodized coating and ACME threads for durability and precise spring adjustment.

Inside is a 38mm high-flow main piston using true powersports-style architecture. While slightly smaller than the R46 piston, it follows the same design philosophy and provides a broad tuning range with consistent damping under demanding riding conditions.

• Main Piston: 38mm high-flow design
• Piston Material: CNC-machined 6061 billet aluminum
• Piston Finish: Type 3 hard anodized
• Piston Band: Hard band

Spring Retainer, Body Cap & Eyelet

The spring retainer is made from seamless 6061 aluminum with a Type 3 hard-anodized finish, ACME thread, locking feature, and manual adjustment.

A redesigned upper body cap gives the R38 the tighter packaging required for smaller e-moto chassis without sacrificing internal oil-flow performance. It uses ultra-durable chrome-plated, Teflon-lined spherical bearings.

The new lower eyelet is also designed around compact bike fitment while maintaining maximum rebound oil flow to the shaft and metering rod. It also uses ultra-durable chrome-plated, Teflon-lined spherical bearings.

Why Upgrade to the R38?

High-power e-motos can put a surprising amount of heat and force into a rear shock, especially with heavier riders, repeated jumps, fast trail riding, and rough terrain. The R38 addresses that with components normally associated with much larger suspension systems. The 16mm R46 shaft, 38mm high-flow piston, large IFP reservoir, and independent high-speed and low-speed compression circuits give riders more control over how the rear of the bike behaves instead of simply making the suspension stiffer.

That makes the R38 especially useful for riders who want their Arctic Leopard or Vetra Blazer to behave more like a properly set up dirt bike when the terrain gets rough. Better damping control can help the rear tire stay connected through uneven terrain while providing the support needed for harder impacts and aggressive riding.

Fitment

• Arctic Leopard XE Pro S
• Arctic Leopard XE Pro S Enduro
• Arctic Leopard XE Pro R
• Vetra Blazer

Arctic Leopard Fitment Note: The R38-specific TMB linkage is required and sold separately when installing the R38 on compatible Arctic Leopard models. The factory Arctic Leopard linkage is not compatible with the Sirris R38 shock.

Who Is the Sirris R38 For?

• Enduro and technical trail riders looking for better traction and damping control through rocks, roots, braking bumps, and fast-changing terrain.
• Jump and track riders who regularly put the rear suspension through repeated hard impacts and need better heat management and bottom-out control.
• Performance-focused Arctic Leopard and Vetra Blazer riders building a more capable, adjustable suspension package for aggressive riding.