Sirris R38 Rear Shock | E Ride Pro SR

Big moto performance. Bombproof durability.

The Sirris R38 rear shock brings proven, full-size motocross suspension technology to the E Ride Pro SR. It combines internal architecture shared with the larger Sirris R46 platform, a high-flow damping system, and an oversized chassis engineered to handle repeated hard hits, high temperatures, aggressive trail riding, and serious abuse.

Where smaller shocks can begin to fade, leak, or lose consistency under demanding riding, the R38 is designed to keep its damping controlled and predictable. Its pro-level CMX, or Compact Motocross Tune, provides the pressure balance, rapid response, traction, and support normally associated with much larger powersports suspension.

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Spring Rate Options

Sirris offers two spring-rate ranges for the E Ride Pro SR. Select the option using your body weight without riding gear. Sirris has already calculated 15 pounds of riding gear into the listed ranges.

• Medium: 140 to 180 lb rider, 90 N/mm spring
• Heavy: 180 to 220 lb rider, 100 N/mm spring

Technical Specifications

• Architecture: Piggyback shock with steel spring
• Length: 289 mm
• Stroke: 78 mm
• Weight: 3.3 lb / 1.5 kg without spring
• Bottom-out system: MCU bumper
• Top-out system: Rubber bumper
• Seals: HNBR

2SC Compression and Rebound Adjustment

The R38 uses Sirris 2SC, or Two Stage Compression, with independently adjustable high-speed and low-speed compression circuits. This gives riders more control over chassis movement, sharp impacts, jumps, braking bumps, and overall rear-wheel traction.

• Tool-free low-speed compression adjustment, 18 clicks
• High-speed compression adjustment, 24 clicks using a 20 mm hex
• Tool-free rebound adjustment, 24 clicks
• Adjustable spring preload

High-Flow Damping Architecture

The R38 shares the high-flow base-valve cavity architecture used in the larger Sirris R46. Its increased oil flow creates a genuine moto-level damping feel with better control and consistency. Fully tunable compression and rebound circuits help the shock remain cool and predictable during repeated impacts and demanding riding.

This high-flow design improves pressure balance and frequency response, allowing the shock to react quickly to changing terrain without becoming harsh or unsettled. Each R38 is tuned specifically for its intended bike model and is designed to pair with the Sirris F43 CMX fork for balanced suspension performance, dependable traction, and greater confidence at speed.

Reservoir

The reservoir is designed around the large 16 mm shock shaft and its increased oil-displacement requirements. An R46-spec internal floating piston system precisely manages shaft displacement, helping maintain a consistent damping feel through repeated hard hits and high heat loads.

Shock Shaft

The R38 uses the same shaft design as the R46. Its massive 16 mm induction heat-treated hollow steel shaft has a hard chrome finish for extreme structural strength and increased oil flow through the main piston.

• 16 mm outside diameter
• 5.5 mm inside diameter
• Chrome-plated, induction-hardened steel
• Hollow construction for high oil flow

Shock Body

A smaller-diameter body, spring, retainer, and hardware package allow the R38 to fit compact e-moto platforms while retaining the oversized internal flow characteristics responsible for its controlled ride quality.

• Seamless 6061 aluminum construction
• Type III hard-anodized coating
• ACME thread

Main Piston and Piston Band

The 38 mm high-flow main piston uses true powersports architecture. It is slightly smaller than the R46 piston but follows the same design philosophy, providing a wide tuning range and consistent damping performance beyond what is commonly found in this compact shock category.

• CNC-machined 6061 billet aluminum piston
• Type III hard-anodized coating
• Hard piston band

Spring Retainer

• Seamless 6061 aluminum
• Type III hard-anodized coating
• ACME thread
• Manual preload adjustment with locking feature

Body Cap and Lower Eyelet

The upper body cap is engineered for tighter chassis clearance without restricting internal oil flow. A model-specific lower eyelet maintains maximum rebound oil flow to the shaft and metering rod while allowing the R38 to fit smaller e-moto platforms.

• Ultra-durable chrome-plated spherical bearings
• Teflon-lined bearing surfaces

Fitment and Required Parts

• Fits: E Ride Pro SR
• Required linkage: Sirris and Prickly R38-specific linkage, sold separately
• Shock size: 289 x 78 mm
• Rear ride-height change: The required linkage raises the rear of the bike by 25 mm to provide clearance and optimized suspension geometry
• Important: The stock E Ride Pro linkage will not work with the Sirris R38 shock
• Optional front-height correction: A CMX fork drop clamp can be added to raise the front by an equivalent 25 mm
• Recommended fork pairing: Sirris F43 CMX fork

Why Upgrade to the R38?

The R38 stands out because Sirris did not simply scale up a lightweight bicycle shock. Its 16 mm hardened shaft, 38 mm high-flow piston, R46-spec reservoir system, separate high-speed and low-speed compression controls, and model-specific CMX damping tune give the E Ride Pro SR a more planted, controlled feel when the terrain gets fast or rough.

For riders pushing higher speeds, larger jumps, rough trails, or repeated hard impacts, the extra oil flow and heat management help reduce damping fade. The adjustable compression, rebound, and preload settings also allow the suspension to be dialed in for rider weight, terrain, and riding style instead of settling for a one-setting-fits-all shock.

Best Fit for These Riders

• Aggressive E Ride Pro SR riders who need better control through jumps, braking bumps, rocks, and repeated hard hits
• Heavier or faster riders who regularly overwhelm the consistency and heat capacity of smaller stock-style shocks
• Riders building a balanced compact motocross setup with the Sirris F43 CMX fork, R38-specific Prickly linkage, and optional CMX fork drop clamp