Dedicated Subsystem WorkbenchPlatform Gen: 2020–2024
2021 Harley Davidson Low Rider S (FXLRS Milwaukee-Eight) Oil Capacities, Coolant & Fluid Specifications
Verified fluid capacities for 2021 Harley Davidson Low Rider S (FXLRS Milwaukee-Eight): engine oil 4.70 L (5.00 US qt), viscosity 20W-50 SYN3 Full Synthetic or H-D 360, coolant , brake fluid, and fork oil levels.
Gen 2020–2024
Factory Platform Compatibility: All workshop fluid capacities, maintenance milestones, torque specifications, and consumables on this specification sheet are factory-identical across model years 2020 through 2024.
Engine
1868cc
Drive
Chain
Cooling
Air/Oil-Cooled
Fluids & Service Capacities
Shop Fluids →Engine Oil (Drain & Filter Change)4.70 L (5.00 US qt)
Engine Oil (Drain Only)4.25 L (4.50 US qt)
Recommended Oil Viscosity20W-50 SYN3 Full Synthetic or H-D 360
Coolant System CapacityN/A
Brake Fluid StandardDOT 4
Drivetrain, Chain & Gearing
Shop Chains & Sprockets →Drive Chain PitchN/A
Chain Link CountN/A
Front Sprocket TeethN/A
Rear Sprocket TeethN/A
Final Drive ConfigurationBelt Drive
Ignition & Electrical Specifications
Shop Plugs & Batteries →OEM Spark Plug Part NumberHarley 6R10 / NGK CPR7EA-9
Electrode Spark Plug Gap0.8 - 0.9 mm (0.031 - 0.035 in)
OEM Battery Reference CodeYTX20HL-BS
Battery Output & Rating12V 18Ah 310 CCA
Spark Plug Inspection Interval10,000 miles (16,000 km)
Wheels, Tires & Inflation Pressures
Shop Tires →Front Tire Dimensions110/90B19
Cold Front Inflation Pressure36 PSI (Cold)
Rear Tire Dimensions180/70B16
Cold Rear Inflation Pressure40 PSI (Cold)
OEM Wheel Rim Widths (F / R)3.50" / 5.50"
Air-Cooled Engine Architecture
Engine Cooling System Hydraulics, Thermostat & Antifreeze Calibration
Air and oil cooling thermal management and fin maintenance for the 2021 Harley Davidson Low Rider S (FXLRS Milwaukee-Eight).
Cooling Configuration
Air/Oil-Cooled Milwaukee-Eight V-Twin
Oil Heat Exchanger: Front Downtube Factory Aluminum Oil Radiator with Thermostat
Max Cylinder Head Temp (Infrared)
215°C
Sustained operation above this threshold breaks down engine oil viscosity and glazes cylinder walls.
Engine Oil Drain Plug Torque
25 N·m
Dry-sump / wet-sump drain bolt with fresh crush washer or O-ring.
Spark Plug Cold Torque
20 N·m
Torque into cold aluminum cylinder head to prevent stripped spark plug threads.
Workshop Cooling Fin Maintenance Protocol
Clean oil cooler radiator matrix mounted between front frame downtubes. Check oil line quick-connect fittings for weeping. Keep cylinder fins free of caked road mud. Never use high-pressure pressure washers on cylinder fins or oil coolers as the high-pressure water stream will fold delicate cooling fins flat and restrict engine thermal dissipation.
BRAKING SYSTEM HYDRAULICS, WEAR LIMITS & CALIPER REBUILD MATRIX
Rotor Discard Limits (Tmin) • Caliper Piston Architecture • Pad Compounds • Hydraulic Bleed Specs
FACTORY CERTIFIED SPECIFICATIONS
Front Rotor Discs
300 mm × 5 mm
Discard Limit: 4.5 mm Tmin
Rear Rotor Disc
292 mm × 5.8 mm
Discard Limit: 5.1 mm Tmin
Caliper Architecture
Brembo 4-Piston Fixed Calipers (Dual Front Discs)
Rear: Brembo 2-Piston Floating Caliper
Hydraulic Fluid Standard
DOT 4 Synthetic Glycol
Dry BP ≥ 260°C • Wet BP ≥ 165°C
Caliper Bolt Torques (NM)
Mount: 38 N·m
Banjo: 27 N·m • Bleed: 8 N·m
Friction Material Lining
Sintered Metallic Heavy-Duty Touring Compound
Discard Pad at ≤ 1 mm
DIGITAL MICROMETER ROTOR WEAR DIAGNOSTIC GAUGE
Measure rotor friction ring with a pointed blade micrometer to verify safe thermal mass and discard limits
Enter Measured Disc Thickness (mm)
mm
Nominal New: 5.00 mm • Stamped Discard: 4.50 mm Tmin
Quick Benchmark Simulation Presets
Enter your micrometer rotor reading above or click a simulation preset to calculate remaining disc service life and discard safety status.
BRAKE PAD FRICTION COMPOUND & METALLURGY MATRIX
Compare OEM sintered metallic, organic carbon-ceramic, and racing compound friction dynamics
Compound Architecture
Double-H (HH) Sintered Metallic Compound
Friction Rating & Thermal Operating Envelope
HH Rated (μ ≥ 0.55 across cold and hot temperature zones)
0°C – 650°C (32°F – 1,200°F) • Exceptional High-Temp Fade Resistance
Lever Modulation & Initial Cold Bite
Sharp, aggressive initial bite with linear lever feel and minimal thermal hysteresis under repeated heavy slowdowns.
Rotor Wear Index & Wet Weather Recovery
Moderate to high rotor abrasive index. Requires hardened stainless steel rotors; not compatible with cast iron discs. • Superior wet recovery. Metallic sintered composition cuts cleanly through surface water film without delaying pad response.
Application & Recommended Riding Profile
Recommended for modern high-performance street motorcycles, spirited canyon riding, two-up touring, and occasional trackdays.
Hydraulic Fluid Bleeding & Caliper Overhaul Protocol
Hygroscopic Moisture Curve
Glycol brake fluid absorbs 2%–3% atmospheric water annually. Over 24 months, boiling point collapses from 260°C (500°F) to below 165°C (329°F), risking sudden vapor-lock brake loss. Flush fluid every 2 years.
Piston Seal Rollback Function
Caliper square-profile rubber seals flex under pressure to retract pistons ~0.15 mm when pressure drops. Hardened or dirty seals prevent rollback, causing continuous pad drag, glazed rotors, and fuel mileage loss.
Bleeder Torque & Sequence
Bleed master cylinder first, then furthest caliper, then nearest caliper. Tighten bleeder nipples to strictly 8 N·m. Over-tightening permanently shears threads in aluminum calipers.
Direct-Fit Braking Components & Hydraulic Fluids
Authentic double-H sintered pads, replacement floating rotors, and high-temp racing brake fluid
1-Click Factory Service KitOEM Spec Fluid Capacities Matched
Workshop Maintenance Kit & Factory Fluids
Authentic factory-grade motor oil, oil filter, and high-temp brake fluid matched precisely to 2021 Harley Davidson Low Rider S (FXLRS Milwaukee-Eight) capacities.
Full Kit Subtotal
$65.34
Matches factory 20W-50 spec (Oil spec: 4.70 L (5.00 US qt))
Item Price
$47.80($11.95 ea)
Premium OEM-spec replacement with 17mm hex nut
Item Price
$11.99
DOT 4 Synthetic Formula
EBC High-Performance DOT 4 Synthetic Brake Fluid
8.8 oz (250 ml) Workshop Bottle
Meets & exceeds factory DOT 4 specifications
Item Price
$5.55
Factory OEM Spark Plug Spec
Harley 6R10 / NGK CPR7EA-9
Gap: 0.8 - 0.9 mm (0.031 - 0.035 in)
Inspection milestone: 10,000 miles (16,000 km). Exact factory part specification.
Authentic OEM Reference
Search OEM Plugs →Explore Other Subsystems for this 2021 Harley Davidson Low Rider S (FXLRS Milwaukee-Eight)
Jump straight into dedicated factory specifications and interactive workshop diagnostic engines.
Subsystem Guide/torques
Fastener Torques
Engine drain plug, axle spindles, caliper mounts, triple clamp pinch bolts & thread lubrication derating guide.
Open Dedicated Workbench →
Subsystem Guide/fuses-relays
Fuses & Relays
Main: 50A Maxi-Fuse • Location: Under rider seat
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Subsystem Guide/compression
Compression & Leakdown
Ratio: 10.2:1 • Std: 180-225 PSI • Limit: 140 PSI
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Subsystem Guide/valves
Valve Clearances
Intake: N/A mm • Exhaust: N/A mm
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Subsystem Guide/fuel-delivery
Fuel Delivery & TB Sync
Idle: N/A • Rail Pressure: N/A • Vacuum: N/A
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Subsystem Guide/electrical
Charging & Battery
Battery: YTX20HL-BS (310 CCA) • Regulated: 14.0 - 14.6 V DC
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Subsystem Guide/tires
Tires & Gearing
Front: 110/90B19 (36 PSI) • Rear: 180/70B16 (42 PSI)
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Subsystem Guide/suspension
Suspension & Sag
Front Travel: 130 mm • Rear Travel: 112 mm
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Subsystem Guide/maintenance
Maintenance Schedule
Oil: Every 5,000 miles (8,000 km) mi • Valves: Every 26,600 mi • Spark Plugs: Every 10,000 miles (16,000 km) mi
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