Product Description
Brembo RCS Radial Brake Master Cylinder for Harley-Davidson
Upgrade your Harley-Davidson's braking system with the Brembo RCS Radial Brake Master Cylinder. Developed using technology from Brembo's MotoGP and World Superbike racing programs, the RCS delivers precise hydraulic control, adjustable lever response, and premium performance for custom motorcycle braking applications.
Featuring Brembo's patented Ratio Click System (RCS), this radial brake master cylinder allows riders to select between two different lever ratios to customize braking feel. Choose a more progressive response for precise modulation or a more immediate response for a firmer, direct feel.
Available in 15mm and 19mm piston configurations for properly matched single- and dual-disc brake systems, these master cylinders feature forged aluminum construction, a hard-anodized finish, and a 1-inch handlebar clamp designed for custom motorcycles and Harley-Davidson applications.
Completing a Brembo brake upgrade? Explore our Brembo brake calipers, master cylinders, and performance components to help build a complete braking system.
Fitment
Designed for custom Harley-Davidson and motorcycle applications using 1-inch (25.4mm) handlebars and compatible hydraulic front brake systems.
Two master cylinder configurations are available:
- Single Caliper - 15mm (110.A897.30): Intended for compatible single-disc front brake systems using one fixed four-piston caliper.
- Dual Caliper - 19mm (110.A897.10): Intended for compatible dual-disc front brake systems using fixed four-piston calipers.
These are universal performance components and are not direct bolt-on replacements for every Harley-Davidson model. Master cylinder sizing must be matched to the specific brake calipers, piston area, and hydraulic system.
Before installation, verify handlebar clearance, brake line connections, brake light switch compatibility, reservoir mounting, and ABS system requirements.
Features
- Premium Brembo RCS radial front brake master cylinder
- Patented Ratio Click System provides adjustable 18mm and 20mm lever ratios
- 18mm setting delivers a more progressive braking response
- 20mm setting delivers a firmer, more immediate braking response
- Forged aluminum master cylinder body
- Hard-anodized finish for durability
- Precision internal hydraulic components inspired by Brembo racing technology
- Adjustable brake lever reach for personalized rider comfort
- Folding brake lever design
- Brake light microswitch for compatible applications
- 1-inch handlebar mounting configuration
- Available in 15mm single-disc and 19mm dual-disc versions
- Optional 45ml brake fluid reservoir kit available
- Designed for premium custom motorcycle braking systems
Specifications
- Manufacturer: Brembo
- Series: RCS (Ratio Click System)
- Application: Front Brake Master Cylinder
- Construction: Forged Aluminum
- Finish: Hard Anodized
- Single Caliper MPN: 110.A897.30
- Dual Caliper MPN: 110.A897.10
- Piston Diameter: 15mm or 19mm depending on selected configuration
- Adjustable Lever Ratio: 18mm / 20mm
- Handlebar Diameter: 1 inch (25.4mm)
- Approximate Weight: 350g
- Brake Fluid: DOT 4
- Brake Line Connection: M10x1.0
- Reservoir: Remote brake fluid reservoir required
- Optional Accessory: 45ml Reservoir Kit
How Does the Brembo RCS Adjustment Work?
The Brembo Ratio Click System allows riders to change the mechanical leverage of the brake master cylinder without replacing components.
The system provides two adjustable settings:
- 18mm Lever Ratio: Provides greater mechanical leverage and a more progressive braking feel. This setting allows finer brake modulation with increased lever travel.
- 20mm Lever Ratio: Provides a more direct braking feel with shorter lever travel. This setting is suited to riders who prefer a firmer, more immediate response.
Changing the lever ratio adjusts mechanical leverage and lever response. It does not change the master cylinder's piston diameter.
Choosing Between the 15mm and 19mm Brembo RCS
Selecting the correct master cylinder piston diameter is essential for proper brake performance.
Brembo 15 RCS - Single Caliper Applications
The 15mm version is designed for properly matched single-disc systems using one fixed four-piston caliper. It is intended for custom motorcycles requiring a smaller master cylinder bore.
Brembo 19 RCS - Dual Caliper Applications
The 19mm version is designed for properly matched dual-disc systems using fixed four-piston calipers. It is commonly considered for performance-oriented dual-caliper brake conversions.
Important: The number of calipers alone does not guarantee compatibility. Master cylinder bore must be selected based on caliper piston area, required hydraulic displacement, lever characteristics, and the complete braking system.
Complete Your Brembo Brake Upgrade
A high-performance master cylinder is only one component of a complete braking system. Depending on your motorcycle and existing brake configuration, additional parts may be required.
Recommended Brake Components
- 45ml Brake Fluid Reservoir Kit: Add the optional 45ml reservoir kit directly from the product options above. A properly sized and mounted remote reservoir is required for installation.
- Brembo M4 Black Radial Brake Calipers - Premium monoblock aluminum calipers with four 34mm pistons and 108mm radial mounting centers. Available individually or as a complete left and right set. Verify hydraulic compatibility with the selected RCS master cylinder before ordering.
- Brembo GP4-RX Nickel Plated Radial Calipers - High-performance CNC-machined billet aluminum calipers featuring four 32mm pistons and premium nickel-plated construction. Master cylinder matching must be verified for the specific brake configuration.
- Harley-Davidson Brake Lines & Hoses - Explore replacement and performance brake lines for custom applications. Confirm brake line length, routing, fitting angles, and connection compatibility.
What Else Is Needed for Installation?
Installation requirements vary depending on the motorcycle and existing brake setup. Additional components may include:
- Compatible remote brake fluid reservoir and mounting hardware
- Reservoir hose and required fittings
- Compatible brake lines and banjo fittings
- Correct sealing washers
- Brake light switch wiring or adapters
- Application-specific installation hardware
The master cylinder uses an M10x1.0 brake line connection. Verify the correct banjo bolt, fitting configuration, and sealing hardware before installation.
Brake Fluid Warning: These Brembo RCS master cylinders specify DOT 4 brake fluid. DOT 4 must not be mixed with silicone-based DOT 5 fluid. Motorcycles originally equipped with DOT 5 require verification of all brake system components before conversion.
For ABS-equipped motorcycles, compatibility must be confirmed before replacing the factory master cylinder. Installation should be performed by a qualified motorcycle technician familiar with hydraulic brake systems.
Frequently Asked Questions
What is the difference between the Brembo 15 RCS and 19 RCS?
The primary difference is piston diameter. The 15 RCS features a 15mm piston intended for compatible single-caliper systems, while the 19 RCS uses a 19mm piston intended for compatible dual-caliper systems. Exact hydraulic compatibility must be confirmed before ordering.
What does the 18/20 adjustment do?
The Ratio Click System changes the brake lever's mechanical leverage. The 18mm setting provides a more progressive response with increased lever travel, while the 20mm setting provides a firmer, more direct response.
Will the Brembo RCS master cylinder fit my Harley-Davidson?
These master cylinders are designed for custom applications using 1-inch handlebars. Proper fitment also depends on brake system configuration, handlebar controls, brake light switching, ABS compatibility, and hydraulic requirements.
Does the Brembo RCS master cylinder include a reservoir?
A remote brake fluid reservoir is required. Get Lowered Cycles offers an optional 45ml reservoir kit that can be selected when ordering this product.
Can I use the Brembo RCS with Brembo M4 calipers?
A Brembo RCS master cylinder may be suitable for an appropriately matched M4 braking system. The correct piston diameter and hydraulic configuration must be verified based on the number of calipers and their total piston area.
Is the Brembo RCS compatible with Harley-Davidson ABS?
ABS compatibility is application-specific and cannot be assumed. The motorcycle's ABS module, hydraulic requirements, brake light controls, and manufacturer specifications must be reviewed before installation.
Shop Brembo Performance Brakes at Get Lowered Cycles
Browse our complete collection of Brembo brake calipers, master cylinders, and performance braking components for custom Harley-Davidson motorcycles.
Need help choosing the right Brembo master cylinder? Contact Get Lowered Cycles at [email protected] with your motorcycle year, model, existing calipers, and brake configuration. Our team can help you identify the components needed for your custom brake upgrade.
| Single | 110.A897.30 |
| Dual | 110.A897.10 |