SHIMANO SM-MA-R140-PD BRAKE ADAPTER 140MM REAR POST MOUNT
Low-Profile Precision for Modern Road & Gravel.
The Shimano SM-MA-R140-P/D is a specialized adapter designed for the latest generation of disc-brake road and gravel frames.This adapter allows you to mount a standard Post Mount (PM) caliper onto a frame utilizing the Flat Mount (FM/Direct) standard.Specifically engineered for the rear of the bike, it provides the perfect offset for a 140mm rotor, enabling a sleek, integrated look that aligns with modern aerodynamic and aesthetic standards.
Constructed from high-strength aluminum, this adapter ensures a rigid connection between the frame and the braking system. By maintaining strict alignment tolerances, the SM-MA-R140-P/D eliminates brake rub and ensures consistent pad contact, providing the modulation and reliability required for high-speed road descents and technical gravel sections.
Key Features
Flat-to-Post Conversion: Specifically engineered to mount a 74mm Post Mount caliper onto a modern Flat Mount (Direct) rear frame interface.
140mm Rear Optimized: Precisely spaced for a 140mm disc rotor, offering the most compact and lightweight braking configuration for road and XC use.
Streamlined Profile: Designed to sit as close to the chainstay as possible, improving aerodynamics and reducing the risk of snagging on trail debris.
Rigid Alloy Construction: Forged and machined to provide maximum braking stability, ensuring a crisp lever feel and preventing caliper flex under load.
Corrosion Resistant Finish: Features a durable black anodized coating that protects the adapter from road salt, grime, and moisture.
Complete Hardware Support: Designed to work with standard Shimano mounting bolts, ensuring a secure and vibration-resistant installation.
Technical Specifications
| Feature | Specification |
| Model Number | SM-MA-R140-P/D |
| Mount Type | Flat Mount (Frame) to Post Mount (Caliper) |
| Rotor Size | 140 mm |
| Position | Rear Only |
| Material | Anodized Aluminum |
| Compatibility | Shimano, SRAM, and Magura PM Calipers |
✅ Why This IS For You
Modern Road & Gravel Riders: If you are building up a new Flat Mount frame but want to use your existing high-performance Post Mount hydraulic calipers.
Weight-Conscious Builders: Perfect for those seeking the lightest possible rear brake setup by utilizing the compact 140mm rotor standard.
Clean Aesthetic Seekers: Ideal if you want your brake system to look as integrated and low-profile as possible on a modern carbon or alloy frame.
❌ Why This May NOT be for you
High-Heat/Heavy Loading: A 140mm rotor provides less surface area for cooling; if you are bikepacking with a heavy load or doing alpine descents, a 160mm setup is recommended.
Legacy IS-Mount Frames: This is for Flat Mount frames only. If your frame has the older "sideways" eyelets, you will need an IS-to-Post adapter (like the SM-MA90-R140-P/S.
BFC Pro Tip
The SM-MA-R140-P/D is a precision component that relies on a perfectly flat mounting surface. When installing this on a new frame, ensure the Flat Mount bosses on your chainstay are free of any paint buildup or burrs—this is critical for preventing "brake squeal." Because Flat Mount bolts usually thread up through the frame from the bottom, we always recommend a small dab of blue Loctite and using a torque wrench to meet the manufacturer's specs. A 140mm rear setup is the "pro look," but make sure your brake pads are fresh to get the most out of the smaller rotor's surface area!
