Shimano RS805/RS505 Brake Caliper Fitment

The world of cycling is constantly evolving, and with it, the technology that keeps us rolling smoothly and safely. Hydraulic disc brakes have become a staple for many cyclists, offering superior stopping power and modulation in all conditions. For those looking to upgrade or replace their braking system, understanding the intricacies of caliper installation is paramount. This guide will walk you through the process of fitting the popular Shimano BR-RS805 and BR-RS505 hydraulic disc brake calipers, ensuring a professional and effective setup.

Understanding Your Shimano Calipers

The Shimano BR-RS805 and BR-RS505 calipers are part of Shimano's road hydraulic disc brake range. While they share many similarities, minor differences might exist in their specific applications or compatibility with certain levers and rotors. Both systems rely on hydraulic fluid to actuate the pistons that push the brake pads against the rotor. A correct installation is crucial for reliable braking, preventing issues like rubbing, poor performance, or even damage to components.

Pre-Installation Checks: What You'll Need

Before you begin, gather all the necessary tools and components. This ensures a smooth workflow and avoids frustrating interruptions. You will require:

• Your new Shimano BR-RS805 or BR-RS505 caliper.
• New brake pads (compatible with your caliper model).
• Torque wrench with appropriate bits (usually Allen keys).
• Mineral oil (Shimano recommends their own).
• Bleed kit (specific to Shimano hydraulic brakes).
• Allen keys (typically 4mm and 5mm).
• Torque wrench.
• Clean rags.
• Gloves (to keep oil off components and your hands).
• Possibly a brake hose cutter and ferrules/olives.

Step-by-Step Installation Guide

1. Removing the Old Caliper (If Applicable)

If you are replacing an existing caliper, carefully disconnect the brake hose. Be prepared for a small amount of mineral oil to escape; have a rag ready to catch it. Unscrew the mounting bolts that secure the old caliper to the frame or fork. Note the orientation of the caliper and any mounting hardware for reference.

2. Preparing the New Caliper

Your new Shimano caliper will likely come with a bleed spacer, often brightly coloured (like yellow), inserted between the pistons. This spacer is vital for protecting the pistons during transit and should be removed before fitting the pads. It's a good practice to keep this spacer handy until the brake system is fully bled, as it can be useful for testing lever feel.

3. Installing the Brake Pads and Bolts

This is a critical step. The provided diagram indicates that you should install the new brake pads and their retaining bolts. It's important to ensure the pads are correctly oriented. Shimano pads typically have a specific way they slot into the caliper body. Refer to the illustration provided with your new caliper or consult Shimano's technical documentation for precise pad placement. The diagram specifically mentions installing the new brake pads and bolts, and at this point, making sure the retainer is in place. The illustration shows how the pads should be installed. For the BR-RS805/RS505 models, the process remains consistent: insert the pads and then secure them with the provided bolts and retainer.

Important Consideration: When installing new pads, ensure they are clean and free from any grease or oil. Contamination can significantly impair braking performance.

4. Mounting the Caliper to the Frame/Fork

Align the new caliper with the mounting points on your frame or fork. For post-mount calipers, you will typically use specific mounting bolts, often with washers. For flat-mount calipers, the mounting process will differ slightly, often involving adapter plates depending on your frame. Consult your frame manufacturer's specifications if you're unsure about the correct mounting adapter or bolt type.

Torque Specifications: It is crucial to tighten the caliper mounting bolts to the manufacturer's specified torque. Over-tightening can strip threads or damage the frame/fork, while under-tightening can lead to caliper movement and inconsistent braking. For most Shimano calipers, the mounting bolts are typically tightened to around 6-8 Nm, but always verify this with Shimano's official documentation for your specific model.

5. Connecting the Brake Hose

If you've had to disconnect the brake hose from the caliper, you'll need to reconnect it. This involves inserting a new olive and a new sealing bolt into the end of the hose. Ensure the hose is cut cleanly and squarely. Then, thread the sealing bolt through the caliper and into the hose connector. Tighten it securely, but avoid over-tightening, which can damage the hose or the caliper's internal threads. If you are installing a new hose, ensure it is routed correctly and secured along the frame or fork without any kinks.

6. Bleeding the Brakes

This is arguably the most critical step after physical installation. Even if you haven't disconnected the hose, any air introduced during the process or minor impurities can affect performance. Bleeding removes air bubbles and ensures that the hydraulic system is full of fresh mineral oil, providing optimal lever feel and stopping power.

The bleeding process for Shimano hydraulic brakes typically involves:

1. Attaching a bleed cup to the lever's bleed port.
2. Attaching a syringe filled with fresh mineral oil to the caliper's bleed port.
3. Opening the caliper's bleed port screw.
4. Gently pushing oil from the syringe to push air and old oil up into the bleed cup.
5. Closing the caliper's bleed port screw while oil is still flowing.
6. Detaching the syringe.
7. Opening the bleed port screw on the lever while pushing the lever in.
8. Closing the lever's bleed port screw.
9. Removing the bleed cup and installing the blanking plug.

Important Note: Always use Shimano's specific mineral oil. Using other fluids can damage the seals and internal components of your brake system.

7. Final Adjustments and Bedding-In

Once the caliper is mounted and the system is bled, you'll need to make some fine adjustments. Ensure the caliper is centered over the rotor. When the brake lever is pulled, the pads should engage the rotor evenly. If the caliper is off-centre, you can adjust its position by slightly loosening the mounting bolts, squeezing the brake lever firmly, and then re-tightening the mounting bolts while holding the lever. This method often helps centre the caliper automatically.

Bedding-in: New brake pads and rotors need to be 'bedded-in' to achieve optimal performance. This process transfers a thin layer of pad material onto the rotor surface. To do this, perform several moderate-to-hard braking actions from a moderate speed (e.g., 20-30 mph) down to a slower speed, but without coming to a complete stop. Allow the brakes to cool down between braking cycles. Repeat this process 10-20 times. You should notice the braking power increasing as you go through the process.

Troubleshooting Common Issues

Even with careful installation, you might encounter minor issues. Here are a few common problems and their solutions:

Frequently Asked Questions (FAQs)

Q1: Can I use automotive brake fluid instead of Shimano mineral oil?

A1: Absolutely not. Shimano hydraulic brakes use mineral oil. Automotive brake fluids (like DOT fluid) are incompatible and will damage the seals and internal components of your brake system.

Q2: How often should I bleed my hydraulic brakes?

A2: This depends on usage and conditions, but generally, bleeding every 6-12 months is a good practice. If you notice a spongy lever feel or reduced braking performance, it's time to bleed them sooner.

Q3: What torque should I use for the caliper mounting bolts?

A3: Typically, 6-8 Nm, but always refer to Shimano's official documentation for your specific caliper model and your frame manufacturer's recommendations.

Q4: Do I need to replace the brake hose when installing a new caliper?

A4: Not necessarily, unless the old hose is damaged or you are changing the hose length. However, you will need to use a new olive and sealing bolt when reconnecting the hose to the caliper.

Q5: What's the difference between BR-RS805 and BR-RS505?

A5: The BR-RS805 is generally considered a higher-tier component, often paired with Shimano's Ultegra-level groupsets, offering slightly lighter weight and potentially finer finishing. The BR-RS505 is typically found in the 105-level groupsets. Functionally, they offer very similar hydraulic braking performance for their respective categories.

Conclusion

Installing Shimano BR-RS805 and BR-RS505 brake calipers is a manageable task for the home mechanic with the right tools and a methodical approach. Paying close attention to details like pad orientation, torque specifications, and the crucial bleeding process will ensure your new brakes perform reliably and effectively. Remember to always consult the official Shimano service manuals for the most accurate and up-to-date information specific to your components. Enjoy the enhanced stopping power and control that properly installed hydraulic disc brakes provide!