Properly bleeding and maintaining your Shimano SM-RT70 [paid link] hydraulic disc brakes is essential for ensuring smooth braking performance and maintaining safety while riding. In this guide, we will go over the step-by-step process of bleeding these brakes, followed by a maintenance routine to keep them performing like new.
Tools Required
Before you start the bleeding and maintenance process, gather the following tools:
- Shimano disc brake bleed kit [paid link]
- 5mm hex wrench
- Shimano mineral oil [paid link]
- Syringe and tubing (typically included in the bleed kit [paid link])
- Bleed block or caliper spacer
- Isopropyl alcohol (for cleaning)
- Clean rags or paper towels
- Gloves to protect your hands
- A workstand (optional but helpful)
- A container for used oil
- Torque wrench [paid link]
Understanding Hydraulic Brake Bleeding
Hydraulic disc brakes, such as the Shimano SM-RT70 [paid link], require periodic maintenance to ensure that the hydraulic fluid in the system remains free of air bubbles. Air in the hydraulic lines causes sponginess and can lead to poor braking performance. Bleeding removes this air and ensures that the brake system works efficiently. Over time, the mineral oil [paid link] can also degrade, so replacing it during the bleeding process is highly recommended.
Step-by-Step Guide to Bleeding Shimano SM-RT70 Brakes
1. Prepare Your Bike and Work Area
Begin by securing your bike in a workstand if available. Make sure the brake caliper is easily accessible, as this will be the point where the bleeding process occurs. Gather all the tools and components you need, ensuring that you are working in a clean, well-ventilated space.
2. Remove the Wheel and Install a Bleed Block
For safety, remove the wheel on the brake you intend to bleed. This will allow you to work freely around the brake caliper. Install a bleed block or caliper spacer into the brake caliper to prevent the pistons from pushing out during the bleeding process.
3. Set Up the Syringe and Tubing
Attach the syringe to the bleed port of the brake lever. Ensure the syringe is filled with Shimano mineral oil [paid link], as using the correct type of oil is critical for the hydraulic system’s function. Attach the bleed tube from the syringe to the brake caliper bleed port as well.
4. Open the Bleed Port and Pump the Brake Lever
Use your 5mm hex wrench to open the bleed port on the brake lever. Pump the brake lever gently to force oil through the system, allowing air bubbles to escape. Be mindful of the amount of oil in the syringe and top it up if necessary. The goal is to replace all the old fluid with fresh mineral oil [paid link] and remove any air pockets from the system.
5. Monitor the Brake Fluid Flow
Once the air bubbles stop rising and the fluid starts to flow evenly, close the bleed port on the lever. You should notice that the lever feels firmer and more responsive at this point.
6. Clean and Close the System
After bleeding, it’s important to clean any excess fluid from the caliper and lever using a clean rag and isopropyl alcohol. This will prevent dirt and grime from sticking to the brake components. Tighten the bleed port bolts to the manufacturer’s specified torque setting, and remove the syringe and tubing.
7. Test the Brake Lever and System
Reinstall the wheel and spin it to check for any rubbing or issues with the brake rotor. Pull the brake lever to ensure it feels firm and responsive. If it still feels spongy, repeat the bleeding process until all air is removed.
Maintaining Shimano SM-RT70 Hydraulic Disc Brakes
Regular maintenance of your Shimano SM-RT70 [paid link] disc brakes will prolong their lifespan and ensure consistent performance on every ride. Below are key maintenance tasks to keep your brakes in top condition.
1. Check and Replace Brake Pads
Inspect the brake pads for wear regularly. If the pads have worn down to the indicator line or below, replace them immediately. Shimano SM-RT70 compatible pads should be replaced when they are no longer effective, as worn-out pads significantly decrease braking power.
2. Clean the Rotors
Keep the brake rotors free of contaminants like dirt, oil, or grease. Use a clean rag or paper towel to wipe the rotor surface after each ride. For more thorough cleaning, you can use isopropyl alcohol or a rotor-specific cleaner.
3. Monitor Brake Fluid Levels
Check the brake fluid level [paid link] in the master cylinder and ensure that it remains within the recommended range. If the level [paid link] drops significantly, it could be a sign of a leak or that the brake pads are wearing down and need replacement. Always top up the fluid with the correct Shimano mineral oil [paid link].
4. Inspect the Hydraulic System for Leaks
Periodically inspect the hydraulic system for any signs of leaks, especially around the brake lever, caliper, and hose fittings. If you notice any leaking fluid, immediately stop riding and address the issue by either tightening fittings or replacing damaged parts.
5. Keep the Brake System Free of Debris
Debris can cause uneven brake pad wear and reduce braking performance. Check the area around the brake caliper and rotor for any objects or dirt that could be interfering with the braking system. Clean the area with compressed air if necessary.
6. Bleed the Brakes as Needed
Even with regular maintenance, the hydraulic fluid in your Shimano SM-RT70 brakes can become contaminated over time. Perform a bleed every 6–12 months, or more frequently if you notice spongy brakes or poor performance. This will ensure that the braking system is free from air and the oil is fresh.
Conclusion
By following this guide to bleeding and maintaining your Shimano SM-RT70 hydraulic disc brakes, you can ensure consistent, powerful braking performance on every ride. Regular maintenance, such as checking the brake pads, cleaning the rotors, and monitoring the brake fluid, will help to extend the lifespan of your brakes and improve overall bike safety.