How to Bleed a 1979 Rear Disc Brake Triumph Bonneville for Optimal Performance

Have you ever felt your Triumph Bonneville’s brakes struggling to respond? If you own a 1979 model with rear disc brakes, you might be facing a common issue: air trapped in the brake lines. This can lead to a spongy feel when you press the pedal, making your rides less safe and enjoyable.

Bleeding your rear disc brakes is a simple yet essential maintenance task that can restore your bike’s braking power. In this article, you’ll learn the step-by-step process to get the job done right. With just a few tools and some patience, you’ll have your brakes feeling firm and responsive again, ensuring a smoother ride on your classic Bonneville.

Tools Needed

To effectively bleed the rear disc brakes on a 1979 Triumph Bonneville, gather the following tools:

1. Brake Bleeder Kit

• Choose a kit with a vacuum pump or handheld device for easier operation.

1. Open-End Wrench

• Use a 10mm wrench to open and close the bleeder screw.

1. Clear Tubing

• Find clear tubing that fits snugly over the bleeder screw. This helps you monitor fluid release.

1. Container

• Set up a container to catch used brake fluid. This prevents spills and mess.

1. New Brake Fluid

• Acquire DOT 4 brake fluid to ensure compatibility with your brake system.

1. Rags or Shop Towels

• Keep rags handy to wipe any spilled fluid. Brake fluid can damage paint.

1. Jack and Stands

• Employ a jack and sturdy stands to lift the motorcycle safely. Ensure it’s stable during the process.

1. Safety Glasses

• Wear safety glasses while working with brake fluid. Protect your eyes from splashes.

As you gather these tools, check their condition to ensure everything’s functional and ready for use.

Preparation Steps

Prepare thoroughly before you start bleeding the rear disc brakes on your 1979 Triumph Bonneville. Follow these essential steps to ensure a smooth process.

Safety Precautions

• Wear Safety Glasses: Protect your eyes from any splashes of brake fluid, which can be harmful.
• Work in a Well-Ventilated Area: Avoid inhaling fumes from brake fluid. Open windows or work outdoors when possible.
• Secure the Motorcycle: Use a jack and stands to lift the bike. Ensure it’s stable before beginning the bleeding process.
• Keep a Fire Extinguisher Nearby: Brake fluid is flammable, so have an extinguisher within reach in case of accidents.

Gathering Materials

• Brake Bleeder Kit: This kit usually includes a bleed screw wrench and a catch container.
• 10mm Open-End Wrench: You’ll need this for loosening the bleed screw.
• Clear Tubing: Make sure it’s long enough to fit over the bleed screw and into the container.
• Container for Used Brake Fluid: This will help you manage waste and keep your workspace clean.
• New DOT 4 Brake Fluid: Check your motorcycle’s manual for the correct fluid specifications.
• Rags or Shop Towels: Keep these handy for spills or cleaning up.
• Jack and Stands: Ensure the bike remains in a secure position while you work.
• Cleaning Equipment: Have some surfaces cleaner ready for any spills on the motorcycle.

Check your tools before you start, ensuring everything’s in good working condition. This preparation makes the bleeding process easier and more effective.

Bleeding Process

Bleeding the rear disc brakes on your 1979 Triumph Bonneville involves a few straightforward steps. Follow this guide to ensure you’ve got a solid brake system.

Initial Setup

1. Gather tools: You’ll need a brake bleeder kit, a 10mm open-end wrench, clear tubing, a container for used brake fluid, new DOT 4 brake fluid, rags, a jack, and safety glasses.
2. Prepare the motorcycle: Use the jack to lift the rear of the bike and secure it with stands.
3. Ensure safety: Wear safety glasses and work in a well-ventilated area. Keep a fire extinguisher nearby due to the flammability of brake fluid.

Bleeding the Brake Lines

1. Locate the bleeder valve: It’s usually on the rear brake caliper.
2. Attach tubing: Connect the clear tubing to the bleeder valve and place the other end in the container for used fluid.
3. Open the valve: Use the 10mm wrench to turn the bleeder valve counterclockwise.
4. Pump the brake lever: Squeeze and release the brake lever several times. As you do this, old brake fluid and air will flow through the tubing.
5. Close the valve: After a few pumps, tighten the bleeder valve while the lever is held in. This prevents air from entering the system again.
6. Repeat: Continue this process until clear, bubble-free fluid flows through the tubing.

Checking for Air Bubbles

1. Observe fluid: Look for any air bubbles in the tubing as you bleed the brakes.
2. Monitor the brake feel: After bleeding, pump the brake lever a few times and see if it feels firm. A spongy feel indicates that air might still be present.
3. Conduct a final check: With the bleeder valve closed, repeat the bleeding process if necessary, until there’s consistent clear fluid without bubbles.

After the Procedure

After you’ve bled the rear disc brakes, it’s crucial to ensure everything functions properly. Testing the brakes and cleaning up are essential steps to finalize the procedure.

Testing the Brakes

To test the brakes, sit on your Triumph Bonneville and apply the brake lever gently. The lever should feel firm. If the lever presses all the way to the handlebar, air may still be trapped in the lines. In that case, you must repeat the bleeding process. Take a test ride in a safe area to verify braking performance. Start at low speed and gradually increase it, ensuring strong stopping power without any spongy feel.

Clean-Up

Once the brake testing confirms everything works, focus on cleaning up. Safely dispose of the used brake fluid, as it’s hazardous and can damage paint. Wipe any spilled fluid from the bike’s surfaces with rags or shop towels. Ensure all tools, like the brake bleeder kit and wrench, are collected and stored properly. Finally, inspect the brake fluid reservoir for leaks and top up the fluid if necessary with fresh DOT 4 brake fluid.

Conclusion

Bleeding the rear disc brakes on your 1979 Triumph Bonneville is a rewarding task that can significantly enhance your riding experience. By following the steps outlined in this guide you can restore that firm brake feel and ride with confidence.

Remember to take your time during the process and always prioritize safety. A well-maintained brake system not only boosts performance but also ensures your safety on the road.

Enjoy your rides knowing you’ve taken the necessary steps to keep your classic Bonneville in top shape. Happy riding!

Frequently Asked Questions

What causes spongy brakes on a 1979 Triumph Bonneville?

Spongy brakes are typically caused by air trapped in the brake lines. When air mixes with brake fluid, it reduces braking power and results in a less responsive brake feel.

Why is bleeding the rear disc brakes important?

Bleeding the rear disc brakes removes air from the brake lines, restoring optimal braking performance. This simple maintenance task ensures safety and enhances the overall riding experience.

What tools do I need to bleed the brakes?

You will need a brake bleeder kit, a 10mm open-end wrench, clear tubing, a container for used brake fluid, new DOT 4 brake fluid, rags or towels, a jack and stands, and safety glasses.

What safety precautions should I take when bleeding brakes?

Always wear safety glasses, work in a well-ventilated area, and secure the motorcycle with a jack and stands. Keep a fire extinguisher nearby due to the flammability of brake fluid.

How do I bleed the rear disc brakes?

Locate the bleeder valve on the rear brake caliper, attach tubing, and place the other end in a container. Open the valve, pump the brake lever to expel old fluid and air, then close the valve. Repeat until clear fluid flows through the tubing.

How can I test if my brakes are working properly?

After bleeding the brakes, gently apply the brake lever while seated on the motorcycle. A firm lever indicates successful bleeding, while a lever that presses to the handlebar suggests air may still be trapped.

What should I do after bleeding the brakes?

After bleeding, dispose of used brake fluid safely, wipe any spills, and store tools properly. Check the brake fluid reservoir for leaks and top up with fresh DOT 4 brake fluid if needed.