Troubleshooting Hydraulic Disc Brakes
Hydraulic disc brakes are one of the greatest innovations the bike world has seen! They are reliable, powerful, and can be found on a wide range of bikes! These little gems are what makes the bike world what it is today. However, hydraulic brakes have seen their fair share of issues, which are easy to come by when not being careful. Groaning, squeaking, failure to perform, etc. If they’re not properly maintained, they can be one of the most frustrating components on a bike! In the following, we will look at some of the most common issues with brakes, and how you can overcome these issues, and get back to doing what you love!
Perhaps the most common issue with hydraulic brakes is noise! Generally noise can be caused by one of three things. Worn parts, a misaligned calliper, or contamination of the rotors or pads (most common),
Brakes are worked by 2 pads contacting a fast moving, generally metal surface. This is a lot of pressure on the braking surfaces, and parts will wear over time. Its a good practice to keep an eye on your brake pads, and rotors, to know when to replace them. When a brake pad looks like its almost level with the metal back plate of the pad, it means its almost completely worn, and should be replaced. Likewise, if the rotor looks bent, or becomes concaved on the braking surface, it means it should be replaced (as seen in the image).
A misaligned calliper is a very common cause of a light squeal when the bike is rolling slowly. This can be diagnosed by lifting the wheel off the ground and spinning the wheel. If a rubbing noise occurs, then the calliper will need re-centring. To do so, put your bike in a work stand, and loosen off both mounting bolts. Pump the brake lever a few times, then loosely fasten the bolts while holding down the lever. Spin the wheel, while listening for any noise. If rubbing persists, loosen one bolt and move the calliper manually until noise decreases. Tighten and repeat to the opposite bolt. Continue this process until the wheel rolls silently, then fasten bolts down.
If rubbing still persists, watch the rotor roll through the calliper, looking for any sidewards movement. If the rotor is bent, the noise may not be able to be silenced. Consider replacing rotor, or having it straightened.
When owning a bike with any form of brakes, its always important to keep the pads and braking surface completely free of any oils. The oils in your fingers can be enough to cause contamination to occur on the braking surfaces. Other common contaminants can include WD-40, degreasers, chain lube, grease, or braking fluid (generally found when bleeding brakes). Once an oil such as these have come into contact with the pads or rotor, the pads become what we call contaminated. However, do not fret! With the right gear, we can generally save the brakes.
Cleaning Your Brakes
To thoroughly clean your brakes, remove the wheel. Now take a clean cloth, and wipe over the rotor braking surface. Keep going over, and checking the cloth for dirt and oils. Once dirty, use another section of the cloth to continue wiping. Repeat this until no dirt is seen on the cloth. Now take some rubbing alcohol, or isopropyl alcohol, and wipe over the rotors. This will remove any final contaminants from the rotor.
Next, remove your brake pads. Set a cloth on a flat surface, and begin rubbing the pads clean on the cloth. Repeat with both pads until mostly clean. Now take a gridded sand paper (grouting sand paper works best), and set it on the cloth. Begin rubbing the pads on the sanding paper with reasonable force. By rubbing the pads in a figure 8, you will prevent uneven wear of the pads. Don’t rub for too long, as you may wear through more of the pad than you need to. Once clean, wipe off once more, and replace into the calliper.
Your pads and disc should be completely clean! If your brakes persist to squeal, the parts may need replacing, as sometimes they have had oil on them too long. The contaminants can bed themselves into the grooves and any imperfections in the components. Other methods of cleaning can involve burning the rotors and pads, to burn out the oils. however, this method is not recommended and can be more harmful than helpful!
Brakes Don’t Lock Up
Brakes that don’t lock on can be one of the most frustrating things about disc brakes. If something isn’t tuned, bled, or maintained correctly, it can lead to a poorly performing brake system. Some of the most common causes for brakes not being able to lock up are;
Contamination of the brakes means an oil, or lubricant may have entered the brake pads or brake rotor. This can be fixed most of the time. (See ‘contamination’ and ‘cleaning your brakes’ to learn how to troubleshoot this problem)
Poorly Bled Brakes
If your brakes feel spongy, inconsistent, or haven’t been bled in a while, you should consider this! As fluid ages, it can absorb moisture through the brake lines, through seals, and other openings in the braking system. This causes the fluid to become thicker, and less reactive to braking. Giving the system a bleed will refresh the fluid, remove any blockages, and any air from the lines. By refreshing the fluid, the brakes will fill firm, consistent, and hopefully lock up the brakes!
With Shimano brakes, insert the funnel into the lever (after a bleed), and fill it a third full with new brake fluid. Keep pumping the lever, and look for any black or old fluid working its way out, into the funnel. This black stuff can sometimes remain in the system after one bleed. By pumping it out, you replace it with fresh fluid. Seal the plunger, remove the funnel, the drip a little fluid into the hole, to ensure the system is absolutely full!
Like anything on a bike, if its worn, it won’t perform how it should. Check the pads still have a decent amount of life in them, to ensure they aren’t the problem. If they are, replace them. Likewise with the brake rotors. (read the ‘Worn Parts’ section above).
Other Braking Issues
There are stacks more issues people have with their brakes.
Avid Brakes Wont Bleed
If Avid brakes aren’t bleeding, first check that your contact adjuster knob (if applicable) is rotated in the opposite direction of the arrow. Sometimes, the little Allen screw located on the inside of the lever, needs to be screwed counter-clockwise, in order to bring the lever in, This can also allow the fluid to flow through much easier.
If they still don’t bleed, it could be a broken seal, or old component. Remove the hose from the calliper, and the lever. Attach the 2 syringes, full with air, to each end. Begin pushing each, one at a time. See if air will pass through each of them. If id doesn’t pass through one, then consider replacing that piece (generally the lever). If it does pass through both, try pumping an air compressor through the hose, to remove any blockages. Now reinstall, and bleed again.
Squishy Noise at the Lever
Sometimes, especially with Avid, there can come a squeak, or squishing noise at the lever, when compressed. Depending wether its a seal, or a rubbing sound, it can be fixed. If its more of a rubbing sound, try spraying a little WD-40 into the lever joints, then wiping off. Work the lever to disperse the WD-40 into the lever. This should silence the squeak. If however, it’s a seal, this can’t easily be replaced. Generally this can indicated a seal is either worn, or out of proper position. Consider replacing.
GMBN have a great video on improving braking performance.
For information on bleeding Avid and Sram brakes, click here for a full, professional tutorial!
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