Is you motorbike's braking system feels too spongy?? Is your motorbike's brake level or pedal travel too long? Then its time to bleed the brakes. I've learned about this process in my theory subjects and had a practical experience of this process in my college's Go-Kart racing team by doing it multiple times. Can you able to believe that the whole braking system failed due to the slight deposition of the rotor and the caliper. Will discuss about my whole experience in a separate post and in this article, let's discuss about the brake bleeding process and why its done.
The process of removing the air from the braking line in the hydraulic braking system is known as brake bleeding. Don't worry.. I won't steal your time by taking theory class. Let's see about it shortly and the process of the same. As I said previously, removing the air from the fluid line is what this all about. First of all, we have to think about something. How the atmospheric air enters the braking line though the system is fully sealed. Generally, brake fluid is hygroscopic which means, it absorbs moisture from the atmospheric air.
Water in the braking line lowers the boiling point of the brake fluid which results in the formation of air when the brake fluid is heated. As we all know, brake fluid is incompressible but the air is compressible. When we press or pull the brake lever or pedal at this situation, pedal or lever travels more, compressing the air present inside the fluid line not the brake fluid thereby making the braking action too spongy. If we fails to notice this before, it may lead to something horrible.
So the air should be removed from the braking line soon after noted. All we need is medium or big sized syringe, rubber tubes for some length, waste cloth, ring spanner (size will differ from model to model especially 8, 9 and 10) and a star screwdriver. Firstly, we have to take the cap off the brake reservoir and wipe all the old braking fluid. Make sure that all the old braking fluid from the line and caliper is completely drained out. This can be done by pumping the lever or pedal after loosening the caliper's bleeder nipple.
If you have enough tools, you can remove the banjo bolt from both the caliper and master cylinder and clean them. But you have to be careful with the banjo bolt because tightening it by threading wrongly will damage both the internal & external threads on the caliper and bolt. My suggestion is like after making sure that we have installed correctly by hand tightening it, then we can tight it with the help of wrench or spanner. After completing the whole lot of removing process, its time to bleed the brake.
After closing the bleeder nipple, fill the reservoir with manufacturer's suggested brake oil and pump it. You can able to notice the decrease in oil level by pumping it. Pump it continuously still the pedal or level is loaded. To complete the process, surely you'll need another person. After loading, one person must be ready near the caliper by putting the wrench at the bleeder nipple. After that, you have to pump the lever or pedal about 4 to 5 times and hold it firmly. Then the person near the caliper should open and close the bleeder nipple within a second or otherwise again the air will enter the line through the nipple.
By doing this, oil level in the reservoir will decrease so that you have to make sure that enough amount of oil is present in the reservoir always. If not, again the air will enter the line through that. This process removes all the air present inside the braking line with some amount of brake oil coming with it. You have to be careful on this process and if not, again the air enters the line resulting in the spongy braking feel. Another thing is to protect the exposed painted parts such as fender, fuel tank etc.. because, brake oil affects the paint of the vehicle which results in fading.
You have to repeat this process multiple times to make sure that the air is completely removed off the braking line and you can stop this process after the lever or pedal is completely loaded. Finally we have to check the level of the brake oil in reservoir and have to top it up if necessary. Confirm once again that the bleeder nipple is closed tightly and don't forget to close the reservoir with its cap. There's also a another method which is known as reverse bleeding. This is done by injecting the brake oil in the line via the bleeder nipple directly with the help of syringe & tube and the whole lot of air present inside the air comes out via the reservoir. This process is short & simple and not a time consuming one but you have to close the bleeder nipple as soon as possible after injecting the oil fully.
Related article
- Common problems in a motorbike braking system
The process of removing the air from the braking line in the hydraulic braking system is known as brake bleeding. Don't worry.. I won't steal your time by taking theory class. Let's see about it shortly and the process of the same. As I said previously, removing the air from the fluid line is what this all about. First of all, we have to think about something. How the atmospheric air enters the braking line though the system is fully sealed. Generally, brake fluid is hygroscopic which means, it absorbs moisture from the atmospheric air.
Water in the braking line lowers the boiling point of the brake fluid which results in the formation of air when the brake fluid is heated. As we all know, brake fluid is incompressible but the air is compressible. When we press or pull the brake lever or pedal at this situation, pedal or lever travels more, compressing the air present inside the fluid line not the brake fluid thereby making the braking action too spongy. If we fails to notice this before, it may lead to something horrible.
So the air should be removed from the braking line soon after noted. All we need is medium or big sized syringe, rubber tubes for some length, waste cloth, ring spanner (size will differ from model to model especially 8, 9 and 10) and a star screwdriver. Firstly, we have to take the cap off the brake reservoir and wipe all the old braking fluid. Make sure that all the old braking fluid from the line and caliper is completely drained out. This can be done by pumping the lever or pedal after loosening the caliper's bleeder nipple.
If you have enough tools, you can remove the banjo bolt from both the caliper and master cylinder and clean them. But you have to be careful with the banjo bolt because tightening it by threading wrongly will damage both the internal & external threads on the caliper and bolt. My suggestion is like after making sure that we have installed correctly by hand tightening it, then we can tight it with the help of wrench or spanner. After completing the whole lot of removing process, its time to bleed the brake.
After closing the bleeder nipple, fill the reservoir with manufacturer's suggested brake oil and pump it. You can able to notice the decrease in oil level by pumping it. Pump it continuously still the pedal or level is loaded. To complete the process, surely you'll need another person. After loading, one person must be ready near the caliper by putting the wrench at the bleeder nipple. After that, you have to pump the lever or pedal about 4 to 5 times and hold it firmly. Then the person near the caliper should open and close the bleeder nipple within a second or otherwise again the air will enter the line through the nipple.
By doing this, oil level in the reservoir will decrease so that you have to make sure that enough amount of oil is present in the reservoir always. If not, again the air will enter the line through that. This process removes all the air present inside the braking line with some amount of brake oil coming with it. You have to be careful on this process and if not, again the air enters the line resulting in the spongy braking feel. Another thing is to protect the exposed painted parts such as fender, fuel tank etc.. because, brake oil affects the paint of the vehicle which results in fading.
You have to repeat this process multiple times to make sure that the air is completely removed off the braking line and you can stop this process after the lever or pedal is completely loaded. Finally we have to check the level of the brake oil in reservoir and have to top it up if necessary. Confirm once again that the bleeder nipple is closed tightly and don't forget to close the reservoir with its cap. There's also a another method which is known as reverse bleeding. This is done by injecting the brake oil in the line via the bleeder nipple directly with the help of syringe & tube and the whole lot of air present inside the air comes out via the reservoir. This process is short & simple and not a time consuming one but you have to close the bleeder nipple as soon as possible after injecting the oil fully.
Related article
- Common problems in a motorbike braking system
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