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Topping up my hydraulic brakes without bleeding them
I recently bought a mountain bike with hydraulic brakes.

When the brake fluid gets low, more needs to be added. There are a number of tutorials on Youtube, and other places on the internet. They involve bleeding the brakes.. That is having brake fluid flow through the brakes lines, to remove the air. The process is a bit involved.

I did it an easier way. I put the funnel in the brake lever, and added brake fluid. When I squeezed the brake lever, fluid ran in. When I released the brake lever, bubbles came out. I continued this until there were no more bubbles. The brakes were full. It was a simple process.

Not all bikes are the same as mine. On my bike, the brake hoses run down to the calipers, both front and back. With many bikes, the brake hoses might run down, then up again, then down again. Air will accumulate in the high points. When the hoses run continuously down to the calipers, and continuously up to the levers, the air works its way up. All of the air finishes up in the brake levers. There is no air trapped elsewhere. So it is a simple process to top up the brake levers.

My first caliper failed after 3000 km. I don't expect the other one to last really long. So I don't care about replacing the brake fluid.


As the hydraulic brakes fail, I replace them with cable brakes. Right now, I am running one of each.

Here is a picture of a bike with a similar shape to mine. You can see how the brake hoses run continuously down to the calipers, and air can rise continuously up to the levers, on both front and back. There is no down and up and down again in the brake lines, where air could get trapped.

Because the hoses are thin, the air may take some time to get to the top. But the air eventually all rises to the levers.

When the brake fluid is low, it only needs to be topped up, not bled.


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