Answered An answer on how to tell if you have air in your brake line with a possible fix

[Pigin]

I often read that people think there is air in their brake system.

The way to check is to repeatedly pull the lever, this is called pumping by most people. If there is a significant difference from the first pulls to the last, in that the lever gets firmer, then there is a good chance you do actually have air in the system.

This is a fix I picked up years ago from my motorcycle days. Repeat the process to get a firm lever. Once it’s firm pull it back to retain the pressure and then hold it back in place with a zip tie or something similar. Leave it overnight and in the morning any air will have made its way to the top of the system and into the reservoir. There is no need to loosen or remove the filler.

Its not guaranteed as this will only work on a fully correctly sealed system.

I would be interested in knowing if this works for you.

Good luck

 

[steve_sordy]

That works, but only on the front brake if you leave your bike on two wheels.
That is because the air bubbles need a continuous upward path to get to the reservoir where a simple front air bleed will do the job. From the front caliper to the reservoir the hose is normally pretty much straight up.

For it to work on the rear brake, the bike needs to be hung up or stood up, such that the whole of the brake hose is as vertical as possible and with no horizontal elements. This can be a faff, but unless you can do it don't bother.

 

[thewrx]

will work in a pinch, and help you bleed better if you have tricky MC's like magura or others.

I guess the big difference between bicycle mc's and and moto mc's is the reservoir being external and thus a bubble could escape to the external reservoir; on a bike its in a sealed compartment so bubbles got nowhere to escape.

 

[steve_sordy]

will work in a pinch, and help you bleed better if you have tricky MC's like magura or others.

I guess the big difference between bicycle mc's and and moto mc's is the reservoir being external and thus a bubble could escape to the external reservoir; on a bike its in a sealed compartment so bubbles got nowhere to escape.

Even if it's a sealed system, bubbles will always float upwards. The "clamp lever and leave overnight" technique has worked for me.

 

[mxh]

As has already been stated, the air needs a continuous upwards route to the reservoir.

What I've done before is to pump the brake then tie it back (as described in the opening post), but then tap / flick the caliper and brake line to dislodge any air inside. Starting at the caliper, work your way up the line, tapping / flicking the line to move any air upwards. Just make sure that you bend the line as you go so that air will keep moving towards the reservoir and can't get trapped along the way.