Brake fluid colour

[cargo]

The process of bleeding involves pushing fluid down the brake lines and through the caliper and out the nipple.

However the timing is important..................each time you release the brake lever the nipple needs to be shut otherwise fluid and air will move back up the line.

A bubble of air could just sit there and never be expelled if you dont get this right.

Squeeze brake lever
open nipple feel pressure drop at lever
close nipple
release lever
squeeze lever
open nipple feel pressure drop
close nipple
release lever
squeeze lever
open nipple feel pressure drop
close nipple
release lever

ad infinatium

[Tirpitz]

Believe me I've done all that, spent 40 minutes doing it exactly per the book and the front was still crap. Several mechanics have told me it's a mug's game on certain bikes, and Kwaks with braided hoses seem to have a particular problem. It doesn't work because you're trying to push air down and physics decrees that it wants to go up. As soon as the fluid flow towards the caliper stops - i.e when the brake lever is fully pulled in and you nip up the bleed valve - the air bubble starts to rise back up to where it was trapped in the first place. As you say - ad infinitum Way to go is to ensure there is no let-up in the fluid flow so the buggers can't escape and the vacuum bleeder does that.

One chaps response to me telling him I was doing it the 'traditional' way was Good luck

Apparently, if you've just got air in the caliper then no probs, it comes out easy. If it's in the line, forget the lever pumping option.

[Tirpitz]

At last, sorted

Vacuum bleeder kit arrived today, hooked up and all done in 10 mins. I drained two MC reservoirs-full per caliper, just to make sure all the air was out of the lines. Anyway, I've mucked about that much with the brakes over the last week, with the reservoir cap off more times than enough, that I wanted to make sure fresh fluid was in the system.

Brakes are now good. They start to apply gradually from almost the first movement of the lever and are rubbing by the time the brake switch clicks. Beyon this they come on for real and then the lever comes up nice and firm, no pumping required.

TBH, I reckon I had got all the air out the other day when I bled at the MC banjo. I tried this technique again this morning and there was nothing there. I'm not absolutely convinced the vacuum bleeder has made much difference to how I had got them the hard way. But what is undoubtedly the case is that the traditional way is a PITA and it takes several days to fully purge the system of air. With a vacuum bleeder you can have the system full and fully bled from dry in less than half an hour. The moral of the story is that if you've got lots of time on your hands an are strapped for cash, do it the traditional way; otherwise get a bleeder kit. The bleeder also makes an annual fluid change a doddle so over time will be worth having.