Bleeding Brakes
- Thread starter tribonnie
- Start date
Peter T.
Junior member
- Location
- Zurich, Switzerland
Hi Richard, I have mounted Stahlbus bleeding valves. Makes bleeding much easier.
Rob
Hero member
- Location
- Midlands, UK
On the bike for front brakes.
Gravity will help, but two items that can trap air are the master cylinder which typically has the brake line banjo as its highest point. This is not helpful! Also the brake splitter being horizontal can again trap air. Unbolting both items and tapping them helps overcome the issue.
A quick way to chase air out of the system is to operate the m/c lever with only a very small movement. Air will bubble up through the reservoir. This avoids the need for full stroke pumps to chase the air down to the calipers.
Gravity will help, but two items that can trap air are the master cylinder which typically has the brake line banjo as its highest point. This is not helpful! Also the brake splitter being horizontal can again trap air. Unbolting both items and tapping them helps overcome the issue.
A quick way to chase air out of the system is to operate the m/c lever with only a very small movement. Air will bubble up through the reservoir. This avoids the need for full stroke pumps to chase the air down to the calipers.
Tippie
Hero member
- Location
- Dr?bak, Norway
I always let capillary effect do almost all the work. With a full reservoir I open up all the bleed nipples (clear hoses into containers) in situ on the bike, and if the m/c doesn't immediately start to empty I give it a few slow pumps to get it to start. When fluid is flowing through all the nipples I close them off one at a time and do the rocking thing with the M/C. Then I check each calliper the usual way opening and closing the bleed nipple with pressure. I has worked for me every time.
Stoutgoose
Junior member
- Location
- UK
I use a large syringe (150ml) you can get them from ebay cheaply, and attach to the bleed nipple and open it, then use a combination of vacuum and brake pedal/lever to push and pull fluid through.
Laverdalothar
Hero member
- Location
- Germany
I bleed them until finally the pistons start moving. Once the do that, I continue pumping until the brake-pads do contact the disc. Then I slowly us the pistons back so that the fluid gets pushed back upwards. This typically removes 90% of the air. After that, I do like Rob described: very low movement of the lever, just so that the master piston starts moving a bit. you will see bubbles coming out of the hole in the reservoir. If that happens, you are on the right way and soon will have a great brake... And leave it over night...
Legs
Hero member
- Location
- Adelaide Hills
As you have replaced the seals, I suspect you may still have air trapped behind the pistons. Might be worth removing the calipers and positioning them so that any air can make it's way up the hoses.
piranha-bro2
Hero member
- Location
- Melbourne
Lothar's suggestion of allowing the pistons to push inward and then using a wedge to force them back into the calipers gets rid of trapped air, not only at the pistons but in areas where bubbles may be lurking upstream.
I recently bled my rear brake and absolutely nothing I did would allow fluid to enter the cavity between primary and secondary seals - the reservoir fluid lever refused to budge no matter where I had the master or caliper (high, low, on the bench, on the bike).
I ended up forcing fluid into the master cyl with a syringe, filled above the piston via the banjo bolt hole and finally I started to get air and fluid moving through the long line to the rear caliper. Gave me no end of grief - to the point that I was convinced the m/cyl was faulty.
Brembo Yamaha R6 master, Ducati Monster Brembo caliper (same as a Zane).
breganzane
Hero member
- Location
- NSW Australia
For the fronts I always find that removing the mc, angling the banjo down and using tiny movement of the lever to vent the air (much as per Rob said above) does the trick. Various tapping of the lines etc to dislodge bubbles might help but the main culprit is usually at the banjo of the MC.
For the rear brake, it always has to be removed from the bike complete and reoriented to get the air out in my experience. It's a pain but in reality the only way due to the high points in the system and the placement of the bleed nipple at the bottom of the caliper when mounted.
A vacuum and/or pressure bleeder can presumably do both in situ and perhaps more quickly but I've never felt the need. Once they're bled the first time, I try to do a yearly flush of fresh fluid through each entire system and if you do that correctly you never get any air in there again so the requirement for a vacuum bleeder is pretty rare.
For the rear brake, it always has to be removed from the bike complete and reoriented to get the air out in my experience. It's a pain but in reality the only way due to the high points in the system and the placement of the bleed nipple at the bottom of the caliper when mounted.
A vacuum and/or pressure bleeder can presumably do both in situ and perhaps more quickly but I've never felt the need. Once they're bled the first time, I try to do a yearly flush of fresh fluid through each entire system and if you do that correctly you never get any air in there again so the requirement for a vacuum bleeder is pretty rare.
Legs
Hero member
- Location
- Adelaide Hills
On the way home from work there was a steep hill about a kilometre long that I had to go down, at the bottom my brakes would fade, the problem remained no matter how many times a bled the brakes using the normal method (squeeze/bleed/shut/release lever).
On close inspection of the calipers I realised that the hose inlet is adjacent to the bleed nipple, meaning that the fresh fluid was going into the caliper and straight out the bleed nipple without circulating within the caliper.
I removed a caliper, one at a time at a time, from the forks and pumped the lever to force the pads towards each other, then tied the lever against the bars to shut off the return hole in the m/c.
I then opened the bleed nipple and pushed the pads apart using a small tyre lever, forcing the fluid behind the pistons out, the colour of the fluid coming up the clear tube from the nipple was black. Did this three or four times on each caliper and the result was fade-free braking.
Anyhow, that's how I solved the problems but as they say, there are many ways to skin a cat.
On close inspection of the calipers I realised that the hose inlet is adjacent to the bleed nipple, meaning that the fresh fluid was going into the caliper and straight out the bleed nipple without circulating within the caliper.
I removed a caliper, one at a time at a time, from the forks and pumped the lever to force the pads towards each other, then tied the lever against the bars to shut off the return hole in the m/c.
I then opened the bleed nipple and pushed the pads apart using a small tyre lever, forcing the fluid behind the pistons out, the colour of the fluid coming up the clear tube from the nipple was black. Did this three or four times on each caliper and the result was fade-free braking.
Anyhow, that's how I solved the problems but as they say, there are many ways to skin a cat.
Andy
Hero member
- Location
- Auckland, roughly
Yep, there’s a lot of muck that stays in the slave if you don’t manipulate the piston.
Dellortoman
Hero member
- Location
- Tasmania, Australia
I just suck a heap of fluid through with a vacuum bleeder. Only takes a few minutes to do each bleed nipple.
Air bubbles in the lines tend to rise to the top. Since you're pulling the fluid downwards from the M/C to the caliper, you need the fluid to flow faster than the rate of ascent of any bubbles. To do that you need a good seal at the nipple and around its threads. I always remove the nipples completely, wrap a few turns of teflon tape around the threads, then put 'em back in before doing the vacuum bleed thing. If there's too much air getting sucked in around the nipple threads, you may not get enough fluid flow to scavenge all the bubbles out.
On rare occasions (mainly on linked brakes with plumbing going all over the bike) I've had to crack a banjo somewhere to bleed a high point.
Air bubbles in the lines tend to rise to the top. Since you're pulling the fluid downwards from the M/C to the caliper, you need the fluid to flow faster than the rate of ascent of any bubbles. To do that you need a good seal at the nipple and around its threads. I always remove the nipples completely, wrap a few turns of teflon tape around the threads, then put 'em back in before doing the vacuum bleed thing. If there's too much air getting sucked in around the nipple threads, you may not get enough fluid flow to scavenge all the bubbles out.
On rare occasions (mainly on linked brakes with plumbing going all over the bike) I've had to crack a banjo somewhere to bleed a high point.
MarnixSFC
Hero member
Spot on Steve, as usual. Only can add, that after the first ride, it is useful to again remove the master cylinder, because there will always be some trapped bubbles waiting to be released.
Marnix
Wowshie
New member
- Location
- Perth Western Australia
I tried this on my front brake a few nights ago, not expecting it to work as it seemed too easy. Released cable tie next morning... perfect.
Laverdalothar
Hero member
- Location
- Germany
If you renew the caliper seals anyway and have the pistons popped out, cleaned everything and are ready to start assembling, I found it to be not wise to push the piston completely in. Instead, I put fluid already into the caliper and push the piston just a bit in so that the new seals would hold the fluid still. I trie to fill them as much as possible. Then I go to the bike, mount the hoses, then the calipers to the bike, the hoses to the master and press the pistons in, making sure the hose connection is the highest point. This pushes so much fluid up the lines that almost no air is in the system anymore. I repeat pumping out the pistons a bit, wait for some time, then pushing them in again. You have a 98% bleaded system now. For the rest, I do what Steve descriped: gently pulling the lever just some milimeters so that the piston in the master juuuuust moves. you'll see little bubbles coming up - stop there, release and go back to that point until no bubbles come up anymore. Job done.
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CLEMTOG
Hero member
I always make a right bleeding mess all over the bike lift and floor. Just hate the stinking feel and texture of the stuff, much prefer it the boys do it for me, but remember, any spillage, with most brake fluids it is washed, neutralised and dispersed with plain old water use lots of it
CLEM
CLEM