Brake Bleeding and Pressure

[J_C]

Hey guys I've read all the threads on this in recent history, but I wanted to get your take.

After bleeding my brake initially I found that I needed to pump it several times to build a good feel. So I purchased new OEM lines and rebuilt the MC by buying a new OEM piston set. The MC is from an 850 I believe (I have an 1100).

I used a mightyvac to bleed it until I was getting nothing but fluid. I also tried tapping the lines to get air to rise and pusing in on the piston with a screwdriver (Since the lever may not push it ALL the way in). The results are much better, but I still feel like I have a bit too much play. If I squeeze the brake lever twice, on the second one it feels rock solid. It's just on the first where its a little iffy and I'd like it better. Hopefully this rambling info helps describe the situation. Does anyone have any additional ideas? I still have to try the zip tie overnight trick, and if that doesn't work I'm thinking about rotating the calipers to try and get any air stuck there to rise... Anything else?

Thanks folks! She comes home from the old house tomorrow, so it will be good to have her close and be able to try some more techniques out.

[chef1366]

Is the lever returning all the way? Do you have any drag on the rotors?

[mortation]

I replaced both of my calipers and all my lines. I had air out the wazoo. I went to VIP auto and bought a little brake bleeding kit for $5. Followed the instructions and bled both calipers. I did it twice. And the front brakes are rock solid.

Are you making sure during the bleeding process you are not going to low in your reservoir and adding air to the lines? All your nuts in the center are sealed up tight?

Are you closing the bleeder valve before pulling off the tube?

[Jd Powell]

Forget what you know about bleeding brakes the automotive way. Here's an awesome method for bikes.
The brake system is gravity sensitive because of its vertical orientation (as opposed to the mostly horizontal lines in a car.) hence the air wants to go up and the fluid down.
So remove the cap from the master cyl and then remove the cyl from the handlebars. now gently tap the lever just enough to release the air bubbles without pressurizing the line & moving the fluid. Continue to tap the lever as you rotate and tip the master cyl to allow air trapped in bends to escape also flick the brake lines, and turn the bar lock to lock to allow all possible bubbles a verticle path to the master cyl.
This method can also be done with the whole system removed from the bike. Good-Luck.

[J_C]

Are you making sure during the bleeding process you are not going to low in your reservoir and adding air to the lines? All your nuts in the center are sealed up tight?

Are you closing the bleeder valve before pulling off the tube?

Yes to all these questions. I was very careful not to allow any air in from the bottom or the top.

Is the lever returning all the way? Do you have any drag on the rotors?

Yes it is, and no drag




jd, thanks for the suggestion, I may have to try this as well if the other two things i havent tried yet dont fix it. Sounds like you have to be really careful tho!! :shock:

[KEITH KRAUSE]

What has always worked for me...
With glasses on, LOTS of rags protecting paint, etc, and top off fluid close by, remove the union bolt at the MC. Slowly squeeze the lever in fully and hold it. Now positively plug the hole with your thumb before releasing the lever. Now release the lever. Squeeze in again while carefully removing your thumb. Repeat a few times should remove any air trapped in the MC. Just be sure you don't unplug the hole unless the lever is moving in.
I then re-attach the bolt and torque to about 15 ft/lb. Be sure any used crush washers don't leak.
Then bleed at the calipers as usual. I believe your model should be done left caliper first. Any air that entered when you tightened the above bolt/hose should easily go out the caliper without too much pumping. Don't over-torque the bleed nipples. Approx' 3 ft/lb is correct I believe. That's not much. If you ever ding the caliper inside where the bolt tip seals, it's new caliper time.
I run "Speedbleeders" from Russell. I think they're worth the cost of about $17 a pair. They have a one way valve. You just crack them loose about 1/4 turn and pump away 'til the air's out. No need to open/squeeze/close-open...

[Nessism]

In my experience it's perfectly normal for the second pump to be firmer than the first when squeezing the brakes. I think the main cause of softness (other than trapped air) is expansion of the rubber lines. Switching to teflon, with external stainless sheath, really firms things up.