How can you tell if your lines are free of air bubbles?
I just change my brake and clutch fluid for the first time. After a happy dance of finally doing it myself someone has now got me all paranoid by saying "if an air bubble crept up in there you wont have any brakes".
I took the bike out right after changing the fluid and the brakes were nice and smooth all the way through. I then practiced some emergency braking and all seems well (slightly better actually).
Can air bubbles show themselves over time or would you be able to notice them right away? Is there any way to ensure the lines are free of air bubbles?
If you've bled until no air bubbles were coming out with fluid you'll most likely be fine. If you've done some emergency braking and everything worked well, I wouldn't worry. Most of that talk is from people who don't trust themselves to work on their own bikes.
You won't have a sudden loss of brake pressure if you still have a few bubbles in the lines. What you will have is "spongy" brakes, by that I mean brakes that aren't solid feeling when you're stopped and you pull hard on the brake lever. If it feels like you're compressing a hard rubber ball when you pull the brake very hard then you likely have some air in the lines. If you're still running the old rubber lines you will feel some give when you really pull hard on the lever, I consider that to be normal and associated with the old rubber lines.
It's tough to verbalize exactly how it should feel. They shouldn't be hard as a brick, but also not so soft that you can't get a good feel for braking power. Now, is that clear as mud? :wink:
My trick to getting bubbles out of the lines is after I filled and bled the system as much as I could, I would keep the reservoir cover off and start flicking the brake/clutch lever repeatedly and watch for bubbles to come out of the hole at the bottom of the reservoir. I would also tap the lines with a big screwdriver handle and caliper (working my way upwards from the caliper to the master cylinder) to knock loose any bubbles in them so they would float upwards to the reservoir. Once the bubbles stop coming up from the reservoir bottom hole, that would be when you will be most sure that you have gotten most or all of the bubbles out of the system. another way people work the bubbles out of the lines is to zip tie the brake lever overnight, so it applies continuous pressure to the brake system. Not sure how that really works, but many have used that method successfully. I guess the pressure will some way make the air bubbles migrate upwards towards the reservoir and eventually upstream of the mater cylinder piston.....
My trick to getting bubbles out of the lines is after I filled and bled the system as much as I could, I would keep the reservoir cover off and start flicking the brake/clutch lever repeatedly and watch for bubbles to come out of the hole at the bottom of the reservoir. I would also tap the lines with a big screwdriver handle and caliper (working my way upwards from the caliper to the master cylinder) to knock loose any bubbles in them so they would float upwards to the reservoir. Once the bubbles stop coming up from the reservoir bottom hole, that would be when you will be most sure that you have gotten most or all of the bubbles out of the system. another way people work the bubbles out of the lines is to zip tie the brake lever overnight, so it applies continuous pressure to the brake system. Not sure how that really works, but many have used that method successfully. I guess the pressure will some way make the air bubbles migrate upwards towards the reservoir and eventually upstream of the mater cylinder piston.....
Beck
95 VFR
avoid keeping the cover open for too long... moisture from the air will get absorbed by the liquid...
My trick to getting bubbles out of the lines is after I filled and bled the system as much as I could, I would keep the reservoir cover off and start flicking the brake/clutch lever repeatedly and watch for bubbles to come out of the hole at the bottom of the reservoir. I would also tap the lines with a big screwdriver handle and caliper (working my way upwards from the caliper to the master cylinder) to knock loose any bubbles in them so they would float upwards to the reservoir. Once the bubbles stop coming up from the reservoir bottom hole, that would be when you will be most sure that you have gotten most or all of the bubbles out of the system. another way people work the bubbles out of the lines is to zip tie the brake lever overnight, so it applies continuous pressure to the brake system. Not sure how that really works, but many have used that method successfully. I guess the pressure will some way make the air bubbles migrate upwards towards the reservoir and eventually upstream of the mater cylinder piston.....
Beck
95 VFR
avoid keeping the cover open for too long... moisture from the air will get absorbed by the liquid...
Erm.....I don't think I ever have the reservoir cover off for more than 20 minutes or so at most to do the "de-bubbling".....
But yes, do not leave it open for hours or overnight.....
My trick to getting bubbles out of the lines is after I filled and bled the system as much as I could, I would keep the reservoir cover off and start flicking the brake/clutch lever repeatedly and watch for bubbles to come out of the hole at the bottom of the reservoir. I would also tap the lines with a big screwdriver handle and caliper (working my way upwards from the caliper to the master cylinder) to knock loose any bubbles in them so they would float upwards to the reservoir. Once the bubbles stop coming up from the reservoir bottom hole, that would be when you will be most sure that you have gotten most or all of the bubbles out of the system. another way people work the bubbles out of the lines is to zip tie the brake lever overnight, so it applies continuous pressure to the brake system. Not sure how that really works, but many have used that method successfully. I guess the pressure will some way make the air bubbles migrate upwards towards the reservoir and eventually upstream of the mater cylinder piston.....
Use clear plastic tubing seated on the bleed nipple, and allow the other end of the tubing to hang down right to the bottom of a glass quart jar while you're bleeding.
Watch the clear tubing for air as you bleed, and do the pump/release/pump release and eventually you will see no air coming through the system.
Keep topping up your master cylinder while you work the brakes.
Sure fire method. Slow and tedious, but you'll get there.
Unless you're repairing part of your break system, you shouldn't need to bleed the brakes. First, if you haven't done this and you have a few extra bucks, repace your bleed nipples (nice phase, eh?) with Speedbleeders. If you're not familiar with them, they are check valves -- that is, one way valves that when open allow you to drain fluid out, but won't allow air to get sucked in. Two, forget about draining and refilling the brake system. Instead, chase the old fluid out with new. As you drain fluid from each caiper, top off the reservoirs with fresh fluid. Don't let them get empty.
Do that, and no air should enter your system in the first place. In theory. In practice -- it works quite well!
This is a big deal with linked brakes, where an entrained air bubble must travel through a couple of hundred miles of tubing before finding an exit. Or so it seems.
Unless you're repairing part of your break system, you shouldn't need to bleed the brakes. First, if you haven't done this and you have a few extra bucks, repace your bleed nipples (nice phase, eh?) with Speedbleeders. If you're not familiar with them, they are check valves -- that is, one way valves that when open allow you to drain fluid out, but won't allow air to get sucked in. Two, forget about draining and refilling the brake system. Instead, chase the old fluid out with new. As you drain fluid from each caiper, top off the reservoirs with fresh fluid. Don't let them get empty.
Do that, and no air should enter your system in the first place. In theory. In practice -- it works quite well!
This is a big deal with linked brakes, where an entrained air bubble must travel through a couple of hundred miles of tubing before finding an exit. Or so it seems.
Aram
I find that in time, the Speedbleeders leak a little bit of air back into the system when you crack them open due to the thread locking agent wearing away. Stahlbus has a much better, albeit slightly more expensive, bleeder valve that does not leak, nor wear your caliper threads over repeated uses.
you can purchase the sealant from speedbleeders. it is in liquid form, if the locking agent gets bad, all you need to do is clean it, apply the sealant, heat treat it and use it once it cools down. Had purchased one small bottle couple of years ago and still using it.
DucatiTerminator
awacs
Unless you're repairing part of your break system, you shouldn't need to bleed the brakes. First, if you haven't done this and you have a few extra bucks, repace your bleed nipples (nice phase, eh?) with Speedbleeders. If you're not familiar with them, they are check valves -- that is, one way valves that when open allow you to drain fluid out, but won't allow air to get sucked in. Two, forget about draining and refilling the brake system. Instead, chase the old fluid out with new. As you drain fluid from each caiper, top off the reservoirs with fresh fluid. Don't let them get empty.
Do that, and no air should enter your system in the first place. In theory. In practice -- it works quite well!
This is a big deal with linked brakes, where an entrained air bubble must travel through a couple of hundred miles of tubing before finding an exit. Or so it seems.
Aram
I find that in time, the Speedbleeders leak a little bit of air back into the system when you crack them open due to the thread locking agent wearing away. Stahlbus has a much better, albeit slightly more expensive, bleeder valve that does not leak, nor wear your caliper threads over repeated uses.
I find that in time, the Speedbleeders leak a little bit of air back into the system when you crack them open due to the thread locking agent wearing away. Stahlbus has a much better, albeit slightly more expensive, bleeder valve that does not leak, nor wear your caliper threads over repeated uses.
I'm not sure I would call $166 'slightly' more expensive. That's a lot of brake fluid I would have to save to make it worthwhile.
I find that in time, the Speedbleeders leak a little bit of air back into the system when you crack them open due to the thread locking agent wearing away. Stahlbus has a much better, albeit slightly more expensive, bleeder valve that does not leak, nor wear your caliper threads over repeated uses.
I'm not sure I would call $166 'slightly' more expensive. That's a lot of brake fluid I would have to save to make it worthwhile.
To be fair, that $166 does include about $36 in aluminum bleeder valve caps look much better than rubber nipple covers but don't serve any other purpose. I typically run Motul RBF600 as my brake fluid which at $20-ish a bottle isn't cheap. I also tend to replace my fluid annually.
Use clear plastic tubing seated on the bleed nipple, and allow the other end of the tubing to hang down right to the bottom of a glass quart jar while you're bleeding.
Watch the clear tubing for air as you bleed, and do the pump/release/pump release and eventually you will see no air coming through the system.
Keep topping up your master cylinder while you work the brakes.
Sure fire method. Slow and tedious, but you'll get there.
When using this method, do you have to tighten the bleeder nipple before each release of the lever?
Use clear plastic tubing seated on the bleed nipple, and allow the other end of the tubing to hang down right to the bottom of a glass quart jar while you're bleeding.
Watch the clear tubing for air as you bleed, and do the pump/release/pump release and eventually you will see no air coming through the system.
Keep topping up your master cylinder while you work the brakes.
Sure fire method. Slow and tedious, but you'll get there.
When using this method, do you have to tighten the bleeder nipple before each release of the lever?
Yes, unless you have a one-way bleeder valve like the Stahlbus or Speedbleeders.