[Closed] Bleeding brake ideas

You would only get air out of the one which is uppermost though?

I'd be glad to be proven wrong however! 😀

No, not really. You'd bleed between two points (fluid in/air out) but you'd have these points as far apart as possible.

I’m thinking more along the lines of whether the second bleed port is responsible for the systems’ reputation of awkward bleeding and why lever bleeds are ‘a thing’. It seems like somewhere it might be easy to get air trapped.

I’m debating a simple off-bike bleeding rig which has thrown up a secondary question of how much height seperation between calliper and lever is necessary/desirable?  I don’t normally need to bleed too often but when I do I find the bike can be a bit of a pain and was thinking having the system clear of the bike would simplify matters.

I think as much vertical height as possible is probably desirable. But what you really want it to position the bleed screws as high up on the calliper/lever as possible.

An off bike bleeding rig??  Interesting.   If you're pushing the fluid Any way then I doubt the height difference is critical, as long as the lever is above the caliper.

I’m debating a simple off-bike bleeding rig which has thrown up a secondary question of how much height seperation between calliper and lever is necessary/desirable? I don’t normally need to bleed too often but when I do I find the bike can be a bit of a pain and was thinking having the system clear of the bike would simplify matters.

You can use an old pair of handlebars and an old IS mount to position the brake however you want off the bike. It does mean split brake fluid is less of a problem.

You can normally orientate everything on the bike in the workstand, need to slacken the lever on the handlebars to adjust the angle during the bleed, often need to unbolt the rear brake caliper from the frame and let it hang down so there is not a high point that will trap air. I often move the lever up/down/side-side during the bleed to "roll" an air bubble up out the brake lever (it can end up sitting at a high point inside the master cyclinder that is not the bleed screw)

Following the Avid/Sram bleed procedure normally works ok (skip the degassing, more likely to cause more problems than it solves), However you can also screw in a syringe without the plunger to act like as a reservoir and just do a gravity bleed or traditional pull/open/close bleed. Ultimately you need to end up with the system full of fluid with no air, more than one way to do that, whatever is most convenient to you.

You mean number 3 in this diagram?

Those are the fill ports for the reservoir. Normally you'd take off the res cap (as per hopes or motorbike brakes) but the cap is fitted towards the bar, both these ports will go directly to the fluid reservoir. They're not technically bleed ports, more 'fill ports'. A bleed nipple on the lever should be on the master cylinder to allow air in the brake lines and or master cylinder out when it can't get past the cylinder.

Basically, there's no point in bleeding from both sides as they both go to the same area in the reservoir.

Basically, there’s no point in bleeding from both sides as they both go to the same area in the reservoir.

Excellent!  I wasn't sure if there was some fluid path with potential traps involved.  If they literally open into the reservoir then no problem.

Off bike bleed rig - yep, what started me thinking was an old, mostly stripped HT that I occasionally used to stick in the stand and put a particularly problematic brake on without worrying about hose routing etc.  I haven't even reached for an envelope and pen yet but I was thinking along the general lines of broom stick on flat wood frame with an IS>PM bracket by one leg.  Whole thing probably the size of a plastic toy crate and thus not too bad to store and usable on a tabletop.  It's probably an idea that makes no sense to anyone with a dedicated workspace but if you're setting up in a kitchen etc then brake bleeding can be a lot of faff and mess.  Doing it all on a tabletop seems like it might make the mess a lot more manageable...