Confessions from the fuckwits

k3n!f

leaking out the other end
I'm relatively new to brake bleeding, but heard about the gravity bleed technique for Shimano brakes and thought I would give it a go with my brand new brakes. What a farking disaster. After completing the gravity bleed technique I was left with levers that pulled back to the bar and what I can only presume was a 50:50 mix of oil and air in the lines based on how many bubbles were coming out of the lever at the top end.

I'm now in a sunk cost scenario, where I have spent so much time doing the lever mini bleed technique trying to get the bubbles out of the system from the top that rebleeding the system would be admitting defeat and unacceptable for my delicate ego.

Retrospectively I'm thinking a gravity bleed is a great idea to flush out old fluid, but that a syringe bleed from the bottom makes more sense for a brand new set of brakes with no oil in the system. It seems like the gravity bleed technique is like trying to fill a bottle of water from the top and expect the extra air to somehow go out the bottom of the bottle, when filling from the bottom would allow the extra air to float to the top as nature and physics intended.

Am I a total numpty here?
 

Oddjob

Merry fucking Xmas to you assholes
I'm relatively new to brake bleeding, but heard about the gravity bleed technique for Shimano brakes and thought I would give it a go with my brand new brakes. What a farking disaster. After completing the gravity bleed technique I was left with levers that pulled back to the bar and what I can only presume was a 50:50 mix of oil and air in the lines based on how many bubbles were coming out of the lever at the top end.

I'm now in a sunk cost scenario, where I have spent so much time doing the lever mini bleed technique trying to get the bubbles out of the system from the top that rebleeding the system would be admitting defeat and unacceptable for my delicate ego.

Retrospectively I'm thinking a gravity bleed is a great idea to flush out old fluid, but that a syringe bleed from the bottom makes more sense for a brand new set of brakes with no oil in the system. It seems like the gravity bleed technique is like trying to fill a bottle of water from the top and expect the extra air to somehow go out the bottom of the bottle, when filling from the bottom would allow the extra air to float to the top as nature and physics intended.

Am I a total numpty here?
No idea if you are a numpty.

I've found the two syringe method works best.

Attach syringes to both ends with appropriate connectors. Make sure there is 50ml fluid in caliper syringe. Pump from caliper to lever until you see fresh fluid coming through. Discard old fluid. Reattach lever syringe. Pump back and forth until you don't see anymore bubbles. Leave some fluid in lever syringe. Remove caliper syringe and close caliper. Pump lever syringe in and out to get trapped bubbles out of lever bladder. Pump lever full of fluid, remove syringe and close. Flick lever a few times to pressurise system. Voila!

Sent from my M2012K11AG using Tapatalk
 

ozzybmx

taking a shit with my boobs out
Am I a total numpty here?
We all started somewhere.

YouTube, correct tools and a plan. I always use the little bucket for Shimano but 2 syringe would be as good if not better. A lever bleed is essential.

Shimano are the easy ones too, fckn SRAM :mad:
 

The Duckmeister

Has a juicy midrange
Gravity bleed makes the process much harder than it needs to be. Air is fundamentally more buoyant than any liquid, so at all stages of the process you want to be encouraging it to move upward.

A "dry" bleed does need a bit of manipulating 'cos you need to get the caliper properly filled; best done with the caliper demounted so you can move it around to float the air up.
 

k3n!f

leaking out the other end
Gravity bleed makes the process much harder than it needs to be. Air is fundamentally more buoyant than any liquid, so at all stages of the process you want to be encouraging it to move upward.
You have very eloquently described my thoughts. I think the gravity bleed probably works well when you are replacing old fluid, but for a fresh set of brakes full of air it doesn't make much sense.

I ended up pushing 20mL of fluid with a syringe through the system from the bottom up and immediately had a great lever feel. Fixed in under 10 minutes.

Will you revoke my numpty status?
 

Labcanary

One potato, two potato, click
You have very eloquently described my thoughts. I think the gravity bleed probably works well when you are replacing old fluid, but for a fresh set of brakes full of air it doesn't make much sense.

I ended up pushing 20mL of fluid with a syringe through the system from the bottom up and immediately had a great lever feel. Fixed in under 10 minutes.

Will you revoke my numpty status?
No harm no foul. It's all a learning experience. Good on you for getting it working nicely.
 

pink poodle

気が狂っている男
I didn't realise matching things up was a bad thing? Maybe tomorrow I'll post a pic in my rook pyr of the shoes, gloves, sunnies, helmet...
 
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