Breadfan

I bought a Niner RTL frame the other day and I was transferring over all my parts form my previous Gravel bike. I have a Tiagra 2x10 groupset that came with those quick connect hydraulic brake hoses. I needed to route my cables and hoses through the dropbars and then through the downtube so I bought new hydraulic hoses. The front went well, bleeding brakes for (my) first time was easy. When I got to the back caliper, I bleed them as I should have but they were very spongy, and would not stop me at all. Tried again, and again, and again, about 12 or 13 times before I finally realized that it was not gonna work. I even put the bike straight up and let the caliper hang, no luck. So, on a whim, I decided to fill the cup on the reservoir (atop the shifter) and then pull it through the caliper in reverse order with the syringe. Low and behold as soon as I started, huge bubbles came through that were lodged in the caliper. Brakes are good and a new way (for me) to do it worked well. Cheers.

choddo

Did you do the old hanging the bike at different angles to get bubbles out of the shifter before that?

p.s. “Lo and behold”

FBinNY 

People often forget an important step for effective bleeding.

We all know that bubbles rise, so orientation of the parts accordingly matters. But people forget that bubbles can cling to walls.

Pour yourself a coke or champagne, and you'll see the bubbles rising, except for those clinging to the glass. Those won't move until you tap the glass to loosen them.

Nurses tap IV lines to clear bubbles and you need to do likewise to encourage air to work its way to the bleed port.

As the OP found air can also get trapped in the caliper, so orient it so the line is on top and tap intermittently for a minute or two.

BTW - brake fluid is fairly viscous, so you need to be patient and give bubbles enough time to work their way to the door.

SoSmellyAir

I have not yet had to bleed my brakes, but what you did sounds like the procedure to bleed brakes on a car. When the "huge bubbles came through", did you see those huge bubbles in the syringe or in the cup?

choddo

Yeah, I was assuming syringe as he was pulling from that end and thought they were trapped in the caliper.

Breadfan

The bubbles went into the syringe since I was pulling it.

t2p

also had a heckuva time bleeding Tiagra brakes on one of my bikes

finally coaxed remaining bubbles in similar way

related note - at one point questioned and almost regretted going with the Tiagra 10 spd shifters / brakes (they were takeoffs) - but after months of use they operate very well … one of my best shifting bikes - and the brakes are also great and now close to power of my XT equipped bikes … only minor issue is the front shifting from 31 to 48t big ring is a tad slow / clunky (paired with GRX front derailleur)

SoSmellyAir

Not having bled bike brakes before, so not sure what the "regular" way entails, but what you did sounds like the way to go to eliminate any air trapped in the brake caliper, rather than hope to dislodge the air pocket and cause it rise up all the way through the brake hose and the STI lever.

Breadfan

Mine also shifts very smoothly. They were also very easy to set up and adjust when I installed them.

Breadfan

All the instructions and videos I’ve watched push the oil from the syringe at the bottom caliper into the cup at the top. Bubbles are supposed to rise but like you said, trapped bubbles are hard to dislodge. I haven’t seen or heard of anyone pulling it in reverse but it paid off.

deacon mark

There is more than one way to bleed brakes. You can do a complete gravity bleed overnight and just let everything run downhill. Then a bit of on/off with the bleed valve in the caliper, and generally you are good to go. However, I have noticed a bit of tweaking is needed at times. To get my own r7000 to actually grab before the brake got too close to the drop bar, I had to do a trick. This is not recommended but works. If you find your brakes are not spongy but they go almost to the bar before you stop then the free stroke needs adjusting. You cannot do this on the 105. I saw a tip on youtube that worked great. I actually left the bleed port screw in the shifter and then push a little bit of fluid up into the brake line. You have to be careful and go only a little but and very slow. Otherwise you can break the bladder that is up in the shifter. Doing this will give you crisper action however you have to watch disk rub and too much and you will lock the brake. If that happens just let a little out the bleed value again.

Polaris OBark

A syringe is a tried and true method for de-gassing a fluid. I sometimes put one at each end.