UKH

Why is it so bleeding difficult? I've never managed on any disc breaks. Failed on avids and now just failed on 105s. I've followed the instructions and still it's full of air! Bleeding spongy! Grrrr!

In reply to NorthernGoat:

Shimano 105 are easy. Funnel at the lever, syringe at the caliper, push fluid (and air) up through the system and out into the funnel

In reply to r0b:

Yep did that! I'll try again tomorrow....

In reply to NorthernGoat:

It got a lot easier after I realised I can take the calliper off and have gravity work however I want it to.

In reply to Longsufferingropeholder:

Yes, did that as well! Oh FFS, I'm feeling pretty insecure about myself right now! 

In reply to NorthernGoat:

It's "BRAKES", fhs!

Back on topic, I've bled a few types (Shimano, Avid, Hayes, I think), without too many issues.

r0b is on the right lines with filling up from the caliper, because the air rises.

It helps to position the bike so that there aren't any low spots in the hose that could trap air.

Also, squeezing the lever fast and releasing it slowly and lots of tapping the hose can help clear air.

Make sure it's not sucking in air anywhere at the caliper.

NEVER shake the bottle of brake fluid. It's interesting to half fill a syringe with fluid, point it upwards put your finger over the end and try to pull the plunger out further - any micro bubbles of air should expand and rise to the top, where they can be easily released.

In reply to NorthernGoat:

i find these a patience thing, they say do this/that (pulling lever/tapping the caliper) 5 times or what ever but it some times takes ages I havee found and eventually gets there.

In reply to LastBoyScout:

That's a good point about it being brakes not breaks. Now I'm worried about my spelling as well. 

With the lever squeeze, are you doing that when the bleed port is still open?

In reply to NorthernGoat:

Yup generally pretty easy, the only ones I've ever had issue with is Magura.

Just takes a bit of practice.

After you've bled the brake close the caliper valve but keep the lever screw off. Squeeze the lever firmly a few times and hold it then release, wait for any bubbles to rise and top it up, repeat till no more bubbles come up.

Brakes brakes brakes 

In reply to NorthernGoat:

On my shimano gravel levers, I seem to remember the internal hydraulics of the level meant that you should tip the whole lever back about 45 deg in order to release air in the lever itself. Otherwise, patience, hose flicking etc. and it worked fine. I believe I used a helpful Park Tools youtube video too, but I don't have the time to look for it right now.

In reply to LastBoyScout:

One tip I learned recently is to do this repeatedly (if you have a SRAM kit with the pinch clip - or any way of properly sealing the end of the syringe - it's much easier) over the course of a few minutes. You'd be surprised how much air appears out of nowhere within the fluid. Not sure of the physical explanation for this, or how much difference it makes to the final bleed. But I've started doing on it all the time now, on the principal that any air = bad.

OP: Bleeding brakes is definitely a knack where, over time, you will learn a few tricks (like those mentioned already in this thread) that will eventually make it fairly quick and easy. Also, each different type/manufacturer of brakes has it's quirks: I remember the first time I bled SRAM brakes, after years of successfully bleeding Shimano and Hope brakes, and the result was completely rubbish. But with more practice I got there in the end. Keep at it!   
 

In reply to NorthernGoat:

It's often difficult to get all the old oil and bubbles out of the caliper because of the shape and the position of the bleed nipple/attachment. A useful tip is to take the caliper off, remove the pads, clean around the pistons and then, after attaching the bleeding kit to the caliper, open the bleed screw and fully push in the pistons to get all the old gunk out before you go putting fresh fluid in. 

Otherwise you are pushing gunk around, diluting it with new fluid, and it takes much longer. 

Tapping the caliper and hose while bleeding as mentioned above is also a good way to dislodge bubbles.

Hope that helps.

In reply to gethin_allen:

So rebled the brakes tonight. Lever bites in the correct position but it doesn't get lock out tight. On my GRX equipped bike the rear wheel will lock out. With these re-bled 105s the pads engage but as you'd expect but without enough grip to lock the wheel. 

Any further suggestions?

In reply to NorthernGoat:

 I have vastly more experience bleeding mtb brakes than road (shimano make it a doddle), I'm still on calipers as I only really ride road in summer so I've never felt the need to upgrade (Oooooh controversial.. ;p)

But-

Is there any chance there's a leak? Particularly around the brass olive- the only time I've had this (dogsht Magura levers aside but that's a different story) replacing the fittings where the line goes into the lever sorted the problem. 

Shimano kit is usually pretty easy to work with. You've probably already seen them but GCN's Youtube channel often have great "How to" videos that tend to make a lot more sense than the manufacturers instructions.

In reply to NorthernGoat:

I've only ever done it once so maybe I was lucky but I got it right on the first try.

I followed the Bleedkit.com instructions, as that is the exact bleed kit I used. Shimano 105 levers FWIW. Pushing fluid up from the caliper and just slow and steady seemed to do the trick. 

In reply to NorthernGoat:

Are they new pads? If so, they’ll take a short while to bed in, then they’ll work great. If not, do the brakes squeal at all? If so then it’s likely to be contamination.

Brake fluid is very slippy so if you even one drop anywhere near your discs or pads then you’ll have much lower power. Clean the disc thoroughly with isopropyl alcohol. Remove the pads and clean the caliper too. Check there is are no leaks from the caliper. For the pads the best option is to replace them, but obviously that’s costly; I have had some success with burning them (seriously!) over a gas flame, then taking a file to them to remove the top layer - it can be hit and miss though.

In reply to Alun:

I remember when I first tried to do brake maintenance (bleed/rotor clean/pads) I'd spend forever ensuring I was doing it properly then my brakes feeling worse than they were before. Felt like a right idiot when I realised you had to bed brakes in after cleaning.