Brake bleeding done right??

Discuss light weight issues concerning road bikes & parts.
Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Hi guys, I know this has been covered lots of times, but I would like some advice. When I build up my 9170 bike, I bled the front and rear brakes. The rear has been fine from day 1 (and now 7000 km later), the front one, on the other end, has never been as great. I've bled it again and eliminated some bubles, but even after that, it was not right. After a new bleed (no bubbles to see), the lever stroke was OK again (but feeling still not as firm as the rear) The thing is, after a few rides, especially with cobbles, the lever stroke gets worse again on the front (rear still perfect). So, I would like to know the difference between the different methods (wheel + pads removed, yellow bleed block in place):

-basis bleed with only the reservoir on top of the lever with some fluid in it + some lever pulls (done multiple times)
-full bleeding with rubber hose attached to the caliper and brake pull + bleed port opening ( done multiple times also)
-full bleeding from bottom to top with a seringe (never done)
-zipp tie on brake lever overnight (done 2 times, good feel on the lever at first, but gets worse again over time)

As anyone had the same problem of lever stroke going from OK to way to long after a rough ride? It's as the air in the system gets free with all the vibrations, but as it's a closes system, I can't imagine air coming IN the system with vibrations (and there are no visible bubbles when I bleed) Would you advise the seringe method? From the numerous videas I saw on youtube, that method seems to always introduce some air in the system as it's almost impossible to get the seringe + rubber hoose completely air-free. Any other advice is welcome. I can take the bike to the bike shop, but that is really the last step for me (I don't really trust them, I've heard too many stories of crappy maintenance jobs around me )

simoncx
Posts: 99
Joined: Sun Nov 15, 2009 12:27 am

by simoncx

If the lever goes soft on rough roads then there is air in the system somewhere, I've had it happen on my new cross bikes last year on the first bumpy ride. A quick way to check is put on the bleed block and shimanos bleed cup on the lever filled with oil and press and release the lever letting it snap back and every couple times pull the lever in hard and keep it there for a few seconds, usually you will start to see air come out. Also try tapping the the caliper and hose while doing this so it will release the air bubbles sometimes tilting the bike alittle down or up helps. I think I had to do mine 2-3 times before they were right, I did the syringe method and still had the same thing happen in a bumpy race.

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Lewn777
Posts: 257
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

How old are your brakes? From new they should feel excellent for at least the first year. Shimano brakes should be very easy to bleed and they are very resilient to air being in the system as the bubbles should rise to the reservoir over time.

I'd suggest that your front brake might be leaking around the caliper. Try what Simoncx is recommending first, and if still no joy you might want to take them to a bike shop to get them looked at or possibly warranteed.

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wheelbuilder
Posts: 431
Joined: Wed Feb 08, 2017 2:10 am

by wheelbuilder

If you are not using the syringe method, you should be doing so. Do you have a Shimano funnel? your post isn't clear about that. Push clean new fluid with sysringe through caliper and up to funnel until bubbles stop. Then do it again. You can use variations also. Gravity bleed with fluid filled funnel and open bleed port at caliper. Closed lever reservoir and pushing then pulling fluid through caliper etc. If your bleed is good and you just want to firm up the lever feel or reduce lever stroke.................either remove wheel and insert orangish/red pad spacer, or just leave the wheel in there and protect the rotor with rags..........VERY carefully force some extra fluid into the caliper through the bleed port. Push on syringe until a hard stop is felt, close bleed port and carefully remove syringe without splashing. You can fine tune your lever feel by doing this. Either forcing excess fluid into caliper for firmer brakes, or burping one drop at a time to soften them up. PM me if you want step by step.

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Thx for the first advices here. To answer the questions : the bike is 6 months old, 7000 km's. I have the Shimano funnel incl adaptor for the weird new DA treads. I did what Simoncx wrote, but will do it again this evening and really take my time. After that, as the funnel is already screwed in, I will push new fluid from the caliper up into the funnel and hope the result will stay as it should. I have faith in Shimano, as the rear brake is really perfect, so it CAN be done :wink:

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Lewn777
Posts: 257
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Delorre wrote:
Mon May 14, 2018 7:02 am
Thx for the first advices here. To answer the questions : the bike is 6 months old, 7000 km's. I have the Shimano funnel incl adaptor for the weird new DA treads. I did what Simoncx wrote, but will do it again this evening and really take my time. After that, as the funnel is already screwed in, I will push new fluid from the caliper up into the funnel and hope the result will stay as it should. I have faith in Shimano, as the rear brake is really perfect, so it CAN be done :wink:
Ok so 6 months and 7000kms.

Scenario 1 (most likely). During original factory assembly the front brake wasn't properly bled and what you've done thus far hasn't remedied the situation.
Scenario 2 (possible). A hydraulic line is under-torqued or some other seal is letting in air and lightly weeping oil.

Have a look on youtube and follow all the instructions very carefully pausing the video at each stage. https://www.youtube.com/watch?v=nQ5Bnddm72E

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Lewn777 wrote:
Mon May 14, 2018 12:02 pm
Delorre wrote:
Mon May 14, 2018 7:02 am
Thx for the first advices here. To answer the questions : the bike is 6 months old, 7000 km's. I have the Shimano funnel incl adaptor for the weird new DA treads. I did what Simoncx wrote, but will do it again this evening and really take my time. After that, as the funnel is already screwed in, I will push new fluid from the caliper up into the funnel and hope the result will stay as it should. I have faith in Shimano, as the rear brake is really perfect, so it CAN be done :wink:
Ok so 6 months and 7000kms.

Scenario 1 (most likely). During original factory assembly the front brake wasn't properly bled and what you've done thus far hasn't remedied the situation.
Scenario 2 (possible). A hydraulic line is under-torqued or some other seal is letting in air and lightly weeping oil.

Have a look on youtube and follow all the instructions very carefully pausing the video at each stage. https://www.youtube.com/watch?v=nQ5Bnddm72E
After collecting, i've re-done and shortened the front and rear brake hoses. In the proces, I lost a fair amount of oil , front as well as back. I refilled and bled both brakes. it's very likely I introduced a fair amount of air in the housings, but I got rid of it for the rear and not for the front :cry: I will have a look at scenario 2 also, as I have the impression that the bolt that fixes the hose into the caliper at front a less screwed into the caliper as in the rear. As far as I can see, I don't have any leaks. It's been really dusty the previous weeks and there is no extra dust attracted to the front caliper or whatsoever.

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Lewn777
Posts: 257
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Delorre wrote:
Mon May 14, 2018 12:55 pm
Lewn777 wrote:
Mon May 14, 2018 12:02 pm
Delorre wrote:
Mon May 14, 2018 7:02 am
Thx for the first advices here. To answer the questions : the bike is 6 months old, 7000 km's. I have the Shimano funnel incl adaptor for the weird new DA treads. I did what Simoncx wrote, but will do it again this evening and really take my time. After that, as the funnel is already screwed in, I will push new fluid from the caliper up into the funnel and hope the result will stay as it should. I have faith in Shimano, as the rear brake is really perfect, so it CAN be done :wink:
Ok so 6 months and 7000kms.

Scenario 1 (most likely). During original factory assembly the front brake wasn't properly bled and what you've done thus far hasn't remedied the situation.
Scenario 2 (possible). A hydraulic line is under-torqued or some other seal is letting in air and lightly weeping oil.

Have a look on youtube and follow all the instructions very carefully pausing the video at each stage. https://www.youtube.com/watch?v=nQ5Bnddm72E
After collecting, i've re-done and shortened the front and rear brake hoses. In the proces, I lost a fair amount of oil , front as well as back. I refilled and bled both brakes. it's very likely I introduced a fair amount of air in the housings, but I got rid of it for the rear and not for the front :cry: I will have a look at scenario 2 also, as I have the impression that the bolt that fixes the hose into the caliper at front a less screwed into the caliper as in the rear. As far as I can see, I don't have any leaks. It's been really dusty the previous weeks and there is no extra dust attracted to the front caliper or whatsoever.
If there's no oily extra dust anywhere including inside the caliper, then yes it must be air trapped in the system. it's just that I've always found Shimano to be so user friendly vs say SRAM (which is very finicky due to gassy brake fluid in a smaller system than it was really designed for), I find it difficult to understand how you could screw it up, especially a front brake. :noidea: There is history of Shimano systems leaking behind the pads if a seal around the piston is compromised, very rare though.

scale29
Posts: 43
Joined: Sat Jun 04, 2011 5:40 pm

by scale29

It’s not that rare actually, quite well documented. I myself had a ceramic piston disintegrate at the back which damaged the Caliper.

Anyhow, I always use a caliper to lever bleed on Shimano using the syringe and not had a bad bleed yet. Do check the fittings are tight too, as sometimes a small leak isn’t noticeable.

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

After leaving a zipp tie on the lever overnight, I took my time yesterday evening to do it correctly. The key was really tapping the hoose + caliper + lever, pull the lever, tap again etc. I was amazed of the pulls and taps it took no to have any bubbles coming up anymore. Tilting the bike also helped to release some air. After that, I did a bleed from top to bottom, but no air anymore. If really the leaver goes bad again (I hope not, the feal is really great at the moment), I can try the seringe method. We will see after a few rides how it goes. Thx for the replys guys! Just for my personal info : what's the difference between a bleed lever to caliper (without seringe) vs caliper to lever (with seringe). Both make fluid travel through the system, but is one method more effective than the other?

scale29
Posts: 43
Joined: Sat Jun 04, 2011 5:40 pm

by scale29

My reasoning is.... When you push the oil from caliper to the lever, any air usually ends up at the lever and makes it into the resevoir, doing it the other way could push air and trap it behind the pistons. Although in reality I doubt it matters much, it's probably a bit quicker with the syringe.

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

Some update on this : even after the last full bleed done just before my last post here above, the lever went soft again after a few rough rides and lever stroke was back to 'too long'. In additoin to that, left piston (seen from riding position) didn't go back very well. The other one was fine. I cleaned both pistons (letting them come out a fair bit to allow a good clean), although they were just a little dusty. I changed the brake pads at the same time, they were worn anyway. Unfortunately, all this didn't help, and in the end, after 5 or 10 rides, the left piston was in constant contact with the disc. I guess that with every brake pull, the left piston only retracted for let's say 99,9%, causing that piston to go out of allignement after lots of braking.

As I was completely desperate, I bought a new front caliper. Did the install today, it took some time and lots of oil to get the front caliper filled up and air free. Thing is, I came to a point really no air bubbles were coming out from the funnel reservoir or hose at the bottom (did it with the bleed block in place of course!!), but lever feel is still not as firm as the rear brake. Went on with pad install + brake allignement. The final result is not bad, but:

* brake feel is not 100%, still feels a little soft.
*compared to the back, both front pistons retract a lot less. They move both ways in synchro (not so with the old caliper), but don't go back near as good as on the rear ones. Is this due to air remaining in the system? I didn't try the seringe method as I don't have enough fluid left and no mather how well I tried, really no air is coming out anymore.

I don't know what to do next apart from taking the bike to a lbs, to pay 40€ for a bleed job and hoping for the best. Just have to find a good one, don't want to throw 40€ out of the window fo nothing.

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ms6073
Posts: 2406
Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

Really a shot in the dark, but since you mentioned this was a R9170 setup, are you using Shimano BH-90 hydraulic hose because your description on lever feel suggest to me that you are using BH-59 hydraulic hose introduced for the ST-R785 shifters.
Michael - The Anaerobic Threshold is neither...

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

ms6073 wrote:
Mon Jun 18, 2018 2:54 pm
Really a shot in the dark, but since you mentioned this was a R9170 setup, are you using Shimano BH-90 hydraulic hose because your description on lever feel suggest to me that you are using BH-59 hydraulic hose introduced for the ST-R785 shifters.
Hoses are the ones that came with the full build bike, I only shortened them and re routed the hoses. So, pretty sure it's BH-90 😉 The rear is perfect, front should be the same as all the components are the same.

Delorre
Posts: 933
Joined: Sat May 24, 2014 12:09 pm

by Delorre

I came across this document : http://www.starmtb.com/pdf/ResettingPistons.pdf Is this somethibng you should do after bleeding? I didn't see this in any of the bleeding videos I saw on the net. Is this common practise?

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