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  1. #1
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    How To Check For Proper Bleed Job?

    Now pardon me if it seems totally obvious, but I am a newbie! I installed LX hydraulic brakes on my bike a little while ago. My bike used to have a non-series Shimano mechanical disc brakes.

    The installation went smoothly, without any problems whatsoever. Well, the only problem was trying to find the caliper fixing bolts which I had lost after I ripped the packaging in excitement, and the contents exploded out!

    So the brakes are installed and everything went as per the instructions. The brakes are doing their job well... stopping the tires when needed to....

    The question- how do I know for sure if I have bled the brakes properly. Just because the brakes are stopping the tires enough to declare a proper bleed? I turned the bike upside down, depressed the lever several times, and still they are working the way they should.

    The levers feel good too... not totally firm... and not completely soft that it touches the handlebars...

    Since it is the first time I worked on hydraulic brakes, I am very skeptical of the fact that I got everything right the first time...

    What would be an ultimate test to see if the brakes are bled properly or not?

    Thanks a lot!

  2. #2
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    Quote Originally Posted by anirban
    Now pardon me if it seems totally obvious, but I am a newbie! I installed LX hydraulic brakes on my bike a little while ago. My bike used to have a non-series Shimano mechanical disc brakes.

    The installation went smoothly, without any problems whatsoever. Well, the only problem was trying to find the caliper fixing bolts which I had lost after I ripped the packaging in excitement, and the contents exploded out!

    So the brakes are installed and everything went as per the instructions. The brakes are doing their job well... stopping the tires when needed to....

    The question- how do I know for sure if I have bled the brakes properly. Just because the brakes are stopping the tires enough to declare a proper bleed? I turned the bike upside down, depressed the lever several times, and still they are working the way they should.

    The levers feel good too... not totally firm... and not completely soft that it touches the handlebars...

    Since it is the first time I worked on hydraulic brakes, I am very skeptical of the fact that I got everything right the first time...

    What would be an ultimate test to see if the brakes are bled properly or not?

    Thanks a lot!
    Since the lever feel seems good now (can't pull to the bars?), the test is to see how they do on a ride with a nice long downhill. If they feel fine during and after the downhill, nothing more is required.

  3. #3
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    Properly bled brakes should feel nice and firm. Squishy lever usually means air in the system.

    If you turn the bike upside down for a while, then turn it rightside up. And then pump the levers, if it gets real squishy or pulls to the bar, then you've got air in the system.

  4. #4
    Nightriding rules SuperModerator
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    Yep.. exactly...from my experience with prebuilt Shimanos..usually they are almost perfect.... they usually improve a little bit in firmness at the lever after I bleed them (usually when I cut the lines)

  5. #5
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    When you turn the bike upside down the air at the top of the reservoir is suddenly right up by the piston. When you move the lever you pump air into the line. Do that enough and even flipping it over and pumping it will not get it all out.

    The second you touch the lever the pistons and pads should move. When they're solidly on the rotor and it's not turning you should be able to pull the lever to the bar as hard as you can without feeling it "bottom out" inside the master cylinder.

  6. #6
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    Quote Originally Posted by fsrxc
    the test is to see how they do on a ride with a nice long downhill. If they feel fine during and after the downhill, nothing more is required.
    That might be a very painful way to find out if the brakes are bled properly or not... you know what I mean!? What if you are bombing along your favorite downhill trail, and then you realize that the levers are drilling thru the handlebars..... and the computer reads 50miles/hr...

    But what you said does make sense.. thats the ultimate, fool proof way to get it tested. But I was thinking of something more along the lines when the bike is still in the workstand...

    Thanks a lot for the replies!

  7. #7
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    I have had the bike flipped over and pumped the levers- the brakes were able to stop the fast spinning wheel (without any load though). and the pistons retracted as I neutralized the lever.

    I returned the bike to its upright position, and it felt the same as before- as soon as I apply little effort to the lever, I can see that the pistons reacting to it.. and within 1/3 of the levers' travel, the pistons are fully engaged, and the levers refuse to come any closer to the handlebar.

    I have had the levers engaged and then tried to pedal- and the brakes did a great job of having a death grip. I havent had a chance to load-test the brakes enough yet... maybe 10minutes of street riding- and the brakes behaved better than the mechanical ones I had. Living in Buffalo NY, its hard to go out with so much snow being dumped these days.

    What is the definition of a lever being "spongy/squishy"? does that mean that the lever comes all the way to the handlebar- without any (or marginal) feedback from the caliper end? Or just that there is minor, uneven resistance while pressing the lever?

    I have read tons of stuff in this forum about brake problems because of failure to bleed them properly (most of the riders being very experienced)... thats why I am questioning my ability. I am a total noob, and I just cant accept that I was able to bleed the brakes fine the first time..... so I was to make sure- dont want to use my shoe as a brake while on a trail...

    Thanks!
    Last edited by anirban; 02-02-2007 at 05:03 PM.

  8. #8
    Nightriding rules SuperModerator
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    Quote Originally Posted by anirban

    What is the definition of a lever being "spongy/squishy"? does that mean that the lever comes all the way to the handlebar- without any (or marginal) feedback from the caliper end? Or just that there is minor, uneven resistance while pressing the lever?

    It sounds like your brakes are fine....

    the "sponginess" is just that when you engage the brakes once the pads contact the rotor fully, the lever doesn't feel solid, but you can push it a bit still although the pads cannot press more against the pad...

  9. #9
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    Best test....crank along on the flat and really pull only the front brake, if you start to nose wheelie you know you're good I'm almost serious about this.

    My HOPE Mono Mini's I thought were excellent straight out the box and they worked fine, stopped me when I needed to stop ( I did cut the hoses to shorten them but never bled them after) but never really had that "bite" to them, but where definitely better than any other disc brakes that others had when I tried them.

    Well the other day I decided to bleed the front because it didn't seem to be stopping quite as good as it used to and holly crap when I was done the feel was nice and "crisp" when I engaged them and it could send me OTB super easy. Then the rear wasn't feeling so good, so I gave that a real good bleed and whoa now I can stop on a dime and give you back a nickel change

    They were about a year old and had on about 3,700 miles so they were prob due for a fluid change anyhow and that's why they started to feel less and less powerful.
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  10. #10
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    Quote Originally Posted by LyNx
    Best test....crank along on the flat and really pull only the front brake, if you start to nose wheelie you know you're good I'm almost serious about this.
    Hmmm... this is something I might actually try! Thanks!

    How did you check your rear wheel? Press it to lock up while riding on the flat?

  11. #11
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    Quote Originally Posted by Danke
    When you turn the bike upside down the air at the top of the reservoir is suddenly right up by the piston. When you move the lever you pump air into the line. Do that enough and even flipping it over and pumping it will not get it all out.

    The second you touch the lever the pistons and pads should move. When they're solidly on the rotor and it's not turning you should be able to pull the lever to the bar as hard as you can without feeling it "bottom out" inside the master cylinder.
    Flipping it is not to get the air out. If it is bled properly, there should be no air in the system anyways. I've left my bike upside down for days at a time.

    A spongy or improperly bled brake can still stop you when it's cool... but after that system heats up, you're in trouble.

    As for the definition of spongey lever? Imagine a mechanical disc brake with gunked up lines. Or imagine a v-brake with the pads set up with tons of toe.

  12. #12
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    yup

    Pretty much, yup. With a good set of discs you shouldn't need to apply too much pressure to lock up any wheel, especially on asphalt.
    Quote Originally Posted by anirban
    Hmmm... this is something I might actually try! Thanks!

    How did you check your rear wheel? Press it to lock up while riding on the flat?
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  13. #13
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    Quote Originally Posted by XSL_WiLL
    A spongy or improperly bled brake can still stop you when it's cool... but after that system heats up, you're in trouble.
    Well, I guess I have to hit a 20mile downhill and heat the brakes to find out if they are bled or not.... most probably painfully- because the bike is a hardtail.

  14. #14
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    My shimano XTR instruction defined firm as about 3/8 inch to 1/2 of lever movement from first engagement to full hand pressure.

  15. #15
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    Just remember that if these are new brakes they need to be "beded in" so don't expect them to perform super straight out the box and if you go trying something like this you might have a bad experience.

    Quote Originally Posted by anirban
    Well, I guess I have to hit a 20mile downhill and heat the brakes to find out if they are bled or not.... most probably painfully- because the bike is a hardtail.
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  16. #16
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    Quote Originally Posted by jeffscott
    My shimano XTR instruction defined firm as about 3/8 inch to 1/2 of lever movement from first engagement to full hand pressure.
    Pad wear and amount of fluid in the system will also dictate the amount of lever travel.

  17. #17
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    Quote Originally Posted by anirban
    That might be a very painful way to find out if the brakes are bled properly or not... you know what I mean!? What if you are bombing along your favorite downhill trail, and then you realize that the levers are drilling thru the handlebars..... and the computer reads 50miles/hr...

    But what you said does make sense.. thats the ultimate, fool proof way to get it tested. But I was thinking of something more along the lines when the bike is still in the workstand...

    Thanks a lot for the replies!
    Ok, I didn't say the obvious:
    Quick road test or test on the trail on a small downhill, before hitting something big that could kill you if the brakes failed.

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