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ECUdude
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Rear Brakes squishy
08/21/14 at 12:28pm
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Noticed yesterday on the trail that my rear brakes are almost gone.  The lever has almost no resistance and i can pedal through while applying the brakes.  Almost endo'd the bike the first time.  Bike is a Trek Mamba(09ish?)  Discs front and rear.  I know almost nothing about maintaining bikes, but have extensive knowledge of car/motorcycle etc.  Are these hydraulic disc brakes or mechanical linkage?  Im going to tear into it tonight.  Anything I need to look for?

Zack
  
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Slothzilla
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Re: Rear Brakes squishy
Reply #1 - 08/21/14 at 1:00pm
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Your brakes are likely hydraulic but without knowing the model or seeing a picture, it is only an educated guess.  Let us know what make/model brakes you have and it will be much easier to provide pointers on what to look for.
  
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bikermedic
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Re: Rear Brakes squishy
Reply #2 - 08/21/14 at 1:33pm
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Start simple first,  Look at the pads.  That should be the same for hydraulic as well as mechanical.   Make sure the pads are not contaminated with chain lube etc.  If so, change the pads.    Last but not least assuming they are hydraulic, they may need to be bled.  If I were you I would take it to a shop or have someone who has bled bike brakes before show you how to do it the first time.  You most likely will need a bleed kit for the particular type of brakes you have.  If by chance they are mechanical disks, use the barrel adjustor on the brake lver to tighten up the cable.   

G
  
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ECUdude
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Re: Rear Brakes squishy
Reply #3 - 08/21/14 at 2:00pm
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I looked the bike up on Treks bike archive.  It looks like its a 2010.  Specs for the brakes are:
SRAM BB5 mechanical disc brakes, 6-bolt; 160mm rotors.

Now before riding yesterday, I did clean up the bike and lube everything. The pads might have become soaked etc.  However that doesnt explain the soft feeling in the lever.  I'm assuming there is some kind of adjustment mechanism that I can play with for harder brakers or softer correct?  I'm going to tear into it today after work and will hopefully be able to post some pics and get it working correctly.  Also, I'm assuming that any LBS will have the pads?  I know what ASSume means  Smiley.  Thanks for the quick replies.

Zack
  
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Re: Rear Brakes squishy
Reply #4 - 08/21/14 at 3:23pm
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There is an inside pad adjustment on the BB5's.  If the pads aren't gone, adjust the inside pad with the thumbwheel on the same side as the pad until it just clears the rotor.  You can adjust the outer pad only by adjusting the cable at the brake caliper.  If you have adjusted the brake using the quick adjusters at the levers, make sure they are screwed all the way in before adjusting the cable at the caliper.  BB7's are much easier.
  
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ECUdude
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Re: Rear Brakes squishy
Reply #5 - 08/21/14 at 9:42pm
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so apparently they are not BB5s. The lettering on the inside says they are BR-M446 Malaysia.  They appear to me to be hydraulic brakes as i can see the bleed valve on the backs of them. I'm going to ASSume(again Roll Eyes ) that you can bleed these like normal discs on cars/motorcycles etc.  If this is the case, I have all the tools to do it with.  Also, recommended fluid to refill with?

This is what I have.

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Tom F
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Re: Rear Brakes squishy
Reply #6 - 08/22/14 at 12:16am
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Use mineral oil to refill the reservoir, and check you tube for procedure.
  
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Re: Rear Brakes squishy
Reply #7 - 08/22/14 at 10:53am
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I still think it's your pads are contaminated.   Giving the wash and lube right before it started.
  
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ECUdude
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Re: Rear Brakes squishy
Reply #8 - 08/22/14 at 2:44pm
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i noticed the lever was starting to creep more before the wash/lube.  The pads look fine and look just like the front ones.  Going to get a shimano brake bleed kit and try bleeding them.

Zack
  
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sager
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Re: Rear Brakes squishy
Reply #9 - 08/22/14 at 3:11pm
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at any time did you flip the bike upside down before it got bad?  Some brake systems have problems with air getting into the system.
« Last Edit: 08/22/14 at 3:11pm by sager »  
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ECUdude
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Re: Rear Brakes squishy
Reply #10 - 08/23/14 at 7:09pm
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Yeah I had the bike upside down for a while. But I started noticing it before that. Getting ready to bleed them so we will see. 

Zack
  
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Re: Rear Brakes squishy
Reply #11 - 08/24/14 at 2:02am
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Definitely agree with the YouTube suggestion. That's how I figured out how to bleed/fill my Hayes Nines which are notoriously painful to get bled right. Found a great step by step. I'm sure there's something like that for the shimano's. 

Hope you get it sorted out.   

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Re: Rear Brakes squishy
Reply #12 - 08/28/14 at 4:29pm
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So finally got the shimano kit in to bleed the brakes, got them bled and the lever is back to "normal" working condition.  went and rode at N. Meck with the wife and still having problems with the rear brake.  So it looks like it might have been a combination of failing brake pads and air in the lines.  I've noticed that I favor the rear a lot more than the front.  Is there an upgrade to the pads that I can get? Or will the stock pads do the trick?

Thanks for the help guys

Zack
  
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Re: Rear Brakes squishy
Reply #13 - 08/28/14 at 7:54pm
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KomodoDragin wrote on 08/24/14 at 2:02am:
Definitely agree with the YouTube suggestion. That's how I figured out how to bleed/fill my Hayes Nines which are notoriously painful to get bled right. Found a great step by step. I'm sure there's something like that for the shimano's. 

Hope you get it sorted out.   

GO PIRATES!

I have found the Hayes HFX/Mag 9's to bleed better than Avid, Formula and some others.  The Shimano's are pretty straight forward and yield good, quick results.  Hopes you just bleed like a motorcycle or care and you're done.
  
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