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Mountain Bike Blog



Mountain Bike Avid Brake Bleed - Success!


This morning I completed what I would call my first major bike maintenance procedure.  Iíve changed tubes, tyres, chains, cassettes, brake pads and rotors, Iíve even strung a few shifter cables but bleeding hydraulic brakes was a step-up.

Prior to starting @backontrack00 gave me some great tips on buying a bleed kit.  The Avid kit contains a couple of very handy things.  A range of caliper blocks and brake pad spacers to ensure your calipers (with or without pads) stay spaced correctly during the procedure and hose camps on the filler tubes.

When purchasing a bleed kit check what is included in the package carefully!  Some online retailers show incorrect images of the kits, specifically an image showing DOT fluid when the kit doesnít contain it.  Make sure you check the description when buying and know exactly what it is you are buying.

The other great tip I received was to watch YouTube videos about brake bleeding.  I didnít have to look too far as Avid have a couple of great videos (http://www.youtube.com/watch?v=IoaPUw5DliA and  http://www.youtube.com/watch?v=GzZkEIrCBJ0) and by studying both of them I got a pretty good understanding of what we were going to do and why.  For me the why is important because it helps me to understand how anal I need to be about getting it 100% right.

Interestingly however neither of these videos linger on a very important point - you donít want to get the DOT fluid anywhere near the brake pads or brake rotor or you are very likely to destroy a set of pads.  If you have a bleed kit with a caliper block there is no reason to leave your wheel on.  So do yourself a favour by removing the wheel, removing your pads and use a caliper block when doing the bleed.

Other tips:

  • Try using the hose clips before filling the syringes with DOT fluid.  Learn how to open and close them with one hand before they get covered in oil.
  • Be patient when trying to get the air out of the DOT fluid.  The more air you get out of the DOT fluid the less air will end up in your brake line.
  • Getting the air out of the syringe can be messy because you will lose some DOT fluid in the process.  After releasing the hose clamp work the air bubbles up the filler tube.  You may need to flick the tube to get the bubbles all the way up. The more air you can work up the tube, and the more fluid you can get to run back down into the syringe the less waste and the less mess you will make when forcing the air out with the plunger.
  • In case itís not obvious you need to do everything in your power to get the air out of the brake system.  This is the main objective of bleeding the brakes, so be patient.  Get all the air out of the calipers, out of the lever and importantly out of the syringe and filler hose before attaching them.  There is no point in pumping air back into the system!  I was very surprised how much air came out of the calipers it took some time to completely clear all the air.
  • In the videos they made the whole process look very clean, I found it far more messy, so my tip is to have your rags and alcohol wipes ready.

Alcohol Wipes:  I picked up a box of 60 individually packaged alcohol wipes for less than $10 from Office Works of all places (but you will find them in chemists etc).  They are great for cuts and grazes, cleaning break disc rotors and wiping off grease and oil from your bike (donít use wetones or baby wipes because they contain other impurities).  I have a few of these stashed in my backpack, my car and toolboxes etc.  Very handy.

If you have any tips on brake bleeding let me know or add your comment.



This website is brought to you by MTB weekend warrior Aaron Markie.
There are plenty of great websites out there with a wealth of information about Mountain Bike Trails,
however in my experience its hard to get a good mix of info, maps, photos and videos of trails I've never ridden.
The idea of this website is to tie those 4 elements together and give you a more detailed look at the MTB Trails I ride.
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