Results 1 to 7 of 7
  1. #1
    mtbr member
    Reputation:
    Join Date
    May 2013
    Posts
    4

    Elixir 5 clamping the rotor as the day heats up

    I purchased an Elixir 5 Hydraulic brake for the rear of my bike due to a brake giving out days prior to the last 24 Hours of Moab race in October. The brakes are auto adjusting and have worker wonderful until summer is now returning and the temperatures are climbing. In the morning when the temps are in the 50's the brakes work like they always have. While at work the bike sits inside the building and stays around 70 degrees. Now the temps are climbing above and 80 degrees and when I take the bike outside in the summer temps within about a mile the brakes are clamping on the brake rotor and the handles no longer have any travel. I expanded the travel of the brake handle and this lessened the clamping a bit.

    I can't seem to find this problem anywhere on the web and my local bike shops is suggesting they may need to be bled. However, any time I have needed brakes bled it's because they got mushy from air, not super clamping due to air.

    Anyone give me some help here or aware of this problem and a possible solution?

    Oh, and hello everyone. Haven't been on the site in about 10 years. Good to see it still going.

  2. #2
    mtbr member
    Reputation: gmats's Avatar
    Join Date
    Apr 2005
    Posts
    2,199
    I've read your post and am imagining two possible scenarios. Before I go there, I'll try to describe how the brakes (hydraulic) work so that I might be able describe what you might be experiencing. Notice all the"might" in the last sentence.

    OK, so you pull on the brake lever, a piston compresses the fluid in the line which transfers this pressure to the brake caliper. Now with this pressure distributed over a large area, you get a nice big force to push the piston out and engage the pads on to the rotor. All good, simple.

    Now realities. The pistons have to have some level of friction (I used to think you want them to move with very little friction). The caliper (piston) seals are square, not round. So as the pistons move with the pressure, instead of just sliding along the seal, it sort of "bends" the seal a bit. Now when you release the lever, the pressure is reduced and the "bent" seal springs back and allows the pads to retract. All good stuff again. So if the piston(s) or seals get worn out, they loose that spring. One of two things happen. Your pads extend and never retract OR one piston extends more than the other (one pad drags horribly). Either way, not good. By the way, with the square seals, eventually, the pad wears enough and then the piston actually slides a bit in the square seal there by taking up some of the space from the worn pad. This is how they keep auto adjusting.

    OK, 2nd thing now. Remember the lever piston pushing and creating the pressure? Fluid expands with a temperature change. All fluid. Brake fluid, mineral oil, and of course water. Water will expand quite rapidly with a small temperature change. So if the brakes were bled and filled when the temperature was cooler and now there is water in the lines AND even more dramatic, with nice, fat, new pads, then that expansion can easily expand causing that experience you're having.

    It is possible to "overfill" Avid levers such that expansion can cause what you are describing. Possible solutions? In order of "simplest" to most complicated?

    1) Remove wheel, pry pads apart and remove the bleed screw from the lever, see if you get "seapage" of the brake fluid out the lever. This could cure the over filled condition. It won't fix the contaminated fluid condition.

    2) Bleed the brakes. This could get rid of any potential water in the line. It can also change the "overfilled" condition. It won't solve the piston/seal problem, might help but won't fix it.

    3) Rebuild the caliper with new pistons/seals and then fill/bleed the system. This will (should?) fix the condition you are having.

    Hope this helps and helps a bit with the understanding. Sorry for the long winded reply. Good luck with that, post back up when you find the solution.

  3. #3
    mtbr member
    Reputation:
    Join Date
    May 2013
    Posts
    4
    Thank you for the reply. I sure hope these brakes are not worn out since they literally have less than two weeks of use. I did buy them last October, used them for the 24 Hours of Moab, and have since (due to a race injury) only used them the last five days.

    So the fill is from the factory and has never been bled. However, I will try prying them and see if they I get seepage back. I have to do something as the drag is more of a clamp on the rotor. When off the bike going across dirt the tire will lock up and drag.

    Thank you again.

    On a side note... I sure hope this fixes it. My Elixir 3 is 3+ years old and working flawlessly. Elixir 5 less than 3 weeks of use and not so good.

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2013
    Posts
    12
    I have to do something as the drag is more of a clamp on the rotor.

  5. #5
    mtbr member
    Reputation:
    Join Date
    May 2013
    Posts
    4
    Removed the brake, pried the pads open, cracked the bleed valve, and while the pads were still under pressure I closed the bleed valve. All is good right now. Will see what it's like in the morning after the cooling of the night and then the heating of the day. Will report back.

    Thanks again.

  6. #6
    mtbr member
    Reputation: gmats's Avatar
    Join Date
    Apr 2005
    Posts
    2,199
    Oh man, I get the feeling I wasn't clear. You want to bleed the excess fluid from the lever side, not the caliper. Hope you didn't allow fluid to enter the system and a bubble to travel up into the system. Well, we'll see. Hope it all works out.

  7. #7
    mtbr member
    Reputation:
    Join Date
    May 2013
    Posts
    4
    Quote Originally Posted by gmats View Post
    Oh man, I get the feeling I wasn't clear.
    LOL! Actually, I'm well versed on hydraulics, but really appreciated you taking the time to give a thorough explanation which I'm sure will be very helpful just to have archived. With that said, I asked my question because you never know what quirks might be particular to any system.

    Your explanation helped me to chew over my problem and rule out certain things like the worn seals not really being in the realm of likely in the least. The overfilled brakes didn't make a whole lot of sense since they are straight out of the factory. However, it did make the most sense (overfilled) that the heat expansion must be causing the pistons to compress.

    This is what I did. While the pistons were still clamping down I removed the caliper, pushed a screwdriver in between the pads, and cracked the bleed screw at the lever. I drained off, going to be technical here, about two large drips of fluid. Closed the lever bleed valve while the pads were still under pressure and finally cleaned up the brake fluid.

    Results: I gave it a couple days before revisiting this thread so as to not reply too soon... The brakes now work flawlessly and correctly.

    GMATS I want to thank you personally for two things. First, you taking the time to give such a thorough answer. Second, you following up concerned that your advice might not have been clear enough. I haven't been on this forum in ~10 years but it's good, no it's GREAT to see this board still has some outstanding people on it. Thank you.

Similar Threads

  1. new pads rub on rotor Elixir 5
    By guppie in forum Brake Time
    Replies: 1
    Last Post: 08-31-2012, 07:34 AM
  2. Avid Elixir CR rotor rub
    By Mr. Jimmy in forum Brake Time
    Replies: 12
    Last Post: 08-01-2012, 03:39 PM
  3. New rotor and pads for Elixir 7
    By Der Juicen in forum Brake Time
    Replies: 1
    Last Post: 02-29-2012, 08:11 AM
  4. Elixir 3's with Magura Rotor....
    By Ace5high in forum Brake Time
    Replies: 4
    Last Post: 08-29-2011, 08:46 PM
  5. XX rotor + Avid Elixir
    By marcryan27 in forum Brake Time
    Replies: 2
    Last Post: 08-26-2011, 08:54 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •