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  1. #1
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    Pulsing Avid Elixir 9

    I know there are already a few threads on this, but I want to add my observations. I have Avid Elixir 9, new this year, 180mm front, 160mm rear, new this spring. The brakes have been reliable and predictable, and have performed well. Last night I did a race in the pouring rain - 60 minutes of racing in continuous intense downpour. I was a little disappointed with the change in braking performance in the extreme wet - there were times I needed full squeeze strength to get the stopping power I wanted. That doesn't bother me too much, of course the braking power will be affected in extreme wet.
    More of a concern is the new pulsing in the front brake. The pads grab very hard on the part of the rotor where the spider connects to the braking surface, and almost not at all between the spiders (without changing the force on the lever). I suspect that either the rotor has worn so that the braking surface is now a little thinner than the spider, or the pads have worn uneven so that there is less pad on the main part of the braking surface, and relatively more pad toward the inside where the braking surface meets the spider. I can see that the pad does go onto the spider, based on the wear lines on the rotor.
    I happen to have a brand new rotor, so I'm going to try swapping out the rotor. I also have less worn pads (on the rear) that I can swap out. I'm going to try both when I get a chance to spend more time on this, and I'll post my results.
    I've also seen reports of people adding spacers to move the caliper out a bit to prevent braking on the spider. Any thoughts on this? It is a stock setup, I would have expected the alignment to be correct, but I can see that the pad drags on the spider more that I think it should.
    Richard.

  2. #2
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    pulsing is caused by inconsistent grab of the pads on the rotors. quite a few caused. I'd clean the rotors, sand the pads and re break-in the system for starters.

  3. #3
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    Quote Originally Posted by bing! View Post
    pulsing is caused by inconsistent grab of the pads on the rotors. quite a few caused. I'd clean the rotors, sand the pads and re break-in the system for starters.
    OK, I'll start there. To clean the rotors: I have a can of brake cleaner - is that better than isopropyl alcohol, or is the alcohol recommended?
    Thanks,
    Richard.

  4. #4
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    either one will work. you just want to make sure the rotor surface is as clean as you can get it.

    The pads should not be coming into contact with the rotor arms; only the outer ring. Check to make sure you are using the correct adapter for those brakes/bike frame. If that is all good, then you can try and add necessary spacers to move the caliper out a little so that the pads do not contact the rotor arms. You should also check your pads as they may have uneven wear and may need replaced once you get your caliper properly set.
    2008 Trek Fuel EX 8

  5. #5
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    Quote Originally Posted by Jetta2010 View Post
    The pads should not be coming into contact with the rotor arms; only the outer ring. Check to make sure you are using the correct adapter for those brakes/bike frame. If that is all good, then you can try and add necessary spacers to move the caliper out a little so that the pads do not contact the rotor arms. You should also check your pads as they may have uneven wear and may need replaced once you get your caliper properly set.
    As far as I can tell it is the correct adapter, it came stock on the bike (Scott Scale 29er Pro). I took the bike out of the box myself, so it is for sure that is the setup Scott shipped it with. But the pad is definitely contacting the arms. I'll post a picture when I get home tonight. What sort of spacers to use? There were none in the bike kit, but I have lots of spacer-like things kicking around, so I'll try to fit something in there. And yes, I figure I'll have to replace the pads if I do end up changing the caliper position.
    Thanks,
    Richard.

  6. #6
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    Brake cleaner works better. A little care is needed though. Use gloves, spray outdoors and dont get them in the hub bearings.

    Then a proper break-in is essential. It will squeal for starters, but that will burn off breaking in.
    Last edited by bing!; 06-07-2012 at 02:46 PM.

  7. #7
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    Quote Originally Posted by Jetta2010 View Post
    The pads should not be coming into contact with the rotor arms; only the outer ring.
    The avid 7 inch rotors do that for years (roundagon, g2, g3, hs1 - not the 6 and 8 inch ones for some reason). They have a smaller brake track and cause much trouble.

  8. #8
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    Pictures attached. These are HS1 rotors, they came stock with the Elixir 9s. The brake track is not actually round, it has wave to it. The pad extends beyond the outer edge of the track, as well as makes contact with the spider arms. The brake definitely grabs harder at when the spider arms pass through the caliper, the difference in force is great and that makes it easy to determine where it is grabbing.
    Attached Thumbnails Attached Thumbnails Pulsing Avid Elixir 9-dsc00804.jpg  

    Pulsing Avid Elixir 9-dsc00809.jpg  


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