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  1. #1
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    Choosing rotor size with new brakes

    Just got a new (to me) bike and the brakes are weak. It's a 2015 Felt Edict FRD with Avid xx brakes and a 160mm rotor. Granted, My other bike is at the other end of the spectrum with XT brakes and a 203mm rotor, but I just don't know how much bigger of a rotor I should get. I've heard that the avid brakes are generally not as powerful as the XT brakes to begin with. Im thinking that I should just go up to a 180mm rotor and see, but is that still going to feel really weak? I don't need it to feel as strong as the 203mm and XT setup, but im grabbing as much brake as I possibly can and I know I can stop faster than that. They do squeel once I start to pull pretty hard. I may have contaminated pads I guess. I just don't know what it's supposed to feel like. Oh, and I don't exactly have weak hands.

    Should have mentioned I'm 185lbs w gear. Bike is 22lbs.

    Any thoughts? Thanks!

  2. #2
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    I don't like Avids, but try and do a really good bleed on them. Than decide 180,203, or new brakes.

  3. #3
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    They don't seem spongy at all, in fact less so than my freshly bled XTs. Again, limited frame of reference with these, but they don't feel spongy. They were supposed to have been bled just before I bought it from a bike shop. Also, needing a bleed doesn't usually inhibit stopping power, just feel... Right?

  4. #4
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    Right. Bleed fixes spongy but doesn't change power, assuming lever isn't bottoming out. If you're not getting enough power, try cleaning the rotors and putting in new pads. If the rotors are clean and the pads new, try bedding them in. Properly working brakes, SRAM or Shimano, should provide plenty of braking force with one finger, even with 160 rotors.

    FWIW: I find most SRAM brakes have a firmer lever feel than XTs.
    Do the math.

  5. #5
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    With new rotor's you're just delaying the inevitable. $150 at Jenson gets you SLX brakes and you'll be set.

  6. #6
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    Quote Originally Posted by Lone Rager View Post
    Right. Bleed fixes spongy but doesn't change power, assuming lever isn't bottoming out. If you're not getting enough power, try cleaning the rotors and putting in new pads. If the rotors are clean and the pads new, try bedding them in. Properly working brakes, SRAM or Shimano, should provide plenty of braking force with one finger, even with 160 rotors.

    FWIW: I find most SRAM brakes have a firmer lever feel than XTs.
    Ok thanks. I really like the feel of them better than my XTs. I'm betting there's some lubricant or something on the rotor or pads, or the pads just aren't right.

    I'll try an alcohol cleaning on the rotor, and I heard to take a torch to the pads to burn anything off? Anyone try that?

  7. #7
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    I tried cleaning, torching and baking pads. In the end I just put new ones in.
    Do the math.

  8. #8
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    Quote Originally Posted by Lone Rager View Post
    I tried cleaning, torching and baking pads. In the end I just put new ones in.
    I've been down this road. I torched a set of pads a couple of times when I had an exploding fork on a bike - seriously, it would blow the dustcap off and spew oil everywhere, including the front brake - I did eventually get the fork fixed, and after it had proved itself fixed, I replaced the pads. Torching them and then cleaning them with alcohol helped, but they were noisy and still weren't great. Once fixed, new pads were great. In other words, unless you have a compelling reason to reuse pads that will never be as good as they should be, just buy a new set.

    Also, I would point out that unless you're planning on completely weight weenie'ing this bike out, you should just go on and put 180mm rotors on it. Your other bike runs big rotors, putting 180s on this one will bring the feel of the two a little closer together, and there are only a few limited situations where you don't want more power/larger braking surfaces, and that's where you're in a traction limited situation where the modulation available with the less powerful brake helps maintain control, ie not skid/slide.

  9. #9
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    Not sure the cost of Avid pads these days, but they used to be about $20 a set and to me that's money wasted, put a little more than that again and pick up some Deores and be done with it. I'd also upgrade to a 180 front, 160 rear is fine for that bike, your weight a proper set of brakes.
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    Bigger, faster riders build up more heat in their rotors. Up-sizing rotors for these riders (and for riders on long descents) is something to think about...

    3 reasons why you should try bigger rotors
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  11. #11
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    Quote Originally Posted by LyNx View Post
    Not sure the cost of Avid pads these days, but they used to be about $20 a set and to me that's money wasted, put a little more than that again and pick up some Deores and be done with it. I'd also upgrade to a 180 front, 160 rear is fine for that bike, your weight a proper set of brakes.
    2 pair of Truckerco are about $15 on fleabay. Of course selling the brakes themselves and replacing with Deore you'd come out ahead. On the other hand, people buying XX brakes might not be all that keen on the lack of bling factor.

  12. #12
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    Quote Originally Posted by Thumper33 View Post
    They don't seem spongy at all, in fact less so than my freshly bled XTs. Again, limited frame of reference with these, but they don't feel spongy. They were supposed to have been bled just before I bought it from a bike shop. Also, needing a bleed doesn't usually inhibit stopping power, just feel... Right?
    Yeah, if they feel firm, and they are bedded. Then I'd replace them.

  13. #13
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    Quote Originally Posted by mtb_phd View Post
    Bigger, faster riders build up more heat in their rotors. Up-sizing rotors for these riders (and for riders on long descents) is something to think about...

    3 reasons why you should try bigger rotors
    That's interesting. I went to 180 front, 160 rear many years ago (when the popular techniques was "two fingers for front brake, one for rear, to increase front brake use) and have continued to do so out of habit. I ride in the Wasatch, so the typical ride is "go up 3000 feet....go down 3000 feet". I have never experience brake fade and I usually go through front brake pads before I go through rear brake pads, so maybe I'm applying more front brake. As to squealing brakes, in my case it has always come down to misaligned pads, once requiring facing a brake mount and once requiring a replacement of the brake. In retrospect, contamination (or for that matter, "bedding"), for me, has never ended up being the cause of the noise, but after a couple of years on BB7's I've always used XT, so maybe that's another factor.

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