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  1. #1
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    rotor size/rider weight correlation

    I'm 140lb, riding a 5" trail bike. Does the 160/140 make sense, or would 180/140 or 180/160 make more sense with braking lever bias? I was going to be using alligator rotors.

  2. #2
    Bearded highlighter
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    I would have to say that 160 F/R would work better but hoepfully more experienced riders will chime in

  3. #3
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    140mm seems kind of over (under?) the top for me...

    I weigh 140 ride a 5" trail bike and currently setup as 160F/R...no complaints, I have plenty of stopping power and heat doesn't seem like a problem. If I choose to upgrade rotors in the future I'll be running 180/160. But as for now they work.
    Last edited by Renovatio; 11-19-2008 at 12:11 PM.

  4. #4
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    I'd run a 26" rotor if i could still turn left with it mounted...
    Hell is eternally climbing manzanita trail on your singlespeed.

  5. #5
    I AM I AM
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    Well I'm about 150lb and I find shimano XT's with 160 / 160 rotors ample, even for DH tracks I'm starting to ride, and being a beginner it means brakes on a lot!

    It depends on the type of brakes you have too. Shimano's are known to have great modulation and ample power. You may possibly need bigger rotors if you have low end brakes (say something like Hayes Sole for example) compared to a higer end set.

    There is no rule - if your brakes are overheating or fading you go for bigger rotors, if not then stick with what you've got.

    If you mostly do xc on your trail bike then 160/140 may be a good option. Also something to consider is how much you actually use the rear brake? Some people use the front more, I like using my rear more or equally as the front, maybe you use both equally. A lot of factors involved.

  6. #6
    huffin' n' puffin'
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    Quote Originally Posted by Kyle2834
    I'm 140lb, riding a 5" trail bike. Does the 160/140 make sense, or would 180/140 or 180/160 make more sense with braking lever bias? I was going to be using alligator rotors.
    What kind of riding are you doing? XC? Aggressive XC? Downhill? etc

  7. #7
    OSCMTB
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    I'm between 150 and 160 depending on the season and I run 180F/160R. I could get away with 160 F/R but prefer the ample power that the 180 gives me. I ride aggressive XC, FWIW

  8. #8
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    I am trying to decide on rotors as well... Is there such a thing as a rotor being too big?..

  9. #9
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    Quote Originally Posted by scottzg
    I'd run a 26" rotor if i could still turn left with it mounted...

    You CAN run a 26" rotor. It's called v-brakes

  10. #10
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    Quote Originally Posted by ALLMOUNTAIN18
    I am trying to decide on rotors as well... Is there such a thing as a rotor being too big?..
    Yea. If your rotors are bigger than you need, you will lose modulation, meaning the brakes will feel "on/off" with no in between.
    You really want to be able to feel the brakes and apply more lever as more power is needed.....too big a rotor will make this hard to do.

    It depends on a few factors. Weight, riding style and the brake type.
    Look, whatever happens, don't fight the mountain.

  11. #11
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    I've found that larger rotors give me more modulation. Sure, they take less pressure to lock but I can balance it on the verge of locking much easier and more precise. I'm running 203 in the front and 185 in the rear. I would've gone with a 203 in the rear if it would fit just for the modulation.

  12. #12
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    Quote Originally Posted by savagemann
    Yea. If your rotors are bigger than you need, you will lose modulation, meaning the brakes will feel "on/off" with no in between.
    You really want to be able to feel the brakes and apply more lever as more power is needed.....too big a rotor will make this hard to do.

    It depends on a few factors. Weight, riding style and the brake type.
    Quote Originally Posted by BuickGN
    I've found that larger rotors give me more modulation. Sure, they take less pressure to lock but I can balance it on the verge of locking much easier and more precise. I'm running 203 in the front and 185 in the rear. I would've gone with a 203 in the rear if it would fit just for the modulation.
    Can anyone confirm which is correct?..

    Thanks..

  13. #13
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    Quote Originally Posted by ALLMOUNTAIN18
    Can anyone confirm which is correct?..

    Thanks..
    The majority here will disagree with me but this is my experience.

    With more leverage of the big rotor it just gives you a more precise feeling. Sure, if you just squeeze the lever without thinking it will lock up easier.

    Besides, I want overkill on my brakes. Why settle for adequate. There's not much difference in price between the big and small brakes of each brand and I'm not concerned with a couple ounces of weight on a mountain bike. Will I ever *need* the big brakes? Not often but I like knowing I will never run into brake fade. Think about it, we don't settle for brake fade on our cars yet we run brakes on our bikes that have the potential to fail during normal use.

  14. #14
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    I kind of agree with Buick GN (what year GN) on this one. I have a FS Trek that is pretty heavy 21.5 " frame with 2.30 rubber fnt and rear, while the stock Hayes brakes are okay for most riding. I have run into situations when I just needed more brake. I recently ordered a new bike, am expecting it on Dec 2nd. It was speced with Juicy 203mm. Most would say it is over kill, but as previously mentioned above, I can learn to be more judicial on the lever, and so what, what is a few ounces when you are talking about a 29-30# AM bike?

  15. #15
    Double-metric mtb man
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    It depends on the brake a bit (if it can tolerate the change without a noticible effect on modulation), but from a physics point fo view, you'll generally lose some modulation with a larger rotor.

    If it helps any, I'm a bigger guy (235+ gear) and run 4 caliper brakes, 203 mm front and 180 rear. My set-up is intended for the best modulation I can get while getting one-finger lock-up power on asphalt if I need it.
    As if four times wasn't enough-> Psycho Mike's 2013 Ride to Conquer Cancer Page

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  16. #16
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    Would you guys recommend going with a larger front rotor or same front and rear rotor size?

  17. #17
    ~Disc~Golf~
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    don't forget to check your max. rotor size recommended for your fork.
    i also agree w/ 'buick'. i run 185mm bb7's f/r. i can 'de-tune' the rear at the lever a bit to get the bias correct. plus, i have 'swapability' in case i catastrophically damage a rotor on the trail
    Honestly, you just take a deep breath and say Fuck it.

  18. #18
    trail addict
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    Quote Originally Posted by ALLMOUNTAIN18
    Can anyone confirm which is correct?..

    Thanks..
    Brake modulation is a result of the type of brakes used and types of pads. It has to do with how the force from your fingers is transferred to force at the rotor.

    The SIZE of the rotors will affect the mechanical advantage of the forces in brake system from the rotor to the tire (mis-named "power" frequently, but when people refer to the "power of their brakes", we know what they mean).

    To make matters worse, modulation is very subjective, so what one rider considers "good modulation" may feel lousy to someone else.

    The correct answer to your question is that you will get good modulation by using a good set of brakes with adequate sized rotors and appropriate pads for your weight/riding style.
    You better just go ahead and drop that seatpost down to the reflector... the trail gets pretty rough down there.

  19. #19
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    I vote 180mm F/160mm R as a good AM combo.

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