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  1. #1
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    160mm to 203mm Brake Rotor swap

    I have a Specialized Enduro 29er and am currently running a 203mm rotor on the front and a 180mm rotor on the back. I realized I have a spare 203mm rotor so I was planning on sticking it on the rear to replace the 180mm. I guess the frame is naturally built for a 160mm rotor so to get the 180mm on it there is a brake adapter.

    So before installing the 203mm rotor I bought the 203mm Shimano adapter - I tried to install the 203mm adapter, only to realize that the adapter is only meant to upgrade from 180mm to 203mm (not 160mm to 203mm). I tried double stacking the 180mm adapter and 203mm adapter, which probably would have worked but the screws weren't long enough to accomodate this.

    What is the proper way to put a 203mm rotor on a 160mm frame? Any help is much appreciated.

  2. #2
    SS Pusher Man
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    sounds like you bought the wrong adapter.
    I resolve to constantly assert my honest opinion on anything and everything - whether it is requested or not.
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  3. #3
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    Quote Originally Posted by mtnbikej View Post
    sounds like you bought the wrong adapter.
    This made your post count go up by one.
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  4. #4
    B A N N E D
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    160mm to 203mm = SM-MA-F203P/P
    180mm to 203mm = SM-MA-F203P/PM

  5. #5
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    the shimano adapter SM-MA-F203P/PM doesn't work with some brakes like hope e4. I found out the hard way.

  6. #6
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    Well of course. The shape of the adapter is designed around the shape of the caliper.

    Not surprisingly, hope has their own adapters: http://www.chainreactioncycles.com/m...r/rp-prod13728
    Quote Originally Posted by givemefive View Post
    the shimano adapter SM-MA-F203P/PM doesn't work with some brakes like hope e4. I found out the hard way.
    Sent from my XT1635-01 using Tapatalk

  7. #7
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    Frames have a maximum supported rotor size, the jump from 160 to 203 sounds like it might snap your chainstay in half under hard braking. Make sure your bike supports 203mm first.

  8. #8
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    I think you should leave the rear at 180.

    Buy a new bike with a 180 and throw the 203 on it. Problem solved.
    2017 Specialized Pitch / 2006 Specialized FSRxc / 2009 Specialized Allez

  9. #9
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    Quote Originally Posted by idividebyzero View Post
    Frames have a maximum supported rotor size, the jump from 160 to 203 sounds like it might snap your chainstay in half under hard braking. Make sure your bike supports 203mm first.
    Generally, the limit on torque for the rear wheel is the tire slipping. The force on the caliper will be higher for a smaller rotor than a larger one at the same torque. The way a caliper attaches to a frame, I believe the max torque and forces on the frame would be the same in both cases. I guess you could slam down on a hard/paved surface with the rear wheel locked and generate higher torques.

    Rear braking being limited by the tire slipping is why it is common to use smaller rotors in the rear. They give more useful control over the range of available braking. This is true for cars, motos, and bicycles.

    Front wheels and forks are different.
    Do the math.

  10. #10
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    Quote Originally Posted by eplanajr View Post
    I think you should leave the rear at 180.
    I agree. I'm seeing cost and effort here for questionable advantage.

  11. #11
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    Most riders end up braking more with the rear brake than with the front (in terms of total energy), which is why the tradition of having smaller rear rotors doesn't make too much sense
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  12. #12
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    Quote Originally Posted by mtb_phd View Post
    Most riders end up braking more with the rear brake than with the front (in terms of total energy), which is why the tradition of having smaller rear rotors doesn't make too much sense
    You wasted money on that phd of yours

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  13. #13
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    Quote Originally Posted by mtb_phd View Post
    Most riders end up braking more with the rear brake than with the front (in terms of total energy), which is why the tradition of having smaller rear rotors doesn't make too much sense
    Who told you this? May I suggest you go back and kick them in the nuts for being so wrong?

  14. #14
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    All your stopping is done with the front brake pretty much exclusively. The rear brake is just for control.

    If you're really using more rear brake than front, you're either FLYING down the trail, or you have no idea what you're doing.

  15. #15
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    Quote Originally Posted by One Pivot View Post
    All your stopping is done with the front brake pretty much exclusively. The rear brake is just for control.
    This is so right on! Most riders tend to drag their rear brake which is why rear pads wear out faster than front pads but as One Pivot states, most actually stopping (or serious slowing down) is done with the front wheel.

    Quote Originally Posted by One Pivot View Post
    If you're really using more rear brake than front, you're either FLYING down the trail or you're skidding like an idiot because you have no idea what you're doing.
    Fine tuned this statement for clarity.
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