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  1. #1
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    20 inch brakes wtf?? *pic*

    so i was arguing with my friend about how only 12 inch rotors are currently avaliable and he shows me this pic...i think its quite pointless as no body needs that kind of stopping power.

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  2. #2
    fitter, happier Ronin's Avatar
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    And not to mention it's on the rear wheel.

  3. #3
    close to 2000 madbiker555's Avatar
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    Hahah I was actually going to start a thread on this. I dont get it.

  4. #4
    Senior Member zx108's Avatar
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    that looks rediculas.

  5. #5
    blithering idiot jhota's Avatar
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    uhm, on a trials bike like that, don't you want massive rear holding power? same idea as Magura hydro rim brakes, right?

  6. #6
    Giggity giggity! Dirtbike's Avatar
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    That looks like the ultimate trials brake.
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  7. #7
    Senior Member Kustomz's Avatar
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    Bend a wheel, bend a rotor......

  8. #8
    Señor Member USAZorro's Avatar
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    butt ugly
    The search for inner peace continues...

  9. #9
    (Grouchy)
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    i don't really understand what the difference between that and just a regular magura rim brake would be. for trials riding, i don't see an advantage to having disc brakes.

  10. #10
    Just Ride
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    I wonder if it does have great stopping power? But it looks stupid IMO.

  11. #11
    Norcal 29er
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    Quote Originally Posted by xenochimera
    so i was arguing with my friend about how only 12 inch rotors are currently avaliable
    Okay, correct me if I'm wrong, but where do you see a 12 inch rotor readily avalible? Isn't 203mm the biggest made? Am I the only one who thinks this is weird? What is love? Where is the bathroom? When will they pass the bong?!?!?!


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  12. #12
    Giggity giggity! Dirtbike's Avatar
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    Quote Originally Posted by OneTinSloth
    i don't really understand what the difference between that and just a regular magura rim brake would be. for trials riding, i don't see an advantage to having disc brakes.
    In a hydraulic brake, the leverage creates a large amount of pressure at the caliper. Take the amount of pressure it takes to stop you with a caliper and a 6 inch rotor, and put the same caliper on a rotor that is probably 20 inches in diameter, thats alot of power. The pressure on rim-brake pads is not nearly as much, even with the HS-33's. With this brake, its probably either free or locked.
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  13. #13
    Ride bike or bike ride? Hopper's Avatar
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    That is bloody stupid. For a trials bike you wat either on or off, ok big brake yay. The only advantage a trials bike could gain from a disc brake is that the braking surface is not effected by the shape of the rim. The rim actually flexes quite alot no matter how strong the wheel. Now this has lost the advantage.

    Also this set up is going to be heavy compared to hydraulic V brakes (arguably the best thing for trials, lots of power and lighter than discs) another problem with discs in trials is the forces sent through the caliper has been known to rip the brake mounts off a frame.

    Finally, the main reason 8 inch rotors have better stopping capability over 6 inch is not the distance from the axel (that helps a bit but is not the main reason). The main reason is a larger surface to dissipate heat! The rotor can cool down better, the brakes don't over heat and voila..... better braking performance. Now on a trials bike there is no draggin of the brakes, therefore little there is little heat created so no need for large surface.
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  14. #14
    Flatland hack Flak's Avatar
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    The larger diamater creates better leverage, thus better braking?

  15. #15
    I drink your MILKSHAKE Raiyn's Avatar
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    Ancient picture of an old show bike.

  16. #16
    Senior Member MattBeaty's Avatar
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    Quote Originally Posted by Flak
    The larger diamater creates better leverage, thus better braking?
    Exactly, let me put it into a different perspective. The friction between the pad and the rotor is always parallel with the rotor. You could say that the friction between the pad and the rotor was like a hand pushing on the end of a wrench trying to turn it. Now imagine you had a really stubborn bolt (covered deeply enough in another thread) would you want a long wrench or a short wrench. Of course you would want a long wrench. The same thing applies for brakes. The longer the lever arm, the greater the stopping power from the same amount of frictional force.

  17. #17
    Lost in the Black Hills mx_599's Avatar
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    Quote Originally Posted by MattBeaty
    The longer the lever arm, the greater the stopping power from the same amount of frictional force.
    ...the greater the stopping power due to an increased amount of frictional force.

  18. #18
    Senior Member MattBeaty's Avatar
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    Quote Originally Posted by mx_599
    ...the greater the stopping power due to an increased amount of frictional force.

    The frictional force would not change, kinetic friction is defined as the coefficient of kinetic friction x the normal force. The coefficient of friction is derived from the properties of the materials (not changing, regardless of the size and shape of the brakes and pads) The normal force is simply the squeezing power of the brakes,, also doesn't change when the rotors size changes. The only difference is the lever warm, which is why the braking power increases. Also the increased mass would prevent overheating the brakes, but the main difference would be the increased lever arm.

  19. #19
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    Quote Originally Posted by MattBeaty
    Exactly, let me put it into a different perspective. The friction between the pad and the rotor is always parallel with the rotor. You could say that the friction between the pad and the rotor was like a hand pushing on the end of a wrench trying to turn it. Now imagine you had a really stubborn bolt (covered deeply enough in another thread) would you want a long wrench or a short wrench. Of course you would want a long wrench. The same thing applies for brakes. The longer the lever arm, the greater the stopping power from the same amount of frictional force.
    Yes its called torque.

  20. #20
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    Quote Originally Posted by MattBeaty
    Exactly, let me put it into a different perspective. The friction between the pad and the rotor is always parallel with the rotor. You could say that the friction between the pad and the rotor was like a hand pushing on the end of a wrench trying to turn it. Now imagine you had a really stubborn bolt (covered deeply enough in another thread) would you want a long wrench or a short wrench. Of course you would want a long wrench. The same thing applies for brakes. The longer the lever arm, the greater the stopping power from the same amount of frictional force.

    yes, its called torque. For a given force (the friction of the brake) the stopping power increases as the length of the moment arm (radius of rotor) increases. If there is also more friction due to surface area, that is just another added bonus.
    pretty soon they might even put the brakes on the rim... crazy!

  21. #21
    Senior Member MattBeaty's Avatar
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    Quote Originally Posted by MattBeaty
    The only difference is the lever warm, which is why the braking power increases. Also the increased mass would prevent overheating the brakes, but the main difference would be the increased lever arm.
    The above should say lever arm, not warm. For some reason I can not edit the pst it is saying that the thread does not even exist.

  22. #22
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    Quote Originally Posted by MattBeaty
    The frictional force would not change, kinetic friction is defined as the coefficient of kinetic friction x the normal force. The coefficient of friction is derived from the properties of the materials (not changing, regardless of the size and shape of the brakes and pads) The normal force is simply the squeezing power of the brakes,, also doesn't change when the rotors size changes. The only difference is the lever warm, which is why the braking power increases. Also the increased mass would prevent overheating the brakes, but the main difference would be the increased lever arm.
    holy crap
    dude, are you like an engineer or something?
    wow you must be REALLY smart
    as for the brakes... i wouldnt have 20" disc(s)
    i hardly use my 6" rotors to the max
    Trance music is okay...
    Drum & Bass is way better

  23. #23
    Svr
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    Senior Member Svr's Avatar
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    A similar setup has been used on the front wheel of Buell motorcycles for the past few years.

  24. #24
    Flatland hack Flak's Avatar
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    pretty soon they might even put the brakes on the rim... crazy!
    That right there just made this thread worth reading

  25. #25
    Senior Member MattBeaty's Avatar
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    Quote Originally Posted by FF 6800
    holy crap
    dude, are you like an engineer or something?
    wow you must be REALLY smart
    as for the brakes... i wouldnt have 20" disc(s)
    i hardly use my 6" rotors to the max
    I am an engineering student. That is the only rason that the Physics and Statics are fresh in my mind.
    Last edited by MattBeaty; 01-16-06 at 03:41 PM.

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