160mm to 203mm conversion???- Mtbr.com
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  1. #1
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    160mm to 203mm conversion???

    I am trying to change my 160mm front rotor to 203mm. I have the Shimano BR-M575 brakes and a SR Suntour XTC 29" fork (stock Giant Talon 29er fork). I ordered

    "Magura Adaptor QM7 203mm rotor with front PM 6" mounts"

    Off of eBay. I got it today and am pretty sure I bought the wrong adapter. Any info on the correct adapter and where to get it would be great. Thanks.

  2. #2
    transmitter~receiver
    Reputation: meltingfeather's Avatar
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    You're right, that's the wrong adapter. It is for post mount (PM) brakes and a PM fork.

    That fork looks like it has IS mounts (tapped holes facing sideways). Your brakes are PM (tapped holes facing rearward). The adapter you need will look something like this (with a combination of sideways and rearward facing holes):


    Or since you like eBay, I found this.

    NOTE:
    From the Suntour website specs for the XCT V3 100 29" fork:
    max. disc diameter 160mm
    Last edited by meltingfeather; 01-03-2011 at 05:08 PM.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  3. #3
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    I too saw that on the Suntour website that max disc size is 160mm. I guess I really don't get how the fork determines the size of the rotor.

  4. #4
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    Quote Originally Posted by Camdonite
    I too saw that on the Suntour website that max disc size is 160mm. I guess I really don't get how the fork determines the size of the rotor.
    The braking load is applied to the fork leg. A larger rotor allows you to make harder, faster stops.
    For the same stop, however, a 200mm rotor will apply less force than a 160.
    Quote Originally Posted by pvd
    Time to stop believing the hype and start doing some science.
    29er Tire Weight Database

  5. #5
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    Quote Originally Posted by Camdonite
    I too saw that on the Suntour website that max disc size is 160mm. I guess I really don't get how the fork determines the size of the rotor.
    Braking puts a lot of "force" on the leg of the fork. They twist the leg if you look down the fork leg while braking you can sometimes see this.
    Some say that a 200mm rotor brake combo will twist a qr out of the wheel others disagree.
    If you look at the forks that can use 200mm rotors they are big diameter legs or double crown.
    If the manufacturer recommends a size thats what I would stick to. Otherwise the common advice is 180mm max for qr axles again others disagree. YMMV
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

  6. #6
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    Thanks for the help. That just gives me a reason to upgrade my fork!

  7. #7
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    Quote Originally Posted by Camdonite
    I too saw that on the Suntour website that max disc size is 160mm. I guess I really don't get how the fork determines the size of the rotor.
    The fork might not be designed to handle the added stress an 8" rotor exerts. Also, might have clerence issues with a 8" rotor.

  8. #8
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    shimano-disc-brake-calliper-adapter/ you can get tehm anywhere
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

  9. #9
    Carbon & Ti rule
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    [QUOTE=mitzikatzi]Braking puts a lot of "force" on the leg of the fork. They twist the leg if you look down the fork leg while braking you can sometimes see this.

    Not as much force as the tree you hit if you don't brake or look down when you shouldn't.

    FWIW Also anyone that buts a 200 size rotor on a QR type fork also opens them self up for alot of brake rub as the fork flex's
    I have a 6 Berth & 2 Berth Motorhomes that I rent out . They are based in Tauranga, New Zealand

  10. #10
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    the old double post had me confused
    Duct tape iz like teh Force. It has a Lite side and a Dark side and it holdz the Universe together.

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