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I want to upgrade my mtb's front brake to a 200 or 203mm brake rotor.

current setup (180mm): enter image description here

My front fork's posts are for a 160mm rotor (without any adapters/brackets, with the brake caliper bolted directly to the fork a 160mm rotor fits). I am currently using a 160mm-180mm adapter with a 180mm rotor but would like to upgrade to 200 or 203 mm rotor.

Questions:

  • I looked online and couldn't find any (front) 160-200mm or 160-203mm adapter brackets (PM-PM). Maybe I did not look in the right places, could anyone tell me where I could get such an adapter/what to look for when buying one?
  • Or should I use a combination of two adapter brackets? (160-180mm followed by a 180-200mm or 180-203mm bolted onto the first adapter bracket) (as can be seen in the images in this thread: https://forums.mtbr.com/brake-time/160-200mm-brake-adapter-919684.html )

My setup: Fork: Rock Shocks Solo Air Spring 26"
Brake caliper (current): Magura MT4
Brake caliper (to be installed): Magura MT5

Thank you very much!

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  • You couldn’t find many 160-200mm adapters, which means you found at least one. What’s the problem?
    – Argenti Apparatus
    Jan 26, 2020 at 13:11
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    @ArgentiApparatus sorry I meant to write: I couldn't find any instead of I couldn't find many...
    – Maarten -Monica for president
    Jan 26, 2020 at 13:42
  • Are you sure that the fork will be ok with the rotor that size? I've tried to use 180 instead of 160 on 26" xc30 fork and noticed a completely unwanted vibration on the left fork leg
    – k102
    Jan 27, 2020 at 15:39
  • @k102 I will check if I can find the maximum rotor size rock shocks recommends for this fork..
    – Maarten -Monica for president
    Jan 27, 2020 at 15:46

2 Answers 2

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You need a +40mm post to post adapter. The Magura one is their part number QM42. Usually these kinds of adapters interchange between brands, but just getting the Magura one plus a Magura or Shimano 203mm rotor should set you up.

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  • Magura do a QM26 which should be a 160 - 203 PM adaptor
    – Dan K
    Jan 27, 2020 at 8:47
  • Their product desc for QM42 says "203 mm for PM 6" front mounts" and for QM26 is "203mm PM 7" fork mount". So I'm inferring that the QM26 is for 180/7" native forks. Am I missing something?
    – Nathan Knutson
    Jan 27, 2020 at 20:23
2

Using two stacked brackets to mount the caliper strikes me as being potentially dangerous.

Two components bikes together must necessarily be weaker than a single one.

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1
  • Not NECESSARILY any weaker, that depends on many factors, but I do agree with you it's not best practice.
    – Henry S
    Jan 27, 2020 at 11:38

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