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2 days ago after the last ride my front rotor (Ashima AiRotor 203mm) twisted again in a small area on it (not hit in obstacle or overheated), I was almost ready to throw another half an hour from my life to manual truing it with the tool, but gave up and decided to ask the community what is the idea to true it with best results and doesn't last 4-5 rides before twist again. Note that the brake caliper is centered so there's almost a symmetrical gaps between the rotor and brake pads and both brake pistons go out also symmetrically. Is it worth it to remove the rotor from the hub, heat it to mineral oil's boiling temp and put it on a press with 2-3t pressure or put it on lathe and use a pushing rollers on 1/3 of it's braking surface, like in machines which straightens the steel wire?

Thanks in advance

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    I had to google for what these things are, and the first hit says that they twist easily and "It turns out that the reason for the warping was running the rotors wrong direction, so they have returned to the original style and specify to run them in the normal rotor direction." – ojs Nov 19 '17 at 9:43
  • Well, that was the initial idea in our LBS - to flip it at wrong side so we test if it will unwarp, for this reason we picked for testing another rotor from the same model/size but apparently this alloy doesn't allow that :( They (in this case Ashima) incorporated in the desing somewhat a passive ABS braking mode, easily notified by the clear Bzzz! sound, almost like a bee near your head :) Especially on a brand new rotor – 1000Gbps Nov 19 '17 at 10:28
  • @ojs You are right! Seems the old ones and the new which I have must be flipped at 180 so they stop twisting – 1000Gbps Nov 19 '17 at 20:27
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Your best and safest option is to replace the rotor with a new one.

Bend metal enough and it will deform permanently.

In addition, rotors do wear away slowly over time. There's a chance yours is getting thinner, and more vulnerable to bending. Generally they're ~2 mm thick when new and unservicable at 1.6 mm thick.

Finally, if your rotor has overheated at any time (IE its blue or rainbow-coloured) then the rotor has also been weakened and is vulnerable to bending and warping.

Brake systems are the one part on which you don't want to cheap-out.

  • Yep for the thickness, measured them at ~1.84mm front and ~1.725mm rear because each month in the active season I'm swapping front with the rear if there's a 3% diff – 1000Gbps Nov 19 '17 at 7:41
  • Anyway I'm on the idea that there's a chance this specific rotor is made from alloy sheet with below the standard characteristics, though this is one of the best monolith rotor designs that allows to be used with any type of pads (as stated by the manufacturer) – 1000Gbps Nov 19 '17 at 7:47
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    Decided to replace the rotor - safest option, as always – 1000Gbps Nov 21 '17 at 22:55
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    @1000Gbps Good work. The old rotor can now be upcycled as modern art, a ninja throwing star, or some other piece of useful gadgetry :) – Criggie Nov 22 '17 at 6:55
  • Because in general this is a very strong material and surprisingly in a very optimised form, I'll use it as a frame for a custom quad or hexacopter – 1000Gbps Nov 22 '17 at 16:20

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