brake rotors have a 'burnt' colour - why?

jamescrampton17
jamescrampton17 Posts: 19
in Workshop
Came back after a ride yesterday to notice that my rear brake rotor has got this burnt orange look to it and im not sure why? any pointers?

There was a reasonable amount of fast downhill and being a new route and not knowing exactly what was coming up , would say I spent more time than usual on the rear brake just keeping it steady

Comments

  • lesfirth
    lesfirth Posts: 1,382
    Probably because it has been hot. :)
  • jamescrampton17
    jamescrampton17 Posts: 19
    yeah that's what I was thinking. was just wondering if it was something that needed to be looked into or not
  • ugo.santalucia
    ugo.santalucia Posts: 28,312
    No, nothing to worry about, it just shows you are badass
    left the forum March 2023
  • davidof
    davidof Posts: 3,116
    Be careful, your rotors have been tempered in the heat which makes them brittle and theyand may shatter next time you use them
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  • lesfirth
    lesfirth Posts: 1,382
    davidof said:

    Be careful, your rotors have been tempered in the heat which makes them brittle and they and may shatter next time you use them

    I am no metallurgist but from my scant knowledge. If the OP has heated his discs to cherry red temperature and then thrown his bike in a pond before they cooled he might have altered the temper of the discs.
    If he has got the discs that hot and then let them cool naturally the discs might be softer and less likely to shatter.
    I remember watching rally cars on night stages. Their front discs were bright orange hot, repeatedly. It was never a problem.
  • ballysmate
    ballysmate Posts: 15,930
    lesfirth said:

    davidof said:

    Be careful, your rotors have been tempered in the heat which makes them brittle and they and may shatter next time you use them

    I am no metallurgist but from my scant knowledge. If the OP has heated his discs to cherry red temperature and then thrown his bike in a pond before they cooled he might have altered the temper of the discs.
    If he has got the discs that hot and then let them cool naturally the discs might be softer and less likely to shatter.
    I remember watching rally cars on night stages. Their front discs were bright orange hot, repeatedly. It was never a problem.
    But if they are Shimano, according to the other thread, they may be made of cheese.
  • thistle_
    thistle_ Posts: 7,218
    I've never seen rotors go a burnt orange colour from heat, that's usually rust :smile:
    Mine have gone that bluey-purple colour occasionally from overheating.

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