Braking Question- Mtbr.com
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  1. #1
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    Braking Question

    I was out on a long ride yesterday and found a really steep downhill road section which lasted for about a mile or so. After the ride my bike computer said I’d got to just over 48mph as my max speed, a new record for me.

    My Louise 07’s handled hard braking from this speed excellently, and in fact later in the ride my front brake seemed to be performing a lot better. When I got home I noticed that my front rotor (SL 180mm) had changed colour to a very slightly blue’ish shade where the brake pads contact the rotor. I hope there’s nothing now wrong with the brake pads and rotor as they are performing better than ever!

    Have I over cooked my brake pads and rotor? Should I be concerned about the rotor’s colour change as it seems to imply very high temperatures have tempered it Will there be wear rate issues as a result?

    Thanks in advance for any advice

  2. #2
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    Its like when an exhaust pipe gets hot and changes color. Probably nothing to worry about, but be careful going almost 50mph on the road (on a mtb i'm assuming)

  3. #3
    I-S
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    The better performance is because you have now properly bedded in the pads to the rotor.

    A little bit of blueing is not a problem. If it keeps happening, however, you should look at getting a bigger rotor.

  4. #4
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    Agreed. Heat discoloration is only an indication of past abuses, but not necessarily an indicator of rotor or pad damage.

    Keep riding, but if you find you overheat them regularly, a larger or bulkier rotor is in order.

    Note that not all 180mm rotors are created equally. I've seen some that look waifish, using minimal material to keep weight down. Note that the Avid 185 <i>Clean Sweep</i> in the photo below had 2x the number of spokes as the badly discolored 165mm rotor it replaced, plus the second "hub." I'm convinced this extra material was more important for me than the extra diameter: the smaller rotor had enough power, it just overheated too often.

    <img src="http://www.booboodog.net/images/185(3).jpg" width="400">
    speedub.nate
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  5. #5
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    RedBlueGreen.....

    a picture would be nice. But I doubt that you'll have any issues as the others have said. You brakes are performing better because, as the others have said, you'be bedded them in. Bedding in takes place as you use the brakes. A slight amount of brake pad material is deposited on the rotors and the pads also scrub the rotors smooth. This increase the grip that the pads have on the rotors. The deposited pad material (depending on the pads) can give the braking track on the rotor a slightly bluish tint that has nothing to do with heat discoloration. Heat discoloration is usually a bit darker and is not usually restricted just to the braking track. We'd have to see a picture to tell you for sure. But even if there is a bit of heat coloring on the rotor, it shouldn't be a problem as long as it is not severe. So unless you are looking at a heavy blue/black discoloration that's kind of brownish around the edges don't sweat it.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  6. #6
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    Thanks for all your replies, I'm grateful.

    Your points are all very interesting because I thought I'd already completed bedding in my rotors and pads a few months ago! I've done as Magura recommend and performed over 30x 30kmh strong stops...and have done many more since then. I guess that wasn't enough, or I didn't do it right. I'm running SL 180 rotors front and rear on a hard tail.

    My Magura pads (6.1 performance) have what looks like golden shreds of metal in them, so I'm not sure about the blue tinge from the pad material being deposited on the rotor, but of course you may very well be correct Squash. The blueing colour is only a slight tinge so as mentioned in your thread replies it hopefully won't be a problem. I now notice that since my ride yesterday the rear rotor has also developed a blueish tinge, albeit slightly less pronounced than the front.

    My concern was that if the rotor had been tempered it might have altered its future wear characteristics.

    One thing that has impressed me about the higher speed braking experience is that my brakes seem like they have 10% or so more power...well, in the front brake at least. It certainly seems more strong now. I'd describe it as controllably grabby, almost fierce. It's kind of like the braking's come alive from what was already a superb brake.

    Please note, from a safety perspective I'm certainly not advocating everyone doing high speed hard braking maneuvers to get their brakes to perform as they'd hope!

    But in my mind it does bring into question the bedding in process as recommended to get optimal braking performance. How could I have done it better? How have I not achieved what the manufacturer describes clearly in their instruction manual within the bedding process?

    I already had a lot of respect for my Louise 07's but having them perform like they are now is astounding.

  7. #7
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    So, is this a overheated rotor?


  8. #8
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    Quote Originally Posted by liquidtiger720
    So, is this a overheated rotor?
    That looks pretty normal to me... "used, not abused."

    The 165 that I definitely overheated took on a rainbow color effect all the way down the spokes, towards the hub. It was a pleasing effect, like you would find on the polished exhaust stack of an old warbird or a Harley.
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  9. #9
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    liquidtiger720, my rotors don't look anywhere near as blued as yours. Could I ask you...

    Did the colouration appear in a particular situation or over a period of time?
    Was there any change in braking performance as a result?
    Are you using Sintered Pads?

    Thanks in advance.

  10. #10
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    Yeah they look...

    well used, but pretty much normal.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  11. #11
    2007 kona stuff
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    are those spokes brownish from overheating, or is that just the reflection, look nothing like my discs
    try or die

  12. #12
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    I actually just got the bike RBG. I took it down some steep hills around San Francisco where I had to keep speeds slow because of cross traffic not having stops. Of course, being the newb I am, dragged the rear brake around. I didn't feel any difference in performance. As far as having sintered pads, I have no clue. Sorry. If it helps, the picture is of the brakes on a stock 07' jamis durango 2.0 .


    Dalton, yes...the brownish spokes are there, not a reflection.

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