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  1. #1
    ride hard or die
    Join Date
    Mar 2004

    swapping out rotors when replacing pads

    Just came to a realazation this weekand. I swapped out my brake pads for my juicy 5's. Stopping power increased dramaticly, but not how it felt when I first bought the brakes.
    I swear on everything I can feel my rotors loosing grip. Then I read somewere that you should swap out the rotors everytime you swap out the pads. What do you all have to say about this. Do you folllow this unoficial rule?

  2. #2
    mtbr member
    Join Date
    Jul 2007
    no. to be honest I think that is a ridiculous & expensive proposition. If I change the rotors I will put on new pads but not the other way round.

    Try cleaning your discs with isopropyl alcohol.

    Are you running different types pads to the oem items? If not then that could easily account for any differences you feel when braking.

    It could also just be your imagination.

  3. #3
    Reputation: Jerk_Chicken's Avatar
    Join Date
    Oct 2005
    You don't swap rotors out with every pad swap. I've never seen that said before.

    All it takes is some time for the face of the pads and rotors, whether old or new, to wear into one another. Different manufacturers have different procedures, but in general the following applies to all:

    Wash the pads and rotors thoroughly with alcohol.

    It helps with new and old pads to slightly remove a bit of the surface by adding some alcohol between two pads and rubbing them together.

    Extreme cases may just require a light sanding and nothing more.

    As far as your quote about "on everything, I can feel my rotors losing grip", I'm curious to know exactly what is being experienced. It's just a curious statement because how do you know it's not the pads? How do you know that your brakes simply need more time to wear into one another? Then over trail features, you're losing your brakes? If that is true, then something else is severely wrong with the setup.

  4. #4
    mtbr member
    Join Date
    Sep 2008
    No you shouldn't replace disks, just clean them, an explanation is below. Also different pads have different temperature ranges and coefficients of friction, which can modify the stopping ability of the brakes.

    Bike disks work the same as car disks, pad material is transferred to the rotor when it gets hot and then when you brake, the transferred material and the pad wear away instead of the pad wearing away with the rotor. That is why rotors last so much longer than pads. The catch to this scenario is that certain types of pads, semi-metallic usually, have a higher transfer temperature, and will thus wear down on rotors if they are used cold. This happens since the pads never get hot enough to produce a transfer layer on the rotors. This is also why you "bed pads in", to produce this layer. In cars when we switch from one type of pad to another, we normally have to clean the old pad transfer layer off using a racing brake pad, has a high transfer temperature, at a cold temperature that basically acts like sandpaper on the rotors. For bikes the same thing applies except we can use alcohol to so this most of the time. If that doesn't work use sandpaper to rub of the top layer.

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