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Why should I bed in my disc brake pads and what's the best way to do it?

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    What does "bedding" mean?
    – Goodbye Stack Exchange
    Commented Nov 23, 2010 at 19:59
  • is this like "toe in" on normal brake pads?
    – dotjoe
    Commented Nov 23, 2010 at 21:16
  • @dotjoe No. Toe in refers to an angular measurement in the installation process.
    – Brian Knoblauch
    Commented Nov 24, 2010 at 15:24
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    Nevermind...bed in simply means to "break in".
    – dotjoe
    Commented Nov 24, 2010 at 15:40
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    Bedding brakes should only be done in the privacy of your home. Remember, a gentleman never tells!
    – Daniel R Hicks
    Commented Mar 2, 2012 at 19:31

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Bedding in brakes removes any glaze from your new pads, and any contamination from your disc rotors. It also transfers material from the pads onto the rotors, which helps them work together. It's essential to get the optimum performance from your brakes when you change pads. Follow these steps:

  1. Clean your rotors - you don't want them to transfer any grease and grime to your new pads. You can buy dedicated brake cleaner.

  2. Fit the new pads and find a place where you can build up a bit of speed. A hill is helpful for this.

  3. Build up some speed and then brake to a gradual halt. Repeat a few times.

That's probably all you need to do. However some people, myself included, like to pour water over the hot brakes. I'm not sure this actually improves anything but even if it doesn't it sizzles and steams, which is pretty cool

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    By pouring water, you are effectively qunching the rotors. Although I suspect the temperature is not high enough for any noticeable changes.
    – Vorac
    Commented Feb 4, 2015 at 8:25
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The reason you need to bed in your pads is so that they contact the disc rotor evenly. Even if you think you've set them up perfectly, the rotor and the pad are very hard and when you apply the brakes initially there is not going to be completely even contact between pad and rotor. By bedding them in, you're effectively wearing away the top layer of the disc rotor so you get completely even contact.

To do this you simply need to brake hard, generating heat and wear. I find sprinting down the road and put the front brakes on hard, whilst keeping my weight well back to prevent an embarrassing endo, works well. For the rear I again sprint off but then apply it steadily and firmly, also with weight well back and just enough pressure to brake hard without skidding. It helps if you're on a really grippy surface like tarmac.

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    bedding in pads -whether on a car, motorbike or bicycle should be done with firm pressure not slamming them on.
    – Mauro
    Commented Nov 25, 2010 at 12:19
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    @Mauro It depends on the manufacturer. Really need to check the instructions for whatever pads you use. On my car, I've had some that say "drive real easy, light braking only", others that say "drive normal, but try not to overheat", and the current set says "do repeated maximum effort braking from 60mph until you can smell them, then drive without stopping for 5 minutes to allow them to cool".
    – Brian Knoblauch
    Commented Nov 29, 2010 at 14:19
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Bedding in is a term applied to most metallic braking devices. Pads and rotors/discs wear at different rates and can end up slightly grooved depending on the natural variations in the pad/disc materials. when replacing one or the other or both items you need to bed them in to ensure that both surfaces conform to each other.

The best way to bed brakes in is NOT by slamming them on, but rather by applying firm, even pressure to the brakes which will help ensure they bed in correctly. Too light pressure and you could "glaze" the pad - i.e. turn it too hard and polished to effectively brake, too hard and you could damage the rotor or pad by scoring its surface or worse.

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    Does this also apply to rim brakes, or just disc brakes?
    – Goodbye Stack Exchange
    Commented Nov 25, 2010 at 16:03
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The how has been described already: repeated brakes to near stop from some speed to put heat into pads. Try to avoid holding the brake after you've come to a full stop to avoid uneven transfer of pad material.

I think the why hasn't been fully covered yet, aside from the fact bedding in transfers some pad material to the rotors/discs. But the reason this is important is that most of the stopping power comes from adhesion rather than friction. Brand new pads have only friction between hard pad and steel rotor. Friction alone - as you'll know if you've ridden on new pads - doesn't slow you very effectively.

Adhesive friction between the pads and rotor, particularly with sintered pads, is much more powerful. Imagine the pad sticking like glue to the pad material on the rotor. As the rotor passes through the pads it smears material from the pads, rather than grinding the rotor down.

Adhesive friction is also used in tyre technology, particularly for performance tyres. I have a picture from a recent track day where I was able to stick a screwdriver to the side of the tyre on my motorbike. The tyres were literally sticky to the touch when they hit their operating temperature.

The same thing happens to your brake pads when they hit operating temperature. So when bedding in you're just getting them hot enough to smear a coating on the rotor, ready for you to take advantage of adhesive friction the next time you get them to operating temperature.

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  • I think I follow, is the key point that it allows the pad to wear down, giving full stopping power, rather than the pad wearing down the disc, with lower stopping power?
    – Swifty
    Commented Oct 15, 2019 at 11:51
  • Seems reasonable. But would't that mean that what you should "Bed in" are new rotors instead? Suppose I replace my pads with the same exact type. The rotors are already coated, Should I break in the new pads?
    – Jahaziel
    Commented Oct 15, 2019 at 14:58
  • Yes, wearing the pad more than the disc is a side effect. The main point though is that the adhesive friction is much more effective than the abrasive friction.
    – Owen
    Commented Oct 18, 2019 at 16:16
  • Yes, new rotors with bedded in pads will be far worse than coated rotors with new pads. New pads of the same type as the old still need to be brought up to temperature a few times to get them going. Almost like they have a hard glaze from the factory that needs to go. New pads of a different type have both that process, and the need to leave their own pad material on the rotors. This is because they adhere better to their own material, than another that may have a different makeup.
    – Owen
    Commented Oct 18, 2019 at 16:19
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The reason for bedding them in is to get the proper performance and lifetime out of them that they were designed for. The process should be specified by the manufacturer. It will vary based on the pad's materials/design.

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Yes, you will need to do a series of brake applications to ensure a nice even coat of pad material is layered on the brake rotor or disk. What your essentially doing here is cooking your pad so that the rotor will have pad material transferred to it. Also, your also making sure the pad is mature enough to be used for those big hills. If you want to know what a rotor looks like when you do this wrong, then check this car website out: http://www.cquence.net/blog/brake_pads_and_install_guidelines/

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