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I recently bought a new car and it came it with disc brakes (specifically the Brembo's that come with the new BRZ). If the conditions are rainy or snowy out, I've noticed there's a significant amount of time (up to 2 seconds) from when I press the brake pedal to when the car actually starts slowing down. There's essentially no deceleration unless I slam the pedal down or give it a few seconds. This only seems to happen after a period of not braking (say I'm on the highway for 15 minutes). I've never had this happen on my previous vehicles (but they all had drum brakes) and the brakes work as expected in dry conditions.

Is it normal for disc brakes to lose functionality like this in wet conditions?

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    Welcome to Motor Vehicle Maintenance & Repair!
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Dec 5, 2018 at 20:05
  • In general, disc brakes, if wet, are much better at stopping than drum brakes, if wet. But you are comparing your current car to a previous one. Did the previous car NOT have anti-locks and the new one does so perhaps you are feeling that difference?
    – mike65535
    Commented Dec 5, 2018 at 21:57
  • @mike65535 Yes, I believe the new car has ABS but I’m not certain on the previous car (05 Civic). Would anti-locking system even trigger when braking normally? Could you explain how having ABS could make it feel like the brakes aren’t being applied?
    – Paul Warnick
    Commented Dec 6, 2018 at 3:26
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    An '05 Civic likely had ABS (it's been pretty standard since late 90s). I was suggesting that perhaps the ABS was backing off on slippery roads (You said "rainy and snowy". The common denominator being low road friction.) For certain, the driver "feel" of the ABS operation of one car can be VERY different than that of another car.
    – mike65535
    Commented Dec 6, 2018 at 13:40

3 Answers 3

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Sounds like your brake pads are dropping out of their temperature range.

OE brake pads are designed to handle extreme driving conditions, but driving at higher speeds in cold and wet weather will significantly reduce the brake system temperature, sometimes below the standard operating temperature of the brake pads. Since you're using an OE opposed piston caliper designed for higher performance, they will usually fit slightly higher performance brake pads in there as well.

If you search for 'brake pad friction profile' you can see graphs of temperature (x axis) vs pad mu (aka friction, y axis). These graphs will usually resemble a wide bell curve, where the pad as very little friction below a certain temperature, have stable friction within a temperature range, then the coefficient of friction will begin to drop off (aka fade) as you exceed that pads working temperature.

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  • That’s interesting, so would you say this isn’t as much of a problem on car without performance brakes? Also, I’ve only had the chance to drive the car during the winter, will the brakes likely stay within their temperature range in the summer, reducing the problem?
    – Paul Warnick
    Commented Dec 6, 2018 at 3:21
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    Yes and no, it wouldn't be as much of a problem on a car without performance pads, specifically. In the summer your rotors/pads will still cool way down during freeway driving, but obviously ambient temps will be higher so they won't cool down as much, meaning the time it takes for your pads to build up enough heat to work again will be much shorter.
    – MooseLucifer
    Commented Dec 6, 2018 at 17:02
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It all depends on the kind of brake pads and disks you have. You lose your brake power when don't use brakes for some period of time, because get wet and they need some time to get water off in order to brake.

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New brake disks and pads take a few hundred miles to bed in properly, and before that they can feel a bit spongy and need more pedal force.

If you still have this after say 500 miles, I would think there is something the dealer you bought the car from needs to look at.

Even on a "low specification" car with disk brakes, you definitely shouldn't be getting a 2-second delay before anything happens once they are bedded in.

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    Brakes do not take xxx miles to bed. You can (and should) properly bed your brakes within a few miles of installation. Brake pads/rotors and considered 'bed' once the brake pad has deposited a very thin, even layer of pad material onto the surface of the rotor. This is done by slowly bringing the pads and rotors up to a few hundred degrees (F) to create this layer, then evenly cooling the system back down to 'bed' the layer on to the rotor surface.
    – MooseLucifer
    Commented Dec 6, 2018 at 0:09

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