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Inconsistent brake response

7K views 14 replies 12 participants last post by  georose 
#1 ·
2014 Mazda 3S GT. Full Technology package.

The brake response on my car seems very inconsistent. Sometimes the slightest pressure applies the brakes extremely hard, while at others more pressure is required than with other modern cars (though nothing like my old Saab 96 with disk brakes and no power assist -- stopping that car was a workout in itself). The brakes themselves work well -- it's just the inconsistent pedal pressure that is bothering me.

Does anybody else see this?

I thought it might be the Smart City Brake Support feature, but turning it off doesn't seem to make any difference.
 
#2 ·
Are the driving conditions the same when you feel the differences? The brakes warming up or drying off can make a difference to the feel in the pedal. Brakes can often feel very 'grabby' when the discs/pads are damp (As opposed to wet, when they are worse).

For example, cold brakes on a cool damp morning may have grabbier brakes than on a dryer morning. The humidity in the air can make a difference. This wouldn't really affect warmed up brakes though.

If the conditions are the same when you feel this difference, then I would be worrying about the assist stuff. I hate computers having control of basic driving inputs :)
 
#4 ·
When the air is humid, the brakes will not be as responsive, well at least for me and all of the cars that I've had. Besides this - think about what speed you're going to apply the brakes.

When you tap the brake pedal going 75 on the highway, they grab really hard because of the heat involved. If you are trying to stop going 5mph, then you'll need to apply a little more force considering those discs are not really spinning.

Am I making sense or am I just insane?

PS - SAAB Brakes, I felt your pain...
 
#5 ·
I'm guessing this happens after you start up your car?
or when you are driving for a period of time?
the brakes are overly sensitive..i have the same issue only after washing the car down and hosing down the brakes.
 
#7 ·
I notice this too..nothing wrong I guess. It's probably the brake booster vacuum at work. I notice that this occurs mostly when I'm driving around parking lots or when I apply light pressure then repeat immidately with a little more pressure. The brake will over react with more force then my foot requested.
 
#10 ·
I have plenty of experience with this effect on many cars so I believe there is something to this idea. However, when you google for "wet brake reaction", there is only one hit that has those words in that order, in one sentence, and that single hit is this page, lol.

Are you sure it isn't called something else? I have tried looking for it, but so far only come up with a bunch of car owner forums where someone complains about grabby damp prakes :)

The most compelling theory I have seen so far is that in humid conditions, there is a lot more surface oxidation on the disc surface, so it creates a higher-friction junction, creating that 'grabby' feel until you wear it off.

Tom...
 
#12 ·
I have the same problem with my 2015 i touring. Pedal inconsistency, especially at low speeds in bumper to bumper traffic. Thought it was master cylinder. Car passed all vacuum tests. Dealer said car was normal. I am now convinced it is the ceramic brake pads which have lousy bite when cold. This is a common problem for ceramic pads. They need to heat up to be effective. Any time temp is 50 degrees or lower I have to pre-brake to warm them up, then they brake fine. They need to be hot to work right. I hate this and am looking to replace them ASAP. The problem is I can only find ceramic pads for my car. Trying to find metallic replacement pads, but no one seems to have them since car is so new. Maybe there is a ceramic brand that works better when cold than OEM. Any ideas?
 
#13 ·
I've noticed inconsistency with my brakes as well. I think the brakes are spongy/grabby when it is damp and cold out. I've only got them warmed up really well a time or two, when they seem to firm up and give a better response. But I only have 1000 miles on my car and winter tires, so I've not abused it much yet.
 
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