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Discussion Starter · #1 ·
I am not sure where this should go since there is not a forum category for brakes, so here goes...

I am bothered by sudden brake grab in my CX3 GT. When starting off. When I just apply the brakes very lightly they will grab as though I stomped the brake pedal in panic mode. The first few times that this happened I almost had to manually push my eyeballs back into my head! If I wasn't wearing my seatbelt someone would have to scrape me off the inside of the windshield. (No quite but almost)

It is that way for the first Km or two and it really bugs me.

So I am wondering if anyone else is experiencing this. And if so, have they found a solution to the problem?
 

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Anchorman comes from 17 years in brake testing and development so this is right up my street.

How cold are we talking about?

Did this come all at once or was it a gradual development?

I don't know how familiar you guys are with small diesels but because they have no manifold vacuum they have to have a vacuum pump or exhauster to create vacuum for the brakes. Gasoline engines do not normally need a pump as the Pistons create high vacuum in the manifold so there is no problem keeping the brake servo charged - except........

........the Skyactive engines are different. They operate on the Miller cycle and at the unusually high compression ratio of 14:1. They are also fitted with a vacuum pump so I don't know at this stage if we are looking at a friction material issue or something on the actuation side like over servo assistance.

Can one of you guys with an effected vehicle pm me with a VIN No and I will see if I can pick up whether you are using the same friction material as in Europe. Some friction materials can absorb moisture which can make them grab when cold. This is particularly so after they have become conditioned by temperature as the surface becomes more porous.
 

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Discussion Starter · #5 ·
Actually I noticed this behaviour right from the start back in the warm days of November when I took delivery, so it is not just on very cold days. I thought at the time that this was probably something that would fade as the car got broken in with daily use, but it has not faded away at all. My car is not Diesel (we don't get the diesel in Canada). The VIN number is: JM1DKBD70G0115223.
 

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Could be due to a thin "film" of rust that has formed on the rotors? If the brake feeling goes back to normal after using the brakes a few times, this might be the cause.
 

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Same thing happens to me. It has been cold every since I took delivery so I cannot say how it performs in warm weather. But for the first few times from a cold start I use the brakes they're very harsh and grab quickly.
 

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Mine are very smooth and progressive which makes me wonder about friction material. I will check the parts list tomorrow.

If Gus looks in, can you comment on your UK gasoline engined Cx-3?
 

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I have never experienced any issues like mentioned in this post.

Temperatures here in Denmark has not been below -5 c since i got the car.
 

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Discussion Starter · #10 ·
Thanks, folks. I have a partial solution to the problem. Now after I start the engine but before I put the car in gear I push hard on the brake pedal a few times. Then when I drive off, the brakes still grab, but not nearly as much or as hard as before. So if it is a layer of rust that is the problem it should loosen up and wear off more quickly. I'll report back on how this is progressing.
 

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I have noticed this on my GT as well, sporadically.

It nearly feels like the brake lags for a split second, then suddenly it "registers" that I have stepped on the brakes and is like WOOPS LEMME BRAKE FOR YOU.
 

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No issues here. I've driven this car down to -26 degree centigrade and the brakes feel the same as any other temperature.

The only thing I can think of that may cause this issue is if you live in a humid or wet environment that causes surface rust buildup on the rotors. The pads will grab harder initially because of the rust. This has happened to me on my mazda 3 but not the cx-3.
 
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