Loud Brake

Oh_Seven

Member
:
Mazda5
When in reverse (and ONLY in reverse) the 5 will make a LOUD noise when backing up. For example, backing the 5 out of the garage in the morning, then hitting the brakes to ease onto the road ... EERERRRRRRGGGGG (that's the best example of the noise I can 'write'). It's not your typical squeeky brakes noise ... and only seems to be coming from the rear. It doesn't happen all the time, so it's hard to document it on video and stuff. Took it into Mazda, and nothing was detected.

Was wondering if any of you have had a similar problem?
 
That is you removing that layer of rust that occurs on the rotors when parked overnight.

If you modulate the pedal just right, you can make the most horrific sounds. But remember this is only while in reverse.

Here is an explanation I wrote in a previous post:

Yes, the problem is from oxidized material on the rotor surfaces. It is normal, and is common with newer vehicles which use metallic brake pads, and rotors.
High humidity speeds up the process too.

I have noticed it on several of my cars, and can say that it will be louder when backing up then when going forward. Therefore my theory is two parts.

1. Since we apply the brakes while going forward 99% of the time while driving the vehicle, the brake pad surface will be fatter at the trailing edge of the pad and thinner at the leading edge of the brake pad. This process is normal, and is just a physical effect from the direction of motion of the rotor, and the leverege of the brake pad in the caliper assembly when brakes are used.

2. The buildup of oxidation on the rotors, will be scraped off without much noise when going forward, but when going backwards, (i.e. backing out of a garage) this uneven brake pad surface is now going to be wedging the opposite direction in the caliper assembly creating a poor contact between the brake rotor and the brake pad surface.

This larger than normal clearance in the rotor to brake pad contact will trap the rotor rust under the brake pad surface, (instead of being scrubbed off if you were going forward). The trapped rust will vibrate against the rotor, and cause the squeal/groan. The problem is further enhanced because when we are backing up, we tend to apply the brake pedal softer.

Does this make any sense? Hard to explain without a diagram, props, and my little pointing stick!

 
Que?

http://www.youtube.com/watch?v=O9fpwj2ZQSM

Yeah, I've heard something before, but very rare. As mazdadude explains...

You should be OK...


Great youtube video, that replicates the noise I also will hear on occasion, although I never thought it was that loud outside of the car.(boom05)

I have never tried it, but next time I start to hear the noise while backing up, I will apply the E-brake in addition, and see if it changes the noise.
 
Last edited:
coolmazda5, that video is the noise to a T!!!! Exact same ... and yes, it sure as heck is loud ... especially in the morning when coming out of a garage - the echo can wake the whole neighbourhood up! haha

mazdadude, thanks for the write up ... that DOES make sense! I didn't think of it that way since it never makes the noise going forward.

Thanks a lot everyone! Glad I'm not the only one ... and even more glad it's nothing serious!
 
Ahh.. the groan (aka secret Mazda5 whale call). We only see it rarely due to out low relative humidity most of the time. That same surface rust gets between the hubs and wheels. Just put on the snow rims and 3 of 4 wheels were practically welded to the hubs for a little surface rust.
 
Back