[Old school]

I have been lurking around these boards recently and am experiencing the same brake dust buildup on my rear wheels as a number of you are.

No firm answer to why this is happening has been put forward but I believe I have found it.

I used to ice-race in my old VW diesel and use left foot braking to induce oversteer. This means applying the brakes at the same time as applying the gas so that you lock up the rears while using the engine to overpower the front brakes and keep forward momentum. This is one of the reasons why I bought a base-model non-ABS/EBD Mazda 3 because this driving technique does not work on ABS-equipped cars.

Usually when left-foot braking the engine will bog slightly before you get the correct amount of throttle dialed in to overpower the front brakes. I attempted a left-foot braking manoeuvre this morning and was caught off-guard when the rears locked up immediately at only the slightest application of the brakes. The engine did not bog either.

This means that the rear pads are either closer to the discs than the front pads, making them bite first, or the braking system is improperly calibrated and is sending too much pressure to the rear. In everyday light traffic you generally don't use much pressure on the brake pedal, which means that your rear brakes are doing almost all the work during your daily driving!

I am writing this at work and intend to go to the dealer as soon as I finish.

 

[rpc180]

I had a similar theory, wthe rear brakes being calibrated to teh point where they may actually be touching the rear rotors (I guess you could call it drag). Excessive amounts of dust would probably build up as well as excessive pad wear. A few guys here have found about 20% of brake pads worn away in just a few hundred miles. I guess if the rear pads are always in constant contact with the rotors it would also create grooving.

BTW, I think I'd have to see how you do your braking technique, it sounds fun but I can't understand how you do it from just reading

 

[Kermit798]

My g/f and I have been noticing the same issues with brake dust although I wasn't sure if the quantities were normal, this is my first experience with 4w discs. Anyways, we've noticed that the brakes are extremely easy to enguage with only the slightest touch of the pedal causing sometimes jerky braking. Is this abnormal with ABS in mazda's, or perhaps a symptom of calipers set too close to the disc?

I haven't checked the wear on the brakes today b/c of the 3 feet of snow the car is currently buried in, but will check asap.

 

[Old school]

BTW, I think I'd have to see how you do your braking technique, it sounds fun but I can't understand how you do it from just reading

It's a rally driving technique. You apply light pressure on the brakes with your left foot while keeping the throttle open with your other foot. This creates drag on the rear wheels, transfers weight to the front of the car, and allows it to rotate on its inside front tire axis. You can achieve pretty much the same effect with the handbrake but this way is quicker and leaves both your hands free to steer.

I don't think it would work on your car because it has ABS. Use a beater or rent a car without ABS and practice it in a snow-filled parking lot. You'll most likely stall it a bunch of times before you get used to applying light pressure with your left foot.

 

[mnemonicj]

I would think that having the rear brakes clamp first would be desired since it would create drag on the vehicle while still being able to steer with the front wheels. After the brake pedal is depressed so far then the fronts clamp too to stop the car completely.

 

[Old school]

I would think that having the rear brakes clamp first would be desired since it would create drag on the vehicle while still being able to steer with the front wheels. After the brake pedal is depressed so far then the fronts clamp too to stop the car completely.

Not quite. Braking force applied only to the rear wheels will destabilize the car. As I sort of explained earlier, putting drag on the rear wheels transfers the weight of the car forwards, making the tail end lighter and reducing traction on the rear tires, making it easier for them to lock up. If you try to steer at this point you will break the rear end loose and start spinning.

To try this out, go to a snowy parking lot, drive in a straight line at abou 15mph. Try to slow down using just the hand brake and then try to steer. Your rear wheels will lock up and step out of line.

That's why left foot braking does not work on ABS cars because the rears never lock up so you can't initiate a slide.

 

[DJ Spencer]

Speaking of ABS brakes - and I know I got an answer somewhere before - but when the ABS kicks in, is it supposed to sound like someone rear ending you?

This is my third car with ABS - and when I slam on the brakes because of some idiot pulling in front of me, the whole car shutters and jerks, to the point in which it sounds like I make have forgot to hit the clutch, or someone hit the back of my car (neither is the case).

It's just a very loud, quickly repeated THUD sound.

 

[Old school]

It's just a very loud, quickly repeated THUD sound.

That's normal. I personally hate ABS because I live driving on snow and gravel where it can be very dangerous.

Well, I get off work in 1/2 hour. Gonna go to the Mazda dealership and see if my theory's correct.

 

[DJ Spencer]

THEORY!!! THEORY!!! THEORY!!

Win one for the Mazda Forums!!

 

[mnemonicj]

I think that ABS sounds, and feels, like disc brakes that need to be replaced. If you have ever driven with rotors that need replacing you know what I mean.