Warped rotors ??? Maybe not !

[Moose]

Ok ... I figured I would share something I have experienced with the OE brake on my 2006 Sport.

About 5-6 months ago I noticed intermitant shaking under braking (about 10K on the car at the time) ... one day it would be there, one day it would be fine ... it would be bad for a couple of weeks then it was fine again, ultimately it got progesssivly worse and was almost continuous.

In the spring I went to a road-race school with the 3 and I ran it pretty hard on the Track, the shaking under braking that was there on the drive up, went away and did not come back for a long time. But eventually it did come back. The Hard braking at the track appeared to fix the problem. Hmmmm a bit counter-intuative, you would think that abusing the brakes would make things worse.

Well it came to me in a flash ... the shaking under braking I initially attributed to warped/warping rotors could not be this, but it was something completely different, the pad material. The track abuse cleaned off the rotors of the old transfer layer and replaced it with a new good even layer.

Under braking a transfer-film layer of friction material (from the pads)is applied to the rotor surface. This allows the brake pad material to rub against itself rather than the bare rotor. This increases the stopping performance of the brake pad and can reduce pad and rotor wear.

Well apparently during city driving the OE material was NOT properly tranfering to the rotor ...it was doing so unevenly, causing the rotor to go out of square and balance ...causing the shaking.

To test this theory I changed the front OE pads for a set of aggressive street pads (Grandsport GS-5), I did NOT resurface the rotors ... just slapped the pads on, and went out and bedded them in properly.

Well beside the increase in braking performance the shake is totally gone and has been gone for months.

Soooo ... Before you replace you rotors because they are \\\\\\\"warped\\\\\\\" do some aggressive stops (in a safe mannor) and see if the shaking goes away or is minimised ... if it getts better then look at upgrading the pads, as your rotors may be fine (obviously inspect them ... if they are heavily rusted or worn, replace them)

Note:
The Bedding in process (a series of progessively higher speed stops with a long cool down period) allows a good and proper tranfer layer to be created on the rotor surface ...This is critical to proper brake performance. All high performance brake pad manufactures reccomend a specific bedding in process.



Cheers

Moose

[CoolColombian]

Thanks for the heads up, at todays meet we were actually talking about this shaking under braking thing and this is a good clue about its origin, maybe we all should put a lot of attention on this to give mazda the heads up on the pads they\'re using.

[3GFX]

Ok that explains a lot, and is very helpful. I had this problem while driving my mom\'s accord. After hard braking it too would go away. But in the end I did warp her rotors as they had to be replaced at only 55 000km. Guess I drove her car a little hard ;) Ahh to be 18 and powersliding into your highschool parking lot...the memories. :D

[MAZDA Kitten]

Is there any way to tell physically if you have a warped rotor? Besides taking it off but while its on the car

[Moose]

Originally posted by MAZDA Kitten


Is there any way to tell physically if you have a warped rotor? Besides taking it off but while its on the car


Yes, But you need a run-out guage.

Basically you need to put the car up on jackstands, remove the wheel, and lay the gauge against the rotor as you rotate it ... the shop manual will specifiy the range of allowable movement before machinnig is required.


Moose

[3GFX]

Basically what Moose said about a shimmy feeling when you brake is how you tell. You can feel it in the steering wheel. If it\'s bad you can see it too. Another way to tell is to see if you have burn spots in your rotor. Check if there is any \"blueing\" on your rotor. By blueing I mean that heat caused blue you see on metal.

Try doing what moose suggested above with hard braking. If that doesn\'t cure it, you probably have warped rotors.

[MAZDA Kitten]

I am pretty sure it is a warped rotor because a lot of members on here had the same symptons (as in hard braking from approx. 110 km/h to about 80 or 90 and the streering wheel vibrates pretty bad. Otherwise there is no problems any other time.

I\'m on the verge of buying new rotors anyways; the car has 70,xxx km and never had brakes changed.

[Moose]

Originally posted by MAZDA Kitten


I am pretty sure it is a warped rotor because a lot of members on here had the same symptons (as in hard braking from approx. 110 km/h to about 80 or 90 and the streering wheel vibrates pretty bad. Otherwise there is no problems any other time.

I\'m on the verge of buying new rotors anyways; the car has 70,xxx km and never had brakes changed.


This is exactely what my car was doing untill I changed pads ... It could be rotors ....but not nessessarily ...


Moose

[MajesticBlueNTO]

unless you do stupid things like:

* drive real hard till the brakes are smoking
* engage the e-brake while the rotors are hot
* and throw a bucket of cold water on the rotors

EDIT: in that order

you will not get a physically warped rotor.

even if you engage the e-brake on hot rotors, there still may be hope that re-bedding can alleviate the vibrating symptoms.


in any case, like i\'ve said in previous threads (i think i even explained the pad transfer like Moose did), if the steering wheel vibrates at high speeds when applying the brakes, RE-BED the pads first.

majority of the time a \"warped\" rotor can be \'cured\' by re-bedding.