I meaured the front rotor thickness by the "lip" that's evedent along the edge... it showed ~1.5mm, so I'm assuming its the same on the rear, and resulting in a rotor thiskness decrease of approx. 3mm. Measurement was taken by a precision caliper.

ran OEM pads until they were down to ~10% fronts and ~25% rears. Replaced with EBC Red Stuff (with that break-in coating). Now, front pads are at about 15%, while rears are still at like 60%+

now, I've got a full set of NICE custom centrix rotors sitting at my office which are double xdrilled and slotted, so here are my questions:

1. why would OEM pads wear down at roughly the same rate, while my red stuffs wear so much faster in front than rear??

2. I need to replace front rotors, and since I have a full set of rotors, I want to replace all 4, but I don't really want to change the rear pads since I don't want to spend an extra $100 on rear pads. Can I change just the rotors on the rear and leave the pad as-is? or will this mess up the rotors faster?

3. Seems like the STi brakes are a bit front-biased, so maybe I can leave the EBC reds on the rear, and get a less aggressive (and rotor friendly) pad in the front?

4. I've heard that slots should sweep forward, but I've also read the opposite, with the slots made to sweep debris away from the pad's surface, with the centrifigal force, but running the slots facing forward would do the oposite?

slot (/) rotation (->) / -> or \ -> ????

5. Anyone have experience with Centrix rotors before?

-Thanks!!

 

If you track (road course) your car, avoid using drilled rotors - slotted will work for any intended use. Manufacturer usually includes instructions for rotor orientation. I used DBA slotted rotors and they came with instructions. It isn't just the slots that determine directional orientaton but also the vane design in ventilated rotors.

I don't know why your replacement front pads wore out so much faster than the OEM but it's normal for the fronts to wear faster because of the front bias. Aggressive driving and hard braking might wear the fronts faster since they do most of the work because of weight transfer.

--
0==WW==0
"…axles of evil…" - george w. bush

 

I replaced my stock pads at about 18k miles, and the car now has clost to 38k miles on it. the stock pads did see 2 track days at streets of willow though, and I slapped on the pads to the old rotors without any resurfacing. the EBCs did have a"pad brek-in" coating though. no noise at all, and good performance....

As for the x-drilled rotors, I worked with the shop that CNC'd the disc, and we've made sure that the holes didn't drill through any vanes at all, and the CAD software we used to design the x-drill/slot combination was able to apply heat to the rotors based on pad size, friction co-efficient, ambient air temp, airflow, and rotor construction into the simulation, and the x-drilled hole indeed do help cool the rotor to a good degree.

despite what everyone says about x-drilled rotors, I would rather trust the CAD simulations and BMW club racers on the topic.

besides, I only do some light track, so I doubt I would have a problem with stress cracks. especially running just a high performance street pad.

-

So... is it okay to swap rotors while using the same old pad in the rear???

 

Before you get the wrong impression of "cross-drilled" rotors you should not that there is a difference between cross drilled and casted with holes (I'm sure there is a more technical term but thats the best I can come up with for now).

You'll notice that Porsches and Ferraris will come with rotors that have holes in them. They are running Brembo setups with rotors that were casted with the holes in the rotors. Casted with holes are much stronger than "cross-drilled."

But DO NOT go out buying the Brembo sport rotors that have been "Cross-drilled." Even tho they are Brembos they are infact cross-drilled and not cast.

 

there's a bunch of theories out there.... chamfering the drilled holes reduce stress, drilled vs cast holes, etc etc etc... I'm not going to do any serious road racing, and STi rotors are massive anyways, so i'm not too worried. besides, I don't have super-sticky tires, so with all that in mind, the least of my worries is working the brakes to a point where heat would be a concern. worst-case is if they do crack, I'll just toss on some blanks or slotted centric rotors.