Jim Will

I installed Zimmerman slotted rotors (from ECS tuning) last week. Installation was simple, (after I learned how to order the correct offset) and I took the car for a test drive to bed in the rotors to the pads. (pads are about 3 months old, Mintex Red Box)
Upon heavy braking, both while bedding them in, and now about 7 days later, I swear that I can feel the slight rumbling from the rotors, or should I say from the slots passing over the pad surface. It's definitely not my imagination. I installed the rotors with the slots away from the direction of travel (since there was no specific direction listed anywhere that I have seen) meaning that the slots sweep away from the front of the car when in motion. Is there a correct or incorrect direction of the slot? does anyone else experience this as well?

All Wheel Driver

it's possible the pads have caused the rotors to bed in strangely.
I always thought it wasn't a god idea to put on new rotors with used pads. At least without smoothing the pads to a like new surface.
If there are grooves or strange wear on the pads from the old rotors, you may end up transferring that to the new rotors.

I've used slotted rotors before with new pads, and I never had that happen.

I did have a problem once with drilled rotors and the pads not bedding in well. I tracked the car and the brakes developed a wicked vibration.
I had to have them turned to cure it.

I'd call ECS, explain what happened, they helped me with my problem stated above.

4Driver4

Might take then a while to wear in though.

TXurS6

We had a discussion about this several years ago but I can't find it. One rotor manufacturer recommended the slot orientation as '\' for the driver's side and '/' for the passenger side. I would have thought the opposite and there was no conclusion as to why they recommended that orientation.

I think the more important thing to consider is the cooling vent direction. I'd call ECS and ask them...

However, it could also be that your pads have not sufficiently worn down to match the rotor face yet.

Eric 2.7

when they're wet.

MarkW

My slotted are slightly noiser and have that slight rough feel too. All slotted I have had do this.

néné

I put the Zimmerman cross drilled, and a few months later I noticed a rumbling under hard braking. A few days later, now it seems to happen at all kinds of braking.
Both pads and rotors were new. This is the last set of this stuff I buy. Don't like having to deal with that kind of noise, and vibration of the pedal. Small, however noticeable.

Back to stock set once it requires re-doing it.
Seems like crappy material.

BernieBenz

serving no useful purpose excepting to relieve a fat wallet.

GPZ

Nope! There was a huge improvement in both of my cars that I went to either slotted or cross drilled rotors on over the stock rotors. Especially the slotted. It kept my pads from getting glazed and fading on both cars.

All of my motorcycle rotors are cross drilled, for very good reason.

You should have used new pads on the new rotors, or else ground the pads flat. New pads on old rotors = OK, New rotors and old pads is not OK. The direction of the sweep of the slot sounds right, but won't make a huge difference either way unless you are tracking your car.

Extra noise on braking is generally not a reall issue, as long as it isn't squeeling or screatching

néné

I've had a BBK upgrade with slotted from Brembo and this issue did not occur.

I have a BBK upgrade from Mov'it, with x-drilled rotors, and the issue is not there either.
Even my stock RS6 rotors and pads did not have this issue, and they are x-drilled.

I've only seen this issue with Zimmerman rotos and pads. I think BernieBenz might have mis-understood what everyone was trying to say, and generalized it, which is just plain wrong!

So, I'm with you on this one GPZ! BernieBenz needs extra sleep!