Yep, you can constantly bed those brakes, they will work for a day, then you will get deposits and they will squeal again. They will never work right when cold and those driled rotors will finally wrap in 5k miles. Been there done that.

It's all for show. If you want good street performance go OEM. Not OE, but OEM for smaller price will be just fine

my first set of gross drill rotors last me 100k miles without any problem.

You put 100k on one set of rotors? :wow:

When I got my X a year ago, the rotors were shot and the brake pad lining warning was lit. I immediately purchased Brembo cross-drilled rotors in combination with Akebono pads. 12k miles later and I've never heard so much as a peep out of them. I never asked my mechanic if he bedded them though.

I also purchased both front and rear Brembo cross-drilled rotors. I used oem pads in front and Axxis in rear. No real issues, except when the vehicle sits for a while, a little surface rust around the holes. This cleans up as soon as I drive and apply the brakes, just like any other rotors. I did have an issue with the bmw pads. The one pad started to loose some surface, which caused the rotor to have a ring where the pad didn't touch. The brakes are more worn in now, and that issue is resolved as well. I don't know if the pads were old or something, but I won't purchase them again. Somewhere on x5world, I have posted pictures.

If anyone here is a brake expert please fill me in. I don't really get what the benefit of having cross-drilled rotors on street car is. From what I know, the larger mass of say plain rotors, helps dissipates heat heat better than cross drilled rotors as drilled rotors by nature have more metal removed from the rotor surface when the holes are created. So besides looks, what is advantageous about cross drilled on a street car?

From what I have read, slotted rotors seem to be better than drilled. They have all the advantages of cross drilled, letting built-up gasses and water escape, but they leave more metal for dissapating heat and slotted rotors do not seem to form as many cracks over time like the drilled rotors are notorious for.

You will get lots of opinions, but here is mine:

Cross-drilled are purely for looks on the street. That is a plus for many people. Others see them as looking like boy-racer mods. They also help with water dissipation, but that isn't much of a problem these days, with modern pad compositions, and BMW's pad drying functionality in the new models.

The negatives are that they have less thermal mass, and therefore lower performance (from a heat-dissipation standpoint). The increased surface area only matters in a steady-state condition, it is the thermal mass that is more important by providing more stops before the brakes fade. They are structurally weaker, but if well designed (ie designed to be drilled) that can be compensated for. If regular rotors are just drilled, they are more likely to crack. They are noisier by design, but chamfers can help there.

You mention outgassing, but that is not something you will find on street pads. Some people claim that they improve ventilation, but that is a function of the internal fins in the rotor, not the holes.

There are too many fake cross drilled rotors out there. Plain solid rotors are drilled for the looks and sold as the real deal. I would only buy a reputable brand and from a reputable dealer.

Thanks! :thumbup:

If you look at any of the high performance, high end vehicles, they all have crossdrilled rotors, including BMW. There must be a reason for that, not just looks. From what I have read, the holes do help cool down the brakes and rotors. I don't do any high speed racing/braking in my x. I purchased them because I had intended on towing a trailer, and I figured the better braking would be a plus. But we all know the trailer hitch story. I'm still waiting to find out how the brakes will work with the heavier load.