What brakes are these ?

Austin318 · 10-22-2004, 11:04 AM

I saw this while going through the brake bleeding page and was curious to what rotors these are ?

http://www.pelicanparts.com/bmw/techarticles/Mult-Bleeding_Brakes/pic6.jpg

jonmatar · 10-22-2004, 07:53 PM

Those are high proformance "cross drilled" rotors..the holes help the rotor dissapate heat in high performace driving situations..less heat =more stoping power.

Austin318 · 10-23-2004, 10:13 AM

Sorry I should have been more specific. I have the cross drilled on my car I was actually referring to the color of the rotors.

jonmatar · 10-23-2004, 06:58 PM

oh lol sorry about that...i dont know about the color...maybe a costum job or something?

stupenal · 10-24-2004, 01:55 PM

Quote:

Originally posted by jonmatar
Those are high proformance "cross drilled" rotors..the holes help the rotor dissapate heat in high performace driving situations..less heat =more stoping power.

That is incorrect.

Here are the disadvantages and advantages of xdrilled rotors

Advantage
1. It looks cool, yo.

Disadvantage
1. most xdrilled are not cast with holes, the are drilled afterwards, decreasing the structural rigidty of the rotor. the holes often lead to cracks in the rotor, making it very unsafe (especially at the track)
2. it does not dissapate more heat. in fact, it dissapates LESS. What dissapates heat is mass. Bigger brakes, better stopping power. The holes decrease mass and thus, decrease braking power.

Many people ask - if porsche and mercedes use it on their stock cars, it must have a advantageous purpose right? Yes, it does but these rotors are cast with holes which is MUCH different from the "xdrilled bling" you find online.

jonmatar · 10-24-2004, 04:19 PM

Ok if thats the case what ARE the advantages of "casted" cross drilled rotors?

kocio67 · 10-24-2004, 04:45 PM

During hard braking there is a lot of gases between rotor and pads and cross drilled rotors should help to escape this gas more quickly alowing efective braking.

jonmatar · 10-24-2004, 04:49 PM

so wouldent any kind of crossed drilled rotor let the gas escape?..dosent seem that the casting would effect this at all.

kocio67 · 10-24-2004, 05:05 PM

Drilled rotors are just known for warp problem

stupenal · 10-25-2004, 02:57 AM

Quote:

Originally posted by jonmatar
so wouldent any kind of crossed drilled rotor let the gas escape?..dosent seem that the casting would effect this at all.

unfortunately it does. i've seen many pictures of xdrilled rotors that have cracked. And if you look at the cracks, they originate directly from one of the holes that have been drilled. While most people experience cracking from tracking their car, it doesn't mean that it cant crack under street use.

Even if the holes are cast during the manufacturing process, it still does not guarantee the brakes will not crack. I would assume the natural laws remain true - a solid piece is stronger than one with holes in it.

Stoptech also points out how xdrilled is merely bling

http://www.stoptech.com/faq/data/faq15.html

Here's a pic of the xdrilled off the mercedes S class

Jared at Pelican Parts · 10-25-2004, 07:23 AM

I have used cross-drilled in the past. You know what I found out? You get brake fade during canyon driving, they warp and also crack. I got some good solid ventil;ated rotors, and problems went away.

Austin318 · 10-25-2004, 09:51 AM

I got xdrilled since they looked cool behind my BBS RK rims plus I figured it would be like sand paper the holes would dig more into the pads. I only autox and street my car have had the brakes for almost a year and no cracks or warping yet. The brand is Zimmerman.

Next is E46 330 front and e46 328 rear.

I was just curious what the color of the rotors where if they had any special propertys to the metal.