advantages of dimpled rotors?

[Sowndwayv]

posted this question in the group buy post for the brembo rotors, guess it was the wrong place to ask a question.

"so if the dimpled ones arent drilled thru, then they wont release the heat? so what advantage does the dimpled rotors have over whole solid ones?"

[pinoyesv6]

they won't release the heat. they aren't drilled thru so u still maintain some of the structural integrety of the blank. they also look crossed drilled. o yea, the dimple helps give a lil bit of bit too just like the cross drilled

[Sowndwayv]

did u mean bit of gas?..anyways

i seen a pic of the crossed drilled rotors in the group buy thread? does anyone have an example of what dimpled rotors look like?

[pinoyesv6]

i mean a lil bit of bite...

[mochanges]

Tirerack has the dimpled rotors made by EBC, you can see them there. Most cross drilled rotors are justified by the vendor in several ways. One is weight savings. This one is hard to argue with, as a hole with nothing but air definitely weighs less than it would if it were filled with material. What some people wonder about is whether the structural integrity of the rotor is compromised by the holes. Porsche gets around this problem by not drilling but actually molding the holes when the rotors are made. Some say that any holes reduce the strength of the rotors and some also say they are bad for another reason: heat dissapation. See, most people think the reason you upgrade to bigger brakes is to get a larger diameter that lets the rotors work better, kinda of like a longer handle on a hammer so you can swing it harder. This is not true. The reason to go with big rotors is that a bigger rotors and/or caliper can handle more heat without fading. So, it seems that it would make sense that if you take a solid rotor versus a drilled rotor, the solid one will hold more heat just because there is more material. This is debated alot and the reduction in "heatability" may be offset by the cooling provided by the holes or the weight savings.

Another misunderstood idea in regards to braking is that of outgassing. Outgassing used to occur when pads were heated up and if you can imagine, gasses released from the pad would cause the pad to kind of "hydroplane" above the rotor surface, thus reducing the effectiveness of braking. The reason this no longer occurs is that most modern pads simply do not outgas, so there is no hydroplaning (If you use any organic pad, it may still outgas, but most performance pads have no organic substance in them). Stopping this hydroplaning has been the justification for slotting/drilling/dimpling rotors. Some also say that the slots/holes/dimples in rotors clean the pad surface. Again, this is also widely debated.

In the end, none of these questions are conclusively answered, and various manufacturers and vendors disagree with each other. I think the best bet is to go with what you can afford and what looks good to you. If you end up circuit racing, you will find out what works well for you pretty quickly, as you will put these various designs to the test.

-Mohammad

[Wintergalant]

That was well said mochanges!!

[mochanges]

Thanks.

-Mohammad