CROSS DRILLED ROTORS

Q: I understand crossdrilled rotors offer substantial benefits in cooling, but they crack and fail almost immediately, how can both be true.

A: Actually neither is true.

There are really only two reasons that rotors are crossdrilled;

1) To relieve the gasses emitted from the breakdown of the bonding agents used in the manufacture of some brake pads. This condition, known as "outgassing", can create a pneumatic barrier between pad and rotor which results in a ormal pedal feel but very little friction to stop the ehicle. Ironically, current race pads from Performance Friction and several others are pre-burnished and do not have any outgassing problem;

2) For COSMETIC reasons. The truth is today's ever larger and increasingly open wheel styles, the brake system has become instrumental in creating a "look". Porsche and Ferrari, as an example, certainly know the need for crossdrilled rotors has passed, yet they still deliver their top of the line cars with crossdrilled rotors. This is the same reason that Baer offers all systems with or without crossdrilled rotors.

Crossdrilled rotors do offer about 15% less service (life) in most serious to extreme street use. In actual track use this reduction can be upwards of 50%. However, most SPEs (Self Proclaimed Engineers) suffer from the mistaken conclusion that the small hairline fractures which migrate from gas relief holes indicate "a rotor which is terminal and must be replaced". This too is untrue. these surface fractures are normal with any crossdrilled, slotted, or "dimpled" rotor. the cracks which warrant rotor replacement are any which actually cause a pulsation in the pedal, or which are radial thru the edge of the rotor.

So if you encounter claims that crossdrilled rotors will measurably increase performance, improve cooling, or last as long as non drilled units, talk to someone else.

In racing, crossdrilling was designed to alleviate a problem known as out-gassing. In some of the older pad compounds, when the pads reached elevated temperatures consistent with performance or racing use, the binder (that’s the material that holds the friction material in place) boiled off, producing a gas. This gas would build up between the rotor and the brake pad, effectively keeping the pad from directly contacting the rotor. The holes provide a relief path for these gasses, as do slots, so the pad can once again contact the rotor. Crossdrilling was NOT designed to facilitate cooling.

Originally posted by Jeff92se
http://www.tubas.net/~drew/ner/brakebasics.htm

Originally posted by MichaelAE
I am primarily posting this here, since I posted it in a thread about a group deal on rotors that Dixit put together. I thought it would be of broader interest:

This is from a FAQ in the Baer Racing Catalog:



Another quote from their information:



Baer themselves, actually only sell cross-drilled rotors as a "cosmetic" upgrade. I'm just posting all this to put the debate between dimpled or cross-drilled aside and make this what this is...a cosmetic modification at a good price.

Originally posted by woreyah
Sounds good. I just want to know what will prevent brake fade during city driving. On a hot day like this (95+ degrees) it especially pronounced. Are they saying that most brake pads elliminate this? I had Performance Friction on my SHO and had the same problem.

Originally posted by MichaelAE

I'll be honest my man...I'm not a self-proclaimed engineer...I'm a real one but, unfortunately, of the Electrical variety so I'm not the guy to ask. I understand the basic physical concepts of braking, but am merely doing my research as far as the physical benefits of cross-drilling and slotting rotors. My feeling, based on what I've read is that increasing the rotor diameter would both increase braking power and decrease brake fade as the larger diameter would increase brake friction and the larger mass would increase cooling ability. These stock-sized replacements are, really, just a cosmetic upgrade as far as I can tell.

Now, the brake PADS and the brake LINES I find are recognized as excellent brake performance upgrades.

Originally posted by Max_5gen


Some simple physics:
IMHO, brake friction doesn't depend on rotor's diameter, at least directly. If your car is moving at certain speed and you bring it to complete stop it causes all car's kinetic energy dissipated on rotors no matter what type of setup you're using. Yes, with larger rotors (with bigger surface, not necessarily mass) they will go to less temperatures and pads won't probably fade as much. But as you've said you could upgrade pads and leave rotors alone - some aftermarkets can go really high in temperature without fading. BTW, we don't need to increase braking power since anybody could lock their wheels completely with stock setup. Lines give you better "feeling" but don't change anything performance - wise.

Mike.

Originally posted by Max_5gen


Lines give you better "feeling" but don't change anything performance - wise.

Mike.

Originally posted by Jeff92se
True but I think the Maxima is the largest Nissan to still use the smaller dia rotor and single piston calipers. For ONE panic stop from reasonable speeds, it's probably okay. But do the same from a 100mph and I think these brakes will start heat fading fairly quickly. Just IMHO, I think the maxima needs the rotors/calipers from the 300z or Q45 at least(size wise).

Originally posted by look2me40
There are a lot of companies and individuals that say that upgrading your brakes is a 'cosmetic' mod. From my OWN experience...I formed my OWN opinion on the upgrade to my brake system. That opinion would be that it definitely IMPROVED the stopping ability of my 2002 Maxima. The results could vary from car to car and I have no clue WHICH piece of equipment that new found stopping power could be attributed to. But to say that these upgrades are purely cosmetic? I just don't see it from my experience. I swapped out the calipers, the rotors, pads and brake lines. I have been told my calipers were 'cosmetic' upgrades and then I was told my rotors were 'cosmetic' upgrades... Yes, they look sharp. But on top of that, they do have some effect on the stopping abilities of my vehicle. Again, these are MY opinions and can be ignored as far as I am concerned...but I have seen numerous posts on the .org on how useless new rotors or brakes are performance wise and I think people should hear both sides of the story. Thanks.

Originally posted by look2me40
There are a lot of companies and individuals that say that upgrading your brakes is a 'cosmetic' mod.