Poodles;1727167 said:
Crossdrilled was originally done on racecars to allow the gasses to escape. Brake pad technology is far better these days, and it isn't an issue anymore. They crossdrill rotors on "high end" cars because of the perceived improvement in the consumer's eyes (i.e. company will do what the customer wants). Also of note, most high end cars that come with crossdrilled rotors are designed for them. They're not normal rotors that are just drilled (as every single stock replacement rotor for our cars is). Most high end cars have brakes that cost more than the average MKIII as well (and the owners can afford to replace them)
Slotted covers the same ground, but doesn't have the "cut along dotted line" aspect of crossdrilled. Either way, the stop brake setup doesn't have enough mass to deal with the heat, causing transfer of that heat into the brake fluid. Brake fluid boils, causing fade.
Also, drilled and slotted rotors are 100% ricer garbage and don't belong on a real performance car. You do one or the other, not both.
Modern racecars either have neither (as is the case with F1 cars) or slotted (WRC for example, but usually they're an odd slotted). Can't think of any current serious race application that favors crossdrilled.
you have still alot to learn
about brakes
i going to go into very basic and lightly
first off
slotted rotor's (ie not power slot) are use for racing, metallic pads to bring the heat up in the pad so there brakes can work at there proper temperature, metlice pads don't gas as bad as semi or organic pad ie asbestos ect
another part that slotted rotors play is to cut into the pad for a good first bite
now lets say you run power slot and semi metallic pad......and lets say a heat rating of f/f you most likely end up glazing the pad from the heat that will build up from the slots in the rotor since they dig in on every revolution
from the pad gassing then melting and bringing the resin from with in deep in the pad thus destroying the pad and not allowing the pad to cool since not it;s heat transfer has decreased from the glaze that has formed
in the end power slot are shit don't run them and if you do get a poper pad for them (i must say they do work pretty good in the rain since there is slot for gassing from water vapor)
Drilled i pretty much as explained before
they bite quicker
they dispate heat faster
work very very well in the rain
harder to glaze the pad
great for semi metallic pad witch are great for street use because of ware mix with performance it get's (not to hot not to cold)
now to answer this cracking thing cracking comes form thermo shock from being cooled to fast water puddles snow what ever this can happen to any rotor but could be amped up if you using a drilled rotor
now lest say you have a good rotors spun casted in stead(good) of poored cast iron (not as good) and a good mix of carbon and all that other crap that goes into cast iron
these will hold up longer if they were liqued cooled drilled and put in the oven to re heat treat the rotor witch reduseing cracking and takes away the stress crack's ect
now your cheep drilled units are just blanks that are re drilled and then shipped out crappy and will fail ie power stop shit ass rotors (they had a bad wrap for some time not sure what there like now ) and china rotors
now as ian state if you have shit rotor and drill hole in it the rotor might have good chance to crack and from heat , hard spots
then loose it parallelism ( ie thin spots from the rotor having to much heat and haven to much run out wail heated
ie napa brand /lord co/ pep boy /ect
blank rotor's
well they can store more heat then slot and drilled they have the longest life and they can suffer from rain from water vapor
that about somes it up
( there is bmw out there maybe benz don't remember what one but the rain secore on the dash will trigger the absunit to pulsate the calipers to prevent water vapor keeping the rotor hot eghough so it will stay dry)
oh yae drilled and slotted rotors are for show there really use for them in less your crazy about unspung waight might as well run an aluminum rotor or move them in word beside the diff
well i think i explained about as much i chould with my lame ass grammer and spelling skills
gm's low drag caliper were shitty in the rain since they did not wipe the rotor down at all and had shitty performance in the rain since the pad did not drag as much as reg pad a rotor and did not wipe teh rotor down so they used organice pads
so answer to gm to fight this was directionale brake pads