I've always heard from brake engineers that you should use slotted on a high performance (racing), 4WD, or towing vehicle, not drilled. Drilled looks cool, but isn't as strong as slotted. Hell, when I was racing, we were even using cryogenically treated rotors to get an edge. (And yes, in our testing, it actually worked... it was just stupidly expensive).
I might do some towing or mudding, but that's it. I guess my question is more: Is there any downside in daily driving with cross drilled? I've decided that instead of getting a new truck, it's probably in the best interest of my pocketbook to fix the few little thing wrong with my truck rather than deal with full coverage insurance & payments.
In the end, cross-drilled will blow up before slotted under stress, as there's less material, and what is left has holes in it that won't deal with extreme expansion due to heat as well as slotted does.
I don't know vehicles to the extent nett and some of the others do, but I know enough about metal from welding and some basic forging over the years. Each one of those holes in a drilled rotor is creating a failure point. On a drilled break rotor, you're placing a hell of a lot of failure points into the last piece of equipment you want to fail. I'm sure on a light vehicle you use for your regular commute, there wouldn't be many opportunities for failure so you'd be safe going with them for looks. But wouldn't trust them on an SUV or truck, never mind an AWD, and I especially wouldn't trust them if you're carrying or hauling anything heavy (other than that chick you picked up at the bar). You're talking several dozen points of failure -- thanks to the stresses between and around the holes and tensile strength of the material) Slotted, at least from my understanding, works more like a fuller on a knife. Little lighter, more surface area, basically the same structural integrity as blank rotors, and I'm guessing a little better bite due to more friction between the rotor and pads... speaking of that, if you're getting new rotors, make sure you check out your pads too, replace if necessary and upgrade if possible. Otherwise it's like doing a body lift instead of frame and thinking you can go rock crawling now.
The holes vs slots isn't about surface area... it's about material integrity. Drilled generally get cracks around the holes with any kind of use, until they get big enough that they're considered dangerous. I've had to give a thumbs down on more than a few cars in their tech inspections due to the drilled rotors having 1/4" cracks off of the holes, but I've never seen that problem with slotted rotors. (We used to take turns helping do IMSA tech inspections at our local races). The slots maintain the integrity of the rotor much better, while still allowing the channels for the brake gasses that are generated by heavy braking to escape and not create a boundary between the pad and the rotor that will lessen the friction/braking forces.
The 2nd hole is a bit of an extreme example of failure, but if you take a look at the 3rd hole, that is pretty typical and will spread with continued use. Some of the cheaper, "cooler" looking rotors become quite deadly fairly quickly:
If you Google image search for "slotted brake rotor cracking" you'll be hard pressed to find any, because they don't really cause any cracks... if the rotor is going to go (in a slotted rotor), it's generally the whole thing that will go, nothing to do with the slot. To cover all the bases, some rotor companies started making both slotted and drilled rotors, espousing the best of both worlds, but we still found that the holes cracked and didn't provide any additional braking power. FYI, we spent one full 24 Hours of Daytona (about 6 weeks of track time) as a guinea pig for Hawk Brakes... testing their latest racing brake pads and floating rotors... we tried about 10 different combinations of pads and rotors of all kinds, and ended up picking slotted. Yeah, if you want to be REALLY bad ass, put some floating rotors on your truck. Best. Brakes. Ever. Just a bit loud.
And just in case anyone hasn't heard of "floating rotors", here's a pretty good video I just found that explains it.
Ok. Y'all have convinced me. I kind of had my doubts about cross drilled, simply because of what RoTN said...they seem to set up weak/failure points. That's why I never used them on my 300ZX's...they seemed like something that would probably be bad under extreme stress. Apparently they're probably a bad idea under normal stresses too.
Most performance street motorcycles have had slotted floating disk brakes on them for years. They are amazing for the feel they give you as you are braking.
What is 35 feet long, has a V12 diesel and two 6-71 blowers? This thing. I don't know what I'd do with it, but I want it.
Toytoy, I wouldn't pay a dime for cross-drilled rotors. Or even slotted ones. And I work with brakes every day. Just get some good quality conventional rotors (not a cheap parts-store brand), and you'll be fine. In other news, Snap-On was having a sale on striking pry-bar sets, so SCORE FOR ME!
The mystery of my truck continues. Today I had a mechanic run diagnostics on my truck. I was sure I had a faulty TPS behind the hard starting and occasional idle hunting. It didn't throw any codes. It said the TPS was functioning correctly and that the CEL wasn't lit up (It was.) The mechanic had no idea what the hell the issue might be. It's something in the fuel delivery, I'm sure of that, but beyond that I have no idea if it isn't the TPS. The idle air has been replaced (Twice), the computer is new, the whole fuel injection system has been replaced and it still acts wonky. Cold starts it has to crank for 5-8 seconds before it hits, warm starts after it's been sitting 20 minutes or so it acts like the engine's loaded up and then hunts for idle, either reving itself or just giving up and dying. The mechanic did ask me a question I've wondered about...."Does it have a cam?" I honestly don't know. It does lope like it's been cammed up. It also has a K&N CAI, no cat, and the exhaust dumps straight from the manifolds into a couple of mufflers. So it has certainly been modified. Anyone have any idea which direction I should chase after now that the TPS isn't the culprit?
It doesn't. Did it have one stock? I have no idea. The CAI goes directly from the K&N cone into the fuel injection.
That could be the problem then... I'd check the manuals for whatever make/model/year your truck is and see if it has a MAF stock. That's what tells the ECU how much air flow is going into the engine, and adjusts fuel richness/etc based on it. It's a key data point for fuel injection. If they fucked up the CAI installation and pulled out or damaged the MAF, then your ECU is running blind, and can cause things like really rough idles, as well as it running too rich or too lean.
No, Dodge stubbornly refuses to step into the 21st century and ditch speed-density engine management. Toytoy, I'd check and make sure that your EGR valve isn't sticking open. A truck at work (also a Dodge) was kicking my ass for awhile (it was idling like shit, WHEN it would idle), and that turned out to be it. Also, make sure that the EVAP purge solenoid isn't stuck open, either.
Got this two weeks ago tomorrow. No, it's not a Malibu. 415 horsepower, 415 pound-feet of torque motherfuckers...