RX7s

is it worth to get the stock brake rotor up grade to cross drill or slot rotor and which one is better

Ef-Dee

Cross-drilled is more about SEXXXY looks, while the slotted is more durable than the drilled...

Cypher

I believe the slotted rotors helps in heat disapation, does the cross-drilled rotor have the same benefit over the stock rotors? Either one have an advantage on stopping??

Fritz Flynn

iTrader: (263)

Slotted good for rain and drilled good for cooling or reducing break fade.

Ef-Dee

But, drilled doesn't last as long because it's not as durbale since it has holes in them...Let's just say that if you're rich and you can replace cross-drilled anytime you want, then get em, otherwise, stick to slotted or stock

RX7s

do these rotor help stopping power??

ek9220ps

iTrader: (4)

I THINK THAT IT DEPEND ON YOUR PADS, IF U HAVE STOCK PADS ITS BEST TO GO W/ CROSS DRILL, AND IF U HAVE PADS THAT CAN HOLD MORE HEAT GO W/ THE SLOTTED. THE CROSS DRILL IS BETTER FOR COOLING NOT STOPING. THE SLOT HAVE MORE STOPING POWER.
IF U LOOK AT MOST OF THE RACE CARS LIKE RALLY, AUTO CROSS THEY HAVE SLOTTED ROTORS.

DeNguyen

the only thing thatll make you stop faster is better tires and weight reduction.


all those brake components will only help reduce brake fade and increase brake torque.

maxcooper

Drilled tend to crack if you track the car, but are fine for street driving, and look cool. I don't think they improve braking much because pad compounds these days don't outgas much.

Slotted are more durable, but I don't know how well they'd hold up to track use in the stock size. Slotted clean the pad surface, which can improve braking consistency.

Solid face. stock style rotors are best for the track because they resist cracking the best. They certainly don't look as cool, but I know when I see a car with drilled rotors that the driver doesn't take it to the track, which detracts from the "image" a bit.

-Max

BrianK

ding ding ding! Max wins (again). The only thing I'll add is that cross-drilled rotors that are cast with holes in them are thought to hold up better than solid faced rotors that are drilled to have the holes (i.e. Porsche rotors).

Drilled rotors where originally intended to help remove the pocket of air that would form as pads got really hot and started to "boil" - causing the air pocket between pad & rotor. They were, and still are, not inteded to reduce heat (contrary to popular belief) - even though that may be a small side effect because of the slight addition of surface area. The same goes for slotted.

rtryrktrx7

I bought these for my Suburban:
STAGE-II Thermo-cooled slotted rotors and disc pads are both cryogenically treated for maximum cooling and faster heat disipation, resulting in longer rotor & pad life and shorter stopping distances. These thermo-cooled rotors consist of a composite casting with 30,000 PSI, running as much as 40% cooler than stock rotors.

I was also told you can turn the slotted if they get warped. Cross Drilled you can't. You throw them away and replace them. If money is a factor you might want to go with slotted.

Here's a link to their site. Unfortunately they only make brakes for american vehicles, but it might help you if your interested in reading about slotted rotors.
http://www.praisedynobrake.com

I had drilled once, but I liked the slotted better.

Also for any of you who have a truck or SUV especially by GM, and the vibrating, warped, squealing brakes are driving you crazy...Get this kit. It got rid of all those problems, plus increased stopping. I used to turn my rotors about every three months because the brakes are under powered on these trucks, and they would warp and sqeal all the time.

DamonB

I need to post pics of a champcar front brake rotor I have from Fernandez's car last year. By rule, CART brakes must be iron (except carbon on superspeedways), so they have the state of the art in iron discs. First off it's HEAVY, it takes that much iron to dissipate the heat. It has wide cooling vanes in the center and it is slotted on both sides. NO holes. I think holes look sweet as hell too, but they serve no purpose with modern pads and materials.

neo_omega

the slots and the holes on the rotor are not for cleaning. It's funtion is to relief the gas product by the pad at high temp. the slot and holes are not for cooling. It's for gas relief.

outgassing occurs when the temperature of the pad is great enough for the bonding agents used in its manufacture to break down into gas (this is the "burnishing" process), in turn these gasses form a pneumatic boundary between the friction surfaces of the pad and the rotor. When outgassing occurs it will reduce stopping power.

So Slotted and Dilled are actually build for racing. Only racing will product high enough temperature for outgassing to occur.

DeNguyen, the brake system does help you stop faster. Yes, the less weight you have, the easier to stop. It's basic physics. But you have to decelerate your car. That's the pad, the rotor and the whole brake system for.

sunshine

iTrader: (3)

Go to KVRperformance.com
they have a good side by side compare of crossdrilled vs slotted

neo_omega

WOW, that comparison can't be any more wrong.

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.

Cooling is done by the "Vanes" not the holes or slots

95R2-89TII Ground Zero

Why not just get the best of both worlds. Cross-drilled and slotted rotors.

DamonB

Outgassing no longer exists with modern pad materials.

outgassing occurs when the temperature of the pad is great enough for the bonding agents used in its manufacture to break down into gas (this is the "burnishing" process), in turn these gasses form a pneumatic boundary between the friction surfaces of the pad and the rotor. When outgassing occurs it will reduce stopping power.[/QUOTE]

Yes, that is what caused outgassing in the old days. Not a problem anymore. Even if you insist it exists a slot will also provide a "pocket" to sweep the gases out without drilling holes in the rotor and sacrificing longevity, being prone to cracks or throwing away material in the rotor which you need.

So Slotted and Dilled are actually build for racing. Only racing will product high enough temperature for outgassing to occur.[/QUOTE]

Ever had the rotors warp on your daily commuter? You overheated them. You got them hot.

DeNguyen, the brake system does help you stop faster. Yes, the less weight you have, the easier to stop. It's basic physics. But you have to decelerate your car. That's the pad, the rotor and the whole brake system for. [/QUOTE]

Brakes do not stop cars! Tires do. You can have street tires and huge brakes. I will take slicks and small stockers. You'll lose. Once you have enough brake to lock the tire repeatedly over the course of a race, everything else is wasted. Racing brakes are bigger to

1) Provide more mechanical advantage to the wheel/tire (more efficient)

2) Provide more swept area (friction surface) for the pad which distributes heat more evenly (more efficient therfore making life easier on rotor AND pad)

3) The larger rotor provides more mass with which to absorb heat and dissipate it into the airstream; it provides a larger heat sink.

Physics. Conservation of Energy. A brake rotor and pad convert kinetic energy into heat. If the rotor can't itself get rid of the heat faster than it comes in it will destroy itself. The more mass you have (bigger rotor) the more heat you can convert and at the same time your deltas are not as large.

neo_omega

I didn't say the tire not for stopping. But I would like to see how you stop without your brake system

I do know out-gassing is not a big factor in modern day cars. But the slot and holes are not for cooling. It's for relief gas. Even there is no gas to relief

DamonB

You're right! Read closely "In some of the older pad compounds..." Older. Not modern. Old. Used to be. In the old days.

Cooling is done by the "Vanes" not the holes or slots
[/QUOTE]

Yep, cooling from the vanes. Slots are there to sweep the spent brake pad from the rotor. All that trash on your wheels? The slots keep it out of the area between the pad and rotor so the brake dust doesn't decrease initial bite.

martini

My rotors are cross pitted and slotted (EBC). I just put them on this weekend with some new pads. They bite hard.. Pictures coming soon.

neo_omega

The slots are not for cleaning the pad. It's for relief the gas. Your agurement is the modern pads don't havce gas. Yes it's ture they don't product gas. But the fact that they don't product gas now doesn't mean it will change the function of the slots and holes. And the function of them are relief gas. Not cooling or cleaning. Those just myths and misunderstanding of what the slots and holes do.

rswst8

hmm, i got slotted and cross drilled rotors on ebay, compared to most of the expensive mods for these cars, $135 rotors are pretty cheap

i did a few Porsche club driving schools last year and asked some of the guys about their cross drilled rotors, they said they had no problem with them cracking, and these cars are about the same weight as a 3rd gen...

i didn't realize those were cast and not drilled, i guess there's no one making cast rotors for the FD?

i'm just putting the rotors on now and will be coming to MADS with them in a month, maybe i'll crack them and only get a month of enjoyment out of them, but at least max will have to think twice the next time he sees a car with drilled rotors

if these crack, i guess i'll stick with slotted ones

DamonB

Do we agree that AP Racing supplies some of the most elite motorsports teams in the world and knows what they are talking about? From their website:

http://www.apracing.com/car/brakedisc/choice.htm

Grooved Discs : Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs.

HedgeHog

Neo_Omega: sometimes u hafta admit you're wrong. Slotted rotors are meant for deglazing the pads. The degassing is more of a side benefit not its intention.

DamonB

GRM wrote a great article on braking systems. I found it reprinted here: GRM brake primer

This is a MUST read; very informative yet easy to understand. Allow me to quote a small portion pertaining to discs:

Let’s look at some common rotor “modification” and “performance” upgrades that you may have been ex- posed to. We’ll try to separate the marketing from the engineering: Bigger rotors will make your friends think you are cool, bigger rotors look sexy, but bigger rotors do not stop the car. What a bigger rotor will do is lower the overall operating tempera- ture of the brakes—which is a GREAT idea IF your temperatures are caus- ing problems with other parts of the braking system. Take, for example, a Formula 500 racer, a small 800-pound, single-seat formula car. While the brakes are cer- tainly much smaller than those found on a 3000-pound GT1 Camaro, that does not necessarily mean that they need to be made larger. In fact, in- stalling a GT1 brake package onto our formula car would probably do more harm than good. That’s a lot of steel hanging on the wheel that needs to accelerate each time the gas pedal is pushed. So the motto of this story is bigger is better until your tempera- tures are under control. After that point, you are doing more harm than good, unless you really like the look. (And hey, some of us do.) Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the ‘40s and ‘50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as “gassing out.” These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of fric- tion. The holes were implemented to give the gasses somewhere to go. It was an effective solution, but today’s friction ma- terials do not exhibit the same gassing out phenomenon as the early pads. For this reason, the holes have car- ried over more as a design feature than a performance feature. Contrary to popular belief, they don’t lower tem- peratures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads—sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or Fl. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it. The one glaring exception here is in the rare situation where the rotors are so oversized that they need to be drilled like Swiss cheese. (Look at any performance motorcycle or lighter formula car, for an example.) While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remem- ber that nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operat- ing temperatures and longer brake pad life, at the expense of higher weight. It’s all about tradeoffs. Slotting rotors, on the other hand, might be a consideration if your sanc- tioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to re- duce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut prop- erly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)
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