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There is a debate in the car community as to whether drilled and/or slotted rotors actually cool the rotors more effectively.

Sportbikes almost always have drilled rotors, so there must be something to that, no?
 

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Well I can touch my drilled/slotted rotors @ 15 mins after I drive.
With the stock rotors they took 2+ hours to cool.
So I would agree drilled/slotted cool faster
 

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I suspect both methods allow for greater heat dissipation over non-drilled/slotted rotors. I guess the debate would be which method is more effective as each has it's own benefits. I am not a mechanical engineer but I would venture a guess that slotted rotors may be cooler in that less contact (friction) made between pad and rotor.
 

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Slots and holes can help sweep debris away from the pad, and gives water a place to go when squeezing the pad in the rain. My 76 Jeep has cooling slots sandwiched or cast-in between the rotors, but the rotor sure is heavy. Of course, the less material, the lighter the rotor. It is unsprung weight.
 

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I dont know the technical name for it but the main reason for the slots or holes is to actually let the superheated air escape. If they werent there you can actually (under racing or very hard braking conditions) have a air gap between your pads and rotors and have little stopping power. Thats also a big part of brake fade is the hot gasses produced with all that friction pushing the pads off the rotors.
 

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V-Twin Moddin
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Very close... slotting is to allow the gases to escape off the brake surface and the cross drilling is meant to increase surface area to allow for faster cooling therefor causing less brake fade due to excessive heat...

This info is straight from a brake dyno tech at a major braking industry provider...
 

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I did extensive research into the subject since I was replacing a set of pads on an F-body and concluded they're a waste of money unless you're going for bling. Brakes are almost never the issue, its the grip on the road that's the factor in how quickly/well you stop. The exceptions appear to be track days since high speeds and frequent use of the brakes can result in warping.

If you do opt for the drilled, be certain they're camfered because stress cracks are quite common place. Remember that either (or both) holes and slotting will wear the pads faster.

My sources were forums for autocross, street performance enthusiasts, and drag racing.

:2cents:
 

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V-Twin Moddin
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I beg to differ... I wish some of my cars had the cross drilled or slotted... because I've warped alot of rotors on cars with heavy braking during rush hour commutes!
 

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Gas, my thoughts are that you bought the wrong brand then. The OEM rotors that came on our F-body (<3k pounds weight) did warp w/in 20k miles. Rather than fight the dealership for another pair that would warp again, we did lots of research to find a brand that was known, for that application, not to warp. No problems now, and we use the brakes pretty roughly. Race pads, blanks from Autozone @ ~$30ea in stop and go, high speed stopping, and lots of cornered stopping.

The pads have a serious impact on rotor heat, too. Many have suggested ceramic as part of the solution, though I've never had an issue with semi-mets.
 

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OK....a topic I might just know something about. Brake design isn't as clear cut and simple as you guys are trying to make it. First off, chamfering of pads is a performance thing and it's mostly done for noise issues...why, chamfering costs money to cut them plus it's a waste of material. OK, so, that's the jist on pads...now to rotors. Drilled and or slotted rotors is a performance issue as well and is a complete waste on your everyday cage. Why did your rotors warp...because they were developed wrong. Here in the industry, we don't drill them unless it's for an extreme performance situation....it costs too much money. Instead, we vent rotors. Also, vehicle cooling characteristics goes into this as well. If a brake manufacturer can have a single solid disc, they will but generally, what you'll see on most cages is vented rotors (2 rotor surfaces with fins inbetween...venting). These cool much better then solid discs. OK, back to drilling, much design and work also goes into this and it's all about performance and cooling. They don't just drill for cooling because too much drilling or the wrong patterns will affect performance (things like stopping distance, fade, etc.). OK, I'll stop there for now before I go any further but keep the questions coming and I can answer more if needed. At the end of the day....spending the money for drilled or slotted rotors only make sense on high performance applications. On your cage.....WASTE OF MONEY.

Chev....over and out.

Oh yeah, been working in the brake industry doing development for more then 7 years here in Detroit for the #1 brake manufacturer in the world.
 

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NP Jeeps. If anyone wants any more brake advice, click over to the WOS board as I'm probably getting banned here soon for voicing my opinion. I'd be more then happy to answer any of your brake questions. Or, you can email me at [email protected]
 

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V-Twin Moddin
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You all have good points and I'm interested in the replies...
 

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I presume the venting you're referring to are both the design of the vanes plus the possibility of two-piece rotors. In my research and emails to the major aftermarket companies (Brembo is an example) I found none made two-piece blanks but that the two-piece slotted/drilled were easily available. But as already noted, only used in quite extreme circumstances or because "the most expensive is the best, right?" mentality.

As for bikes, I presume you're saying they do serve value. Is that right? I guess with the lower vehicle weight and reduced friction surface of the wheels, it would seem to me that brake slotting and drilling would be pretty irrelevant since your limiting factor is the amount you can effectively reverse the momentum without going backside up.

If you can stoppie a bike, do you really need better brakes for daily driver apps? Why? If not, is the heat dissipation in racing the only motivator to slotting/drilling? This seems somewhat logical to me, but let me have it :bluemc:
 

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Correct on the drilled rotors for motorcycle apps....I totally agree. When I mentioned 2 brake plates (2 piece rotors), let me clearify, they're not 2 pieces really. They are vented rotors, meaning the actualy break plates are 2 different discs (essentially) connected by fins. Yes, fin design, number of fins, plays a huge role in cooling. Most rotors on the front of your cage will be vented rotors of this nature (that I speak of).
 

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Let me add to this...yes, big time value in motorcycles. Wear isn't an issue but heat obviously is. If rotors on bikes were solid, they would heat up really quick, especially on sportbikes, because the rotor surface is so small with so much energy (heat) going into them. Not to mention, this added heat during long periods creates brake fade and in this situation (small rotors), would result in warping of the rotors also.
 

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kanwisch said:
.

As for bikes, I presume you're saying they do serve value. Is that right? I guess with the lower vehicle weight and reduced friction surface of the wheels, it would seem to me that brake slotting and drilling would be pretty irrelevant since your limiting factor is the amount you can effectively reverse the momentum without going backside up.

If you can stoppie a bike, do you really need better brakes for daily driver apps? Why? If not, is the heat dissipation in racing the only motivator to slotting/drilling? This seems somewhat logical to me, but let me have it :bluemc:
OK, I think this post will finally cover everything I'm trying to say. Yes, you are right on both accounts. Drilling and slotting of rotors is a heat thing, patterns of drilling can affect heat too but a lot of times, it's what looks cool that they go with but yes, it's a heat thing.

All in all in motorcycles, break wear isn't an issue. The are designed with heat, stopping power, and brake fade in mind.
 

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With all this braking knowledge, let me ask... When Buell went to the perimiter brakes on thier firebolt, they sited the larger surface area as the reason and a performance boost. But all the testing mags have done has proven them to be good enough if not merely adequit (sp?) It the Buell design a sound idea for brakes but executed pooly or it it a bad idea to begin with. Because it would seem the heat would dissipate better when the work is spread over such a large area. it should work better than it does.
 

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V-Twin Moddin
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Very interesting.... good inputs...
 
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