RE: Slotted and drilled Rotors
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RE: Slotted and drilled Rotors - 1/16/2007 4:15:39 AM
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ZZmustang
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BillsXchargerfund
You let it go. Like I said I don't comment on my own post just to bring it back, so the thread is coming back because people are talking about the subject. And you can Please feel free to add to the discussion, but keep it on-topic .
Crazyal
Your comments were very good, I especially liked your cut-n-paste and copies of different web sites. And the amount of time it took to gather that information for the people here , I’m sure, is appreciated and welcomed.
Being an engineer doesn't make you Divine, just as having a MD behind your name doesn't make you a good Doctor, It just says you have the schooling. Your opinions are valued and to some are written in stone, but to some others, your opinion are just that, Opinions. You made some very good points and I agree with most.
My opinion on drilled rotors and braking systems as a hole is this.
Drilled rotors do improve clamping ability of a brake pad against the rotor, But at what cost. The holes act like grinders to the pads and wear the pad to the point where a new set of pads last 1000-1500 miles. If I were to put drilled rotors on my vehicle I would chamfer the holes on the downside, but then what would be the point of the drilled holes. Braking dynamics has a lot to do with a number of variables, Road surface, tire pressure, Tire contact patch, tire compound, downforce on the tire, rotor material, rotor diameter, Caliper clamping patch, caliper location in reference to a vertical line and to that line forward or rearward of it, vehicle weight, liquid load weight, baffled liquid, (liquids don't react with the rest of the mass) head wind, tail wind, lateral force, speed of tire contact patch, and driver ability to react to change and apply brake pedal pressure accordingly. All these things contribute to the braking ability of a brakeing system. And Each one has different min/max in the overall performance of the system. So in the end, Slotted and drilled rotors do increase clamping ability of a caliper to rotor, but so does pushing a little harder on the pedal,
But that’s my opinion..
< Message edited by ZZmustang -- 1/16/2007 5:35:49 AM >
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RE: Slotted and drilled Rotors - 1/16/2007 8:30:39 AM
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CrazyAl
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ZZ,
What exactly do you mean by "improved clamping ability"? Are you talking about increasing brake torque, or are you talking about resistance to fade...what exactly?
The SAE test #J2430 is the current Brake Dyno standard used for cars & light trucks. This test method studies brake torque (this is what most people when when they discuss brake effectiveness), fade, cooling curves, and so on. The paper SAE J2430 Recommended Practice and Its Application for Characterizing Aftermarket Brake Friction Material Effectiveness by Trainor et al. describes an experiment in which several aftermarket brake rotors and pads were tested against OEM parts under this standard. Unfortunatley, the paper does not specify brand names. However the results are very clear:
1) Drilled and/or slotted rotors do not have a significant impact on brake torque (braking "power"), hot or cold.
2) Drilled and/or slotted rotors either have no measureable effect on fade, or they demonstrate worse fade characteristics than OEM.
3) Drilled and/or slotted rotors have the same cooling curve as OEM.
4) Various aftermarket PADS do demonstrate significant increases in brake torque, hot and cold.
Keep in mind that this paper tested rotors of the same size. In other words, it did not concern "big brake kits".
The SAE test #J661 is an older standard which concerns the effectiveness and also the durability of brake linings: including disc brake pads and drum brake shoes. The Limpert book I mentioned in the very first post I made describes the effect of slotted rotors on brake pad life using the J661 test. While the example given does not discuss the exact pad they used, we can assume it is an OEM-type pad, not a performance pad. They did indeed find decreased pad life. However, the lifetime was shifted from 41,000 miles with the OEM rotor to 28,000 with the slotted rotor. Again, this was with a OEM-sized drilled rotor. Of course, you can expect reduced brake pad life with drilled/slotted rotors, but according to this test data you should be expecting far more service life than 1500 miles, at least with an OEM type of pad. Many performance pads, especially true race pads, have a far lower durability than street use pads.
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RE: Slotted and drilled Rotors - 1/16/2007 9:28:05 AM
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ZZmustang
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Crazy al
I'll try to answer you question, keep in mind , I don't think slotted and drilled rotors are any good on the street.
Improved clamping ability, OK, Lets say the vehicle weighed 1,000,000 lbs so the wheel is not going to slide when brakes are applied. Then rubbing a brake pad against a drilled surface would act like a grinder to the pad, The pad would push against the edge of the hole taking off a small slice of the pad as the pad crossed over the edge of the hole, that process would in effect cause the pad to be ruffed which would make for more friction between the pad and the surface of the rotor without holes, there’s evidence of this in your own statements, "Of course, you can expect reduced brake pad life with drilled/slotted rotors" Now just why would a pad have reduced life? could it be the roughing of the pad from the holes?
The society of automotive engineers (SAE) is the industry standard for a lot of automotive products, However there testing is not all inclusive, they have a very controlled environment and have virtually no variables.
i.e.
your #1. "Drilled and/or slotted rotors do not have a significant impact on brake torque (braking "power"), hot or cold.
I would have to see the test, but I would say , What does "significant" mean? and what pressure is applied to the pad in each test, and what load is applied to the rotor for brake resistance. . If you have a free wheeling rotor and test a slotted rotor and a unslotted rotor there will be no difference, but that’s not a real test, there is weight behind the rotation of a rotor.
If you have a rotors that can not be stopped , slotted and non slotted, the pressure applied to the pedal will be less on the slotted rotor , to achieve the same force backward on the rotor. I guess it would be better to say drag. With non stoppable rotors, a slotted rotor will have more drag on it than a non slotted rotor for a given amount of pressure applied to the pedal.
Or , again, why would, "Of course, you can expect reduced brake pad life with drilled/slotted rotors" The force required to remove brake pad life has to go somewhere, wouldn't you say?
2, 3, and 4, I agree with. That don't make them true, it's just that I agree.
and lastly
The SAE test #J661 " They did indeed find decreased pad life" Again , where did the energy go that caused the decreased pad life? You being an engineer have to agree that pad life and stopping friction have to be related, the more you reduce pad life the more friction has to be there, if the materials are the same.
I’m just glade we can discuss this reasonably
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RE: Slotted and drilled Rotors - 1/16/2007 11:44:22 AM
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CrazyAl
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You are correct in principle, that the "scrubbing" action of a drilled or slotted rotor does indeed take some energy out of the system. The problem, however, is that this is a very small amount of energy. It's a bit like washing and waxing your car before going to the track to decrease air resistance....or going to the bathroom first to decrease the weight of the vehicle. Technically these things do have an effect. However the effect is so small it is negligeable.
I'll explain the details behind that but first I'll answer your question about the brake testing.
The SAE J2430 standard is very extensive. You can read about it here: http://www.linktestlab.com/Brochure%20PDFs/B.E.E.P.%20web%20procedure.pdf
As you can see, it includes braking at high speeds, slow speeds, repeated braking, cooling, hot braking, burnishing, and so on.
The test is performed on a brake dyno. A brake dyno has a very large electric motor which spins the brake disc. This motor is so large that the rotor is unstoppable by the brakes under test. (When I ran one several years ago we used a motor with 4500 ft-lb of torque. We had to have the city rewire part of the building in order to power it) The rotor is spun by this motor at a constant speed. The caliper is actuated with a hydraulic pump, so the pressure is even and controllable. A device called a load cell is used to measure the brake torque, and several thermometers track the temperature of the rotor, caliper, pads, and so on. This test standard is not a simple "freewheeling rotor" test. The rotor is loaded, just like on an actual car.
Now, down to the details. When you say "The pad would push against the edge of the hole taking off a small slice of the pad as the pad crossed over the edge of the hole, that process would in effect cause the pad to be ruffed which would make for more friction between the pad and the surface of the rotor", this does indeed occur--and you're right--that is where the extra pad wear comes from.. However, the extra force that this generates is extremely small. Pad wear occurs simply becasue over many tens of thousands of revoloutions, this starts to add up. In the aforementioned paper, the change in mu (coefficient of friction) from switching between solid discs and slotted discs (all other variables constant) was only two-onehundredths of one percent! The maximum recorded improvement was four one-hundredths of one percent! A similar set of tests is discussed in the Advanced Brake Systems book, and their recorded results were even worse--and their work covered thirteen different rotors!
This is what I mean by "significant". If I told you, "this mod will add 0.04 percent to your braking" would you buy it? Or an engine mod that would give you 0.04% more HP? That would be +0.12 HP if we assume 300 stock. What If I sold you weight loss pills that promised to drop your weight from 180 pounds to 179.928 pounds instead?
To put this in perspective, in the aforementioned book they recorded an improvement of 31.6% when they switched from an 11" test rotor to a 14" test rotor (all other variables unchanged). Various pad changes had improvements in brake torque ranging from 4.1% to over 18%. But the switch from solid to drilled recorded a maximum improvement of only 0.04%.
The data clearly indicates that same-size drilled rotors have NO appreciable effect on braking effectiveness. If you would like to see the tests, have a look at the books that I have referred you to.
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RE: Slotted and drilled Rotors - 1/16/2007 12:54:53 PM
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wingman75
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Very impressive Al, I've learned a lot from this disscussion. While we have your attention can I ask a question unrelated to slotted and drilled rotors? I would like to get rid of some of the brake dust and improve my cars stopping performance without resorting to a larger brake kit. I do think the stockers are pretty good. I am considering ceramic pads and would like to know if you think they are really any good. I'm thinking of purchasing Hawks pads... I've heard they make good products.
Thanks Al
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RE: Slotted and drilled Rotors - 1/16/2007 12:56:58 PM
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ZZmustang
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I think we are just going to have to disagree.
Your example of waxing you car to decrease air resistance is not accurate, otherwise a gulf ball would be smooth and waxed, The dimpling makes it fly further not a smooth surface. Turbulence on the leading edge lessons drag.
You think the scrubbing" action of a drilled or slotted rotor is a very small amount of energy and is negligible.
I think the action is much more and would wear the pads much more quickly because of it. And also much more braking ability.
I’m not ever going to use them, so I'm beating a dead horse. The information is on the thread for anyone to read and judge for themselves and make there own dissension.
Ron
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RE: Slotted and drilled Rotors - 1/16/2007 1:38:08 PM
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CrazyAl
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Everyone is welcome to disagree. However, extensive and repeated research clearly shows that the "scrubbing" action is essentially non-existant. The data is very clear. If you would like to ignore that, it's your choice. If you believe otherwise, please post some tests that support your claim. I have already posted several peer-reviewed publications that support mine.
A golf ball does indeed fly farther becasue of dimples due to the boundry layer effect. The boundry layer creates additional lift which helps keep the ball aloft. It also reduces wake turbulence. However, these aerodynamic properties are unique to spheres. On non-sphere objects such as cars and airplanes this does not occur, otherwise airplanes and autos (and missiles and bullets and high-speed trains....) would be dimpled too. The car-waxing example is perfectly valid. Professional race teams do make sure their cars are super clean before every race. Perhaps that last 1/100th of a second will get them a win. Even if you don't belive that example, the bathroom-before-race example still holds. The example was just to illustrate an example to fully help people fully appreciate the futility of such a small performance gain.
Wingman, I have not run ceramic pads on a performance car so I have no personal experience to relate that is 100% specific. However, I do have experience with various Hawk pads, and I have found them to be high quality products. I am running the HPS pads right now (not ceramic) and I am very happy with them. They are clearly superior to OEM. I check my rotor runout and wear as part of my routine maintenance on the car and I have not seen any problems with excessive wear on either the pads or the rotors.
Ceramic pads are harder than most other formulations so they wear less and generate less dust. Also, their dust particles tend to be smaller than those shed from conventional organic or semi-metallic pads, so what dust they do produce is harder to see. Furthermore, some ceramic formulations don't contain iron, or contain very little, which means your brake dust rusts less due to no iron from the pads. (Most rotors are cast iron, so you always get some iron dust from the rotors). On my Explorer I ran Akebono ceramic pads for about 60,000 miles and I had no noticeable dust and excellent braking performance from them. The previous pads (Ford brand...installed by the dealer) were quite bad about brake dust. The Akebonos were quieter, had better braking performance, and had no noticeable dust. Of course, this wasn't a "performance vehicle" and never went to the track or the strip, but in normal street driving & some towing they performed very well. I would not hesitate to buy them again.
There is a lot of anecdotal "evidence" regarding the low-dust nature of the ceramic pads, but there is no standardized test method for comparing brake pad dust generation and visibility. Perhaps in the future we will see this quantified?
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RE: Slotted and drilled Rotors - 1/16/2007 4:04:51 PM
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ZZmustang
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Crazy al
The data is not clear at all except that you say its clear if you want to believe that the data is clear be my guest.
A study says that scrubbing" action is essentially non-existant, so therefore it's non existent? Id have to see that with my eyes, it's nothing personal, it's just I seen a guy make a girl disappear before and people will say and do almost anything to get there name out there, including slant a report to whatever side they want. (the missing link)
And the boundary layer doesn't just apply to spheres, that’s the reason they Neural(sp) the insides of intake ports on heads. and it would apply to any surface that has an angle to wind surface.
and your go to the bathroom-before-race example . is just an example in your eyes. I would think it would be more like taking 15 gal of fuel out of the car before you raced.
You know, a brick is a brick even without a study that says it's a brick.
I don't read a study and conclude that this is the absolute truth, Other wise Columbus would have fallen off the end of the world.
And Galileo would not have been denounced by Church officials , who offered Galileo an option for the avoidance of being burned at the stake for church heresy. Denouncing his beliefs in a Copernican "sun-centered" universe, Galileo chose being imprisoned in his own home (and later in homes of his friends) for the remainder of his life.
Chuck Yeager would have never broken the sound barrier. A 10 second quarter mile run is imposable, an so on. Studies are just information, And some well intended studies are just not correct.
It's been nice discussing this with you and lets NOT do this again. You can have the last word if you like but I’m done.
Thanks
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RE: Slotted and drilled Rotors - 1/16/2007 5:47:01 PM
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Sleeper05
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quote:
ORIGINAL: ZZmustang
I think we are just going to have to disagree.
Your example of waxing you car to decrease air resistance is not accurate, otherwise a gulf ball would be smooth and waxed, The dimpling makes it fly further not a smooth surface. Turbulence on the leading edge lessons drag.
You think the scrubbing" action of a drilled or slotted rotor is a very small amount of energy and is negligible.
I think the action is much more and would wear the pads much more quickly because of it. And also much more braking ability.
I’m not ever going to use them, so I'm beating a dead horse. The information is on the thread for anyone to read and judge for themselves and make there own dissension.
Ron
Being a golfer since I was 5 and a 1.9 handicap, captain of my varsity team, ect, blah blah, I have to comment on that!
The dimples on a golf ball do DECREASE range of a shot dramatically, and ON PURPOSE. If you have ever hit balls at a range that are all worn down (and somehow not yet duds), you will notice that they fly much more aggressively, and at a lower trajectory. The purpose of the dimples is to CATCH air to increase the distance travelled in the air and maximize the angle of approach, INCREASE spin, and PROVIDE control of the motion of a ball both through the air and when it lands. Than way, I can hit a specific club a specific way and have a driver go 320yards with a slight right-to-left draw that lands and bounces hard, then a 120 yard pitching wedge with a slight left-to-right fade and a steep approach angle and spin it off of the hill on the green over to the pin placement...all with the same golf ball.
The amount of scrubbing does not necessarily mean the amount of braking power. Two surfaces with a higher coefficient of kinetic friction but much great density will grip harder and last longer than ones less dense that scrub together more.
< Message edited by Sleeper05 -- 1/16/2007 5:50:51 PM >
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RE: Slotted and drilled Rotors - 1/16/2007 8:17:28 PM
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Sprzout
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quote:
ORIGINAL: wingman75
quote:
ORIGINAL: xbone
Maybe try ceramic brake pads, they are only 70 bucks and worth their weight in gold for no more black dust, and i think they are alot easier on the rotors too. I love mine, it stops better and no dust.
I would like to get rid of the brake dust too. The worst part of cleaning is tring to get the dust out from behind the spokes. What brand pads are yours and where did you get them.
Thanks
My dad and I put EBC brake pads on his F150 and on my old Saturn...Still got some slight dirt on the front wheels, but not NEARLY as bad as some of the others, and the GreenStuffs provide a better amount of grip once they were broken in.
The only problems with them is that they squealed REALLY bad in the F150 until the initial "coating" was worn off of the pad (apparently there's some sort of special conditioner that's on the front of the pad, and is noted as such in the install directions included in the box). Some of that, I will attribute to the anti-squeal gunk not being given enough time to set up, but now the pads work really well.
And back to the real topic at hand, the cross drilled/slotted rotors:
I will agree that cross drilling rotors and slotting rotors makes them more brittle; I've seen numerous rotors that have cracked from heavy braking on the autocross tracks. That being said, though, I think that the rotors that are engineered for the high performance cars are done so to help the car stop better. Otherwise, why would Ferrari, Ford's GT, and numerous Porsche models have cross drilled or slotted rotors?
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RE: Slotted and drilled Rotors - 1/16/2007 8:39:11 PM
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CrazyAl
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quote:
ORIGINAL: Sprzout
My dad and I put EBC brake pads on his F150 and on my old Saturn...Still got some slight dirt on the front wheels, but not NEARLY as bad as some of the others, and the GreenStuffs provide a better amount of grip once they were broken in.
The EBCs are great pads. I have had good luck with them as well. I found that the proper bedding procedure greatly helps with the noise.
quote:
And back to the real topic at hand, the cross drilled/slotted rotors:
I will agree that cross drilling rotors and slotting rotors makes them more brittle; I've seen numerous rotors that have cracked from heavy braking on the autocross tracks. That being said, though, I think that the rotors that are engineered for the high performance cars are done so to help the car stop better. Otherwise, why would Ferrari, Ford's GT, and numerous Porsche models have cross drilled or slotted rotors?
The overall rotor design is, in fact, engineered to help the car stop better. The larger diameter and the vane design improves brake torque and fade resistance respectively. The drilling is used to fight the weight gain that would otherwise accompany a large rotor like that.
Cars like those you mention have very effective brakes becasue they are LARGE. The cross-drilling lightens the rotor to reduce the inertial load of the big brake disc and it looks good too. That, and as we have discussed, the slotting helps to fight glazing.
The cross-drilling does not give a Ferrari its awesome braking. The giant rotors and calipers do that. The cross-drilling allows them to use such a large rotor without incurring a big performance loss due to added rotating weight.
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RE: Slotted and drilled Rotors - 1/17/2007 5:19:54 PM
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JimsGT
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quote:
ORIGINAL: ZZmustang
Jim GT
Thanks. Thats the way to have a discussion, Talk about it, give some facts, give your opinion and thats it, No name calling no post bashing.
You Da Man Jim
LOL, thanks ZZ! I got alot of practice when I was on the corvetteforum.com !!! (You think this is bad???LOL)
To each his own, right? Run drilled, slotted, stock, whatever........! Its what you like!!! Jeez!
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RE: Slotted and drilled Rotors - 1/17/2007 9:36:18 PM
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gidyup
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This post is somewhere between a very interesting and informative discussion on brake design...and the Donald Trump/Rosie O'Donnell feud.
...but I have learned a lot about brakes.
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RE: Slotted and drilled Rotors - 1/17/2007 10:03:36 PM
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Buckman
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Crazy Al, thanks for the info on brakes, I have gleaned a lot of info from it.
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RE: Slotted and drilled Rotors - 1/18/2007 12:06:22 AM
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RodeoFlyer
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I look at it this way - NOTHING that increases performance in any area of the car is cheap. If slotted rotors were worth a whole lot they wouldn't be cheap. I only have them because I thrashed my factory ones and I got them below retail.
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RE: Slotted and drilled Rotors - 1/27/2007 8:03:47 PM
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rygenstormlocke
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IMO, this thread should be a sticky, or linked too from a sticky with useful links. Al: An exceptional read, and this ties into shops I've spoken with that are on the same page as you. Reading this detailed thread re-confirmed in more detail what I have been told by other sources. Thanks man.
I'm book marking this one.
Cheers.
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RE: Slotted and drilled Rotors - 1/27/2007 9:20:01 PM
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ranebowcyxx
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Agreed with the guy above :)
My two cents of this thread comes from the fact someone mentioned motorcycles, back in the 80s we would drill out our rotors to improve braking when the rotor(s) got wet, ie getting caught in the rain. Other than that I never thought there was any other advantage to them, oh, they look cool too.
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