MSCA

iTrader: (3)

Of course there are disadvantages to these kinds of performance rotors. First, it should be obvious to anyone that the swept area is reduced on a drilled rotor. This reduction in material can cause longer braking distances. The upside is that the rotors will dissipate heat better, which of course is often necessary for racing. There are other racing benefits as well (gassing, etc…) but I want to keep on the topic of street use. Either way, on the street it is pretty rare for someone to heat his brakes up to the point that they will fade due to heat.

Another drawback is cracking. It’s very rare to see a solid rotor crack. It’s not rare to see a drilled rotor crack due to thermal stress between the holes. There was a good article about these performance rotors in Car and Driver magazine a while ago.

Finally, drilled and slotted rotors have a sort of “cheesegrater” effect on your brake pads. They will wear out significantly faster than they would have on a solid rotor.


Do yourself a favor and stick to solid rotors if you don’t track your car. Other than looking pretty, there are not a whole lot of reasons to go with drilled/slotted rotors.

BTW, just in case anyone doesn’t know this, it’s a misconception that heat causes rotors to warp. The fact of the matter is that rotors almost NEVER warp in the first place. The pedal pulsations people feel is almost always uneven pad deposits on their rotors. They just assume that the rotors are warped because they feel the pulsations in the brake pedal.

Mike

iTrader: (1)

Even with a reduced swept area, I can 100% guarantee that you will till have enough braking power to activate ABS, even with full slicks. You may need a better pad.

On the street, a simple full ABS 70-0 stop will heat the OEM pads enough to fade them. The figure a bit higher for the factory option pads.

Cracking only happens when you hit extreme temperature changes.

Case in point: AMG's come with drilled rotors. Certainly, those AMGs are higher performance vehicles than our G37.... Hell, they offer a free AMG driving school to anyone who purchases an AMG.

No, they do not. A cheese grater has raised edges to dig into the cheese. A drilled/slotted rotor has the same surface height on either side of the given gap unless there is damage. If there is any actual "grating", you'd hear and feel it in the pedal, similar to an uneven pad deposit.
Why not? They look different and are CHEAPER than OEM replacements. Best of both worlds.
I beg to differ. Most people make the incorrect assumption, but I 100% guarantee that rotors will warp under the right conditions. I've probably cracked more rotors from warping (uneven cooling) than you've gone through in your lifetime.



TL;DR: If you don't like a sponsor's product, keep your negative comments to yourself or post it in another thread. Don't pollute their thread.

MSCA

iTrader: (3)

It's not just about braking power, it's also about heat dissipation. Reducing the swept area does nothing to help dissipate heat.

Not on my car, nor any that I've driven. If one hard stop from 70 miles per hour fades your brakes, then you've got some serious issues going on. It would take multiple repeated hard stops from that speed before any fading should occur.

That's correct. And when you have holes in the rotors, that's exactly where the cracks are most likely to develop. If you don't have any holes, cracks are much less likely to develop in the first place.

That's not a case in point. I'm not arguing that drilled rotors don't offer some advantages. I'm simply saying that they are more useful on track cars because of the disadvantages that go along with them. AMG is the high performance division of MB. MB owners who track their cars are more likely to buy AMGs. Makes perfect sense to me.

Yes, they absolutely do. Of course cheese graters have raised edges. I was using a euphemism. The effect is similar though. The information is out there for anyone to research for himself. It's a fact that drilled/slotted rotors cause pads to wear faster than solid rotors. It's not even debatable.

I never said that it's impossible to warp a rotor. But at the same time 99.9% of the time people think their rotors are warped, they are mistaken. It's almost ALWAYS uneven pad deposits that are causing pedal pulsations. This is true for both street driven vehicles and tracked vehicles. In fact, I've used my track pads (harder) to remove deposits left on my rotors from my street pads. It's actually a very easy way to correct pedal pulsations from uneven deposition.

Mike

iTrader: (1)

Slots and holes increase surface area. That is what dissipates heat. Holes also allow for extra air to move through vanes.
I don't get this. You claim to track your car, but you've never faded on OEM pads? Do you track on all season tires you street drive on?
Actually cracks typically appear right next to a vane. With a drilled rotor, microfractures propagate outward, but typically find their way to the base of a vane.
What advantage do they offer tracked cars? MB knows that the vast majority of AMG owners will never track the car.
If that were the case, you'd feel the grinding, and pads would wear out ridiculously quickly. Simply untrue.
Track pads are not harder. They are more abrasive at low temps. That is why the scrubbing works. Then again, if youre getting uneven pad deposits, you're doing something wrong (probably choosing the wrong pad for your driving habits and/or application).



With all your knowledge, please explain to me why I consistently crack BLANK rotors every 3-5 track days.

MSCA

iTrader: (3)

The reason I started this thread is to continue a debate that started in an inappropriate area of the forum. It would be great if a mod could move the posts out of that thread and into this one. Thanks.

Anyway, back to the subject. Many people mistakenly believe that their rotors are warped when they feel pulsations in their brake pedal. What's really happening (in just about every case) is brake pad material is unevenly distributed on the surface of the rotor is causing excessive lateral runout, which is why you're feeling pulsations in the brake pedal. The first step in being able to eliminate this problem from occuring/re-occuring is to understand how/why it happens in the first place.

Here are a few good links if you want to learn more:

Dali Racing : Library Article : Brake Rotor Shake Demystified

There's no such thing as 'warped' brake rotors - Orlando auto | Examiner.com

StopTech : Balanced Brake Upgrades

Raybestos Brake Tech School, Part One: Rotors Don't Warp | Police Fleet Manager Magazine

joo030879

iTrader: (3)

Above statement is true. However uneven pad deposits are not directly responsible for pedal pulsations. Uneven deposits on a rotor over longer period of use, makes surface of a rotor react different to heat, pressure, and pad wear.

For example if you wax only half surface on a table. You can not really tell by looking at them but other un-waxed surface will react different to the environment. For example moisture, humidity, heat, and etc.

Brake rotors warp due to the fact uneven deposits creates variations on a surface of a rotor. Reacting different to the environment thus ending up with commonly described as warped rotor. Some drivers will experience warped rotor as early as 10'000 miles or some will never experience at all. This all depends on a use, environment, and many other factors.

The driver who experiences warped rotor as early as 10'000 miles. There is something wrong with the rotor. Unfortunately rotors are not covered under warranty. Dealer will re-surface them. But the same vulnerable point on a rotor surface may re-appear after 5-10k of use.

Motorsports aids test of certain part in 1-2 hours. How they would end up in 30k miles over long period of time. All rotor makers know they will never come up with perfect rotor surface. Like wise when you look at a knife's surface under microscope they are not smooth. So they came up with slotting to keep moisture and dust off the rotor surface. Drilling to cool down. Or if they have little of both they will drill and slot rotors. It is hard to change tires when racing imagine changing rotors.

Well maybe for the drivers who experience warped rotor as early as 10k, instead of buying new sets at the dealer. Or re-surface them and go back ever 5-10k for another resurfacing. Buy less expensive aftermarket rotor that better suits your environment. And not worry about warped rotors for longer period of use.

Mike

iTrader: (1)

MSCA: You simply regurgitate information you read on the internet.

joo and I regularly track our cars. I have first hand experience with pretty much every aspect of what is being discussed in this thread. If you can prevent brake rotor warpage, please, patent the process. You will become an extremely wealthy individual.

I crack blank rotors on a regular basis. Why? Simply because of extreme heat cycling that results in warping. The uneven cooling causes a tension force radially, eventually causing the metal to pull itself apart, forming microfractures, and eventually cracking. It happens time and time again, not only to my car, but everyone, regardless of make or model.

If warping does not occur, well, why does nobody pull their parking brake coming off of the track? Because the uneven cooling will warp the rotor.

MSCA

iTrader: (3)

I've repaired more cars then you've owned or driven. This isn't information that I've "read on the internet", this is information that I've learned over the years from hands-on experience. I posted the links to some expert sites for your benefit so you can learn something insteading of thinking you know everything all the time. You can argue all you want, but the information is out there in black and white. Go argue with StopTech engineers if you still don't believe the facts.

I first starting tracking my cars in 1987. I started with a Mustang, but quickly moved to more suitable cars. My M3 has been my favorite track car to date. And just for the record, I have never tracked my G37 and I never will. It's 100% a street car.

As for preventing brake rotor warping.....you just don't get it. I've been saying that rotors don't warp in the first place and you want me to patent a process to prevent it? LOL, silly boy. I can't patent a process to prevent something that doesn't happen in the first place.

Cracking and warping are not the same thing. Are you saying that it is impossible to crack a rotor without warping it? LOL

What? LOL...is that what you really think? Some parking brakes are shoes (not pads) in the rear rotor hub. Don't make foolish blanket statements.

MSCA

iTrader: (3)

The problem is not warped rotors. Read the links I posted earlier for more detailed information. Uneven pad deposits is absolutely directly responsible for pedal pulsations.

I've experienced this first hand on more than one occasion. Have you ever seen a pad imprint on a rotor? Did you ever wonder why this happens?

MSCA

iTrader: (3)

This is perhaps your most ignorant statement in this thread. You've had a few winners before, but this one takes the cake!

Holes never increase surface area. The surface we're talking about is the friction surface of a rotor. Holes mean there is LESS surface area against the pads, not more. Heat dissipation is also increased with larger rotors (read: more mass), which should be obvious.

I don't track my G37. It's a street car.

I've seen hundreds of drilled rotors that were cracked between the holes. It's not uncommon at all, even on street driven cars.

MB also knows that their customers who do track their cars are MUCH more likely to buy an AMG product.

It's a known and accepted fact. No sense in debating it with you because you're not going to believe it no matter what I say. Again, the information is out there....look it up yourself or talk to people who actually know something about it.

Most race pads are in fact harder. But hardness is a relative term. Are we discussing surface hardness? Not really....it's more about the fact that most race pads contain a higher percentage of steel fibers and are therefore more abrasive. This is what makes them "harder" than typical street pads and that's exactly the reason why race pads can be used to "clean" deposits from street pads. So call it whatever you want, but it works. If a set of rotors were actually warped, swapping on race pads wouldn't cure pedal pulsations.

I can't explain why you do the stupid thing you do. LOL. Here's a better question: If you believe so much in drilled rotors, why on earth do you continue to use blank rotors when you crack them every few days? Are you a glutton for punishment?

Mike

iTrader: (1)

Clearly, you do not understand the difference between surface area and mass. Drilling and slotting reduce mass and increase surface area.

Increased mass allows for more heat absorbtion, while increased surface area allows for more heat dissipation.

Think of boiling water. if you have 50% more water, it takes 50% more heat to boil it. If you boil water in a sauce pan, it will cool much faster, and take more heat to boil it, than if you boil water in a pot because the surface area of water in the pan is larger than in a pot, even with the same volume; the water loses heat to evaporation over a larger surface area, requiring a larger heat source to boil.

You quote stoptech articles from their website. I am on a first name basis with the owner. We both instruct with STUSA.
This exact fact is why you don't get the cheesegrater effect with slotted and drilled rotors. Rotors are typically softer and less abrasive. Hardness has to do with scratch resistance (in laymen terms), while abrasion has to do with surface angles of the involved crystals. They're directly related, but not the same.

Not sure why you'd mess up pre-existing bedding by swapping just pads though. The proper method is to use a lathe, which I'm sure you have access to.
Because they are cheaper. Rotors are a wear and tear item, just like pads and tires. Improved cooling will not help me any with rotor longevity. Warmer weather will.

Funny how rotors pop more when its cooler.... oh wait, it goes back to that thermal cycling thing I was talking about...


What M3 do you track? What class do you compete in? Are you on bimmerforums? You should come out to the bimmerforums vs THQ event. The bimmerboys think they're fast enough to take us on our local tracks.

Legz

iTrader: (1)

There's a bit of tension, but quite a good read indeed!

joo030879

iTrader: (3)

MSCA, I did read first three articles you posted. I guess You did not understand the crucial part from StopTech article.

All or three articles I have read agrees on that Brake rotors does not warp. Or common myth a loop hole shape bending. And all first three are telling us about how to prevent those.

Does an average member who will never in his entire life needs to know what goes on a molecular level of a rotor "Myth Warps". Does an average member needs to know how to prevent them? Yes. Instead of saying brakes don't warp. Tell members they need to read those articles to learn how not to warp their rotors. Point them into right direction. Don't miss lead them.

NO, however does a member who warped his rotor needs to know why it happens. YES.

There are some crazy folks under rain passes splashing water out on the street just for fun of it. You claim you own an SUV, vast majority of crazy folks drive splashing water on an SUV. Are you one of them? Does that person needs know it is bad for his rotor YES. Well should he get slotted rotors to splash water without damaging his rotors? NO. It is stupid.

We do track our G and now treat rotors just as if they are pads. They are replacement parts. But when it happens to us it is no fun. There are some street driven G's that reports vibration, as early as 10K. Is it better for him to:

A. Get his rotor resurfaced, than go back after 5K miles for another.
B. Change to more expensive OEM Rotors.
C. Buy less expensive after market rotors that better suits his/her driving style, weather, environment etc.

Which one do you pick MSCA. Or is it Micro Soft Central America.

Motorsports is team sport. Engineers do listen to their driver, research and comes up with solutions. If you have repaired hundreds of cars in your entire life. Without listening to your customers (drivers). Without knowledge or proper research.

YOU AINT TOUCHING MY G.

TVPostSound

iTrader: (9)

If rotors don't warp, why did they wobble on my brake lathe when I was a brake and front end tech years ago??

Ok, maybe the word warp is wrong.

How about excessive runout caused by heat, is that better??

MSCA

iTrader: (3)

They "wobble" (which is really an incorrect term, BTW) due to uneven pad deposits on the rotors. You can measure the runout with a dial indicator. Most people incorrectly think that cutting the rotors is the only way to correct OOS runout. Yes, cutting will fix it, but so will scrubbing off the pad deposits. That fact proves that the metal isn't warped. If it were, then scrubbing wouldn't do anything to help.