Im sure that this subject has been talked about, as with most subjects. However, It never hurts to review.
Cross-drilled: Holes are drilled through the rotor to dissipate heat. Cross drilling is very effective for heat dissipation. It will prolong the life to the pads, rotors and improve stopping power. It also shed off water under-wet driving condition.
Slotted: A line cut on the surface of the rotors to dissipate heat and increase bite. Slotted rotors will bring up the operation temperature of the braking components much faster over cross-drilled, yet it dissipates the heat at the same time. The added bite will reduce the stopping distance. Slotted rotor does not scarify the structural integrity of the rotor. Zinc-Plating: Zinc plating is a chemical process that is applied onto most rotors to prevent rotors from rusting. This chemical plating process is usually available in black zinc, gold zinc, or silver zinc. Although the entire rotors is zinc plated, the zinc will only remain on areas that do not come into contact with the brake pads. When purchasing cross-drilled slotted rotors, always make sure that the seller offers zinc --------------------------------------------- Cross-drill and slot patterns are precisely CNC machines for perfect fit to OEM specs for use with OEM calipers and wheels so that no upgrades are needed. Cross-drilled and slotted rotors give the maximum braking performance under all necessary driving conditions. Precision machined holes or slots on the rotors will allow hot gases from brake pads to escape quickly to prevent skidding or locking up. The quick response from pads to rotors will allow for improvement in stopping power. In addition to performance, cross-drilled slotted rotor just look good.
Actually, this post is one of the biggest piles of BS that I have ever seen!
Cross-drilled: Years ago (in the 70's) drilling was used to relive a problem called "outgassing", which was caused by poor brake pad formulations. Since the 80s, better brake pad formulation has eliminated the need for drilled rotors. Contrarty to popular belief cross drilling is actually WORSE for heat handling than a solid rotor. The holes are pointing the wrong direction for cooling. Cooling holes need to be in the radial direction (like the spokes on a wheel), not axial. Some racing rotors are cross drilled for weight savings purposes, but these are known to be less durable than solid rotors. "Street" rotors such as the one shown in the above post are cross-drilled simply becacuse it looks cool. Drilled rotors are also prone to cracking. Note that a REAL drilled rotor (one that is drilled for weight savings) looks nothing like the picture shown by the OP post.
Slotted: Slotted rotors were also developed in the early years of performance disc brakes. The theory was that the groove would scrape the pad surface, reducing glazing. Slotted rotors do not warm up any faster than solid rotors. And furthermore, if they did, they would certainly not dissipate heat better. The claim that they come up to temperature faster yet cool more effectively at the same time is a paradox--whomever wrote that needs to go back to physics class! The slots in a slotted rotor are far too small to have an appereciable effect on surface area or mass, and therefore they have no significant affect on cooling or on weight savings. However, they DO create stress concentrations (areas where cracks can form) on your rotor surface.
Zinc Plating. This is just another fancy name for galvanizing. Sure, you can plate a rotor. However, the first time you brake, the brake pads will scour the plating off the braking surface. You might be able to keep the hub of the rotor from rusting, but you cannot affect the braking area itself.
"Caution on drilled rotors: There is a common mis-perception that rotors are drilled to improve cooling. The reduced mass of a drilled rotor will dissipate its retained heat quicker, but it also builds up heat at a much faster rate. The decision to use drilled rotors should be solely based on the merits of the lower rotating and unsprung weight, and not for improved cooling. It is not wise to use drilled rotors in sustained high heat on hard braking tracks unless the team budget affords a high frequency of rotor and brake pad replacement"
Further reading:
Clutches and Brakes by Orthwein Brake Design and Safety by Limpert Advanced Brake Technology, published by SAE
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ORIGINAL: CrazyAl Sure, you can plate a rotor. However, the first time you brake, the brake pads will scour the plating off the braking surface. You might be able to keep the hub of the rotor from rusting, but you cannot affect the braking area itself.
Thanks Al, thats good information on drilled and slotted rotors and makes sense. But I disagree with you on the zinc coating issue.
What zz mustang said:
quote:
the zinc will only remain on areas that do not come into contact with the brake pads.
I have often wondered what happens inside the slots and drilled holes after time. Do they become ugly rust collectors. If you want these rotors just for the look the zinc would help prevent rust in those areas.
It depends on how hard you brake, and how long you use the rotors. Brake rotors get very hot (especially if you are into performance driving), and even if the pads themselves don't touch the zinc in the holes, the coating can be "burned off" due to the heat.
Mind you, I'm not knocking zinc plating, there's nothing wrong with it. I am just irritated when companies hawk "zinc plating" as some kind of great reason to buy their rotors. The fact is that most rotors (even non-premium OEM replacements from the auto parts store) are either zinc, chromate, or chrome plated. And I also wanted to make it clear that the plating cannot stop most of your disc rusting simply becasue the main braking surface of your rotor (which is the most visible part of it) looses its coating after your first drive with the new rotors.
It's a bit like saying "Buy brand X soap! It comes in a bar!" ...well, so does most soap. There's nothing special about this.
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I think Brembo is a pretty reputable brand and on their FAQ they say:
What are the advantages of drilled and slotted discs? The main advantages of drilled and slotted discs are the same: increased brake "bite", and a continuous refreshing of the brake pad surface. Drilled discs have the additional advantage of being lighter and running cooler. However, there are certain pad materials that should not be used with a drilled disc.
Why use drilled or slotted discs?
Drilling or slotting discs aids the disc in several ways: The edges of the slots or holes continuously clean and refresh the pad surface as well as providing increased brake "bite". Additionally, they prevent gasses from collecting between the pad and disc interface. The disc is lightened, thereby decreasing its rotational inertia. Improved ventilation increases the disc's ability to shed heat, resulting in cooler operating temperatures
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Also, why do most, if not all, motorcycle I see use drilled rotors?
Brakes are important on a car... but they are phenomenally important on a motorcyle...
quote:
ORIGINAL: CrazyAl
Actually, this post is one of the biggest piles of BS that I have ever seen!
Cross-drilled: Years ago (in the 70's) drilling was used to relive a problem called "outgassing", which was caused by poor brake pad formulations. Since the 80s, better brake pad formulation has eliminated the need for drilled rotors. Contrarty to popular belief cross drilling is actually WORSE for heat handling than a solid rotor. The holes are pointing the wrong direction for cooling. Cooling holes need to be in the radial direction (like the spokes on a wheel), not axial. Some racing rotors are cross drilled for weight savings purposes, but these are known to be less durable than solid rotors. "Street" rotors such as the one shown in the above post are cross-drilled simply becacuse it looks cool. Drilled rotors are also prone to cracking. Note that a REAL drilled rotor (one that is drilled for weight savings) looks nothing like the picture shown by the OP post.
Slotted: Slotted rotors were also developed in the early years of performance disc brakes. The theory was that the groove would scrape the pad surface, reducing glazing. Slotted rotors do not warm up any faster than solid rotors. And furthermore, if they did, they would certainly not dissipate heat better. The claim that they come up to temperature faster yet cool more effectively at the same time is a paradox--whomever wrote that needs to go back to physics class! The slots in a slotted rotor are far too small to have an appereciable effect on surface area or mass, and therefore they have no significant affect on cooling or on weight savings. However, they DO create stress concentrations (areas where cracks can form) on your rotor surface.
Zinc Plating. This is just another fancy name for galvanizing. Sure, you can plate a rotor. However, the first time you brake, the brake pads will scour the plating off the braking surface. You might be able to keep the hub of the rotor from rusting, but you cannot affect the braking area itself.
"Caution on drilled rotors: There is a common mis-perception that rotors are drilled to improve cooling. The reduced mass of a drilled rotor will dissipate its retained heat quicker, but it also builds up heat at a much faster rate. The decision to use drilled rotors should be solely based on the merits of the lower rotating and unsprung weight, and not for improved cooling. It is not wise to use drilled rotors in sustained high heat on hard braking tracks unless the team budget affords a high frequency of rotor and brake pad replacement"
Further reading:
Clutches and Brakes by Orthwein Brake Design and Safety by Limpert Advanced Brake Technology, published by SAE
I think Brembo is a pretty reputable brand and on their FAQ they say: -----------
Also, why do most, if not all, motorcycle I see use drilled rotors?
Brakes are important on a car... but they are phenomenally important on a motorcyle...
Brembo is trying to sell you something, of course!! Several years ago I built and ran a brake dyno when I was in grad school. I have personally tested many different combinations of rotors (drilled/slotted/solid/dimpled) and various pad formulations. The research project was funded by one of the big automakers (I am contractually disallowed from revealing who) who wanted to study how to improve braking on their cars. The bottom line is that drilling and slotting had negligable effect on brake torque (braking power) or brake fade, except with the drilling was "extreme". In that case, the fade got worse, mean temps went way up, and the brake torque went down as the pads failed due to heat.
By the way, I know motorcycles well. I own three Ducatis and a Honda and I am a certified Ducati mechanic. I consult for two different aftermarket companies that specialize in sportsbike parts. Brakes are not any more important on a motorcycle than a car. Motorcycle brakes are much more lightly loaded than a car. A motorcycle weighs about 1/10th what a car weighs, yet it has only about half the pad area and 1/4 the thermal mass compared to a car, and very similar effective braking radius. The typical motorcycle has VERY good brakes because of this. Heck, that's why a motorcycle has a much shorter stopping distance than a car. To put this in perspective, if you were to put brakes that good on a car, it would be like putting brakes from 40,000 lb 18-wheeler on the family Honda.
Becasue the ratio of the braking surface and mass to the weight of the motorcycle is so good, motorcycle brake discs can be lightened by hole drilling in order to reduce rotating weight, which improves performance. On a motorcycle the loading is low enough that it's OK to drill the rotors without running into problems.
On the other hand, the brakes on a car are much more heavily loaded. This is why holes start becoming a problem, and why 99% of all cars on the road are running solid brake discs. The few cars that you see that come from the factory with drilled rotors are doing it for style, and they also have much shorter brake service interval compared to most cars. You know how fast a top-end Porsche goes through rotors?
If you want to really learn about this, check out the books I mentioned above. SAE has also published many papers on this as well. You can read them for free at your local university library.
Take it from someone who has spent 100's of hours running a brake dyno. If you want to improve your braking, here are your options:
1) You can increase clamping pressure of your calipers. This could mean a smaller bore master cylinder, calipers with a larger effective piston area, a higher brake pedal ratio, or stainless flex lines. These things all work to increase the pressure at the brake pad.
2) You can change the composition of the brake pad to increase friction where it contacts the rotor. A more agressive pad will deliver more brake torque. This is also a trade-off however. Agressive pads cause more rotor wear.
3) You can increase the diameter of the rotor. A larger diameter rotor has more brake torque than a smaller diameter rotor.
Fooling with slots, dimples, and holes is turd-polishing with modern pads and has no appreciable effect on brake torque. If you want a brake upgrade on a budget, get some more agressive pads and the stainless lines. If that's not good enough, you need to start looking for a "big brake kit" instead.
Now then, drilling DOES reduce the weight of the rotor, which reduces unsprung rotating weight. And that is a good thing. However, drilled rotors are also prone to cracking and are more likely to fade. You have to decide wether or not it's worth it based on the kind of driving that you do. Also note that "street" drilled rotors, especially the OEM-replacement type (like Power Stop) are drilled so little that you'd never notice the weight that was saved. These people are just out for your money.
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I can't even understand why this post was started. At least be right about the topic if you start it. I only know the basics about brakes and I knew that the first post was b/s....
ORIGINAL: CrazyAl Brembo is trying to sell you something, of course!!
Sounds to me that Wilwood is trying to sell an "anti-establishment" product to me.
I'll admit I don't know a thing about brakes so I'm no authority. However, do a search on cross-drilled brakes and 90+% of the manufacturers say that cross-drilled/slotted increases friction and reduces heat. It makes logical sense that a surface with holes in it, spinning, will cool quicker than a solid surface...
You've not provided me with any evidence (other then your word and a quote from Wilwood which I've countered with Brembo) to suggest why this isn't so.
And, while I have no reason to believe you haven't done some research yourself, it would be totally illogical to say that Brembo and the many other manufacturers who do this for a living haven't done just "a little" research themselves...
Your argument regarding motorcycles makes SOME sense. However, following your logic, it doesn't stand up to existential evidence. For example, why is it my Honda 1300C has one rotor up front and the 1800C has two rotors up front? Heck, why does ANY motorcycle have two rotors up front? If a car, which you argue has a heavier load on each disc brake, can get by with only ONE rotor per tire, then why is it the higher performance motorcycles would ever require TWO per tire?
Put another way, if a Honda CBR1000RR needs two brake rotors per tire for effective stopping then by your logic a Corvette Z06 should need at least two and more likely 4-5!!
What I would like to see, and have been unable to find, is the brake system for a NASCAR or Indycar race car. If they have solid rotors then I'll start to believe you. And that is presuming that they are not made of some exotic ceramic...
It comes down to this for me. Say I spend $250,000 on a Ferrari. It comes with cross-drilled rotors. You are telling me that if they were solid they would be better? I'm sure that if solid rotors were better, Ferrari would put the better rotors on their car...
< Message edited by timothyrw -- 1/13/2007 4:06:40 PM >
Here is some ACTUAL evidence everyone can consider.
Brembo designed the composite carbon/ceramic brake system for the Ferrari F2002 used in Formula 1 races. Those brakes were then put on the Ferrari Enzo.
ORIGINAL: timothyrw Is Wilwood giving their brakes away? Sounds to me that Wilwood is trying to sell an "anti-establishment" product to me.
No, they're not giving brakes away. However, Wilwood's main market is actual (non street legal) race cars--Nascar, Can Am, Outlaw, and so forth. "Street" use is a small portion of their business. They don't need to hawk their products as their market is already well established. Professional race teams use highly drilled rotors on their cars for weight savings purposes, and consequently they get people who want to use their racing rotors on street cars. This has lead to problems in which a customer uses racing brakes (which are intended for a lightweight stripped-down car, and frequent replacement) on a street car which is much heavier.
quote:
I'll admit I don't know a thing about brakes so I'm no authority. However, do a search on cross-drilled brakes and 90+% of the manufacturers say that cross-drilled/slotted increases friction and reduces heat. It makes logical sense that a surface with holes in it, spinning, will cool quicker than a solid surface...
Advertising is not exactly gospel. I see ads every day for stocks that are guaranteed to make me a millionaire overnight, and pills that will add inches to my johnson, but that doesn't mean that these things are true. Think about it. If cross-drilled rotors really were better than solid rotors, you would see much more of them on vehicles from the factory. 95% of this "cross drilling helps heat dissipation" BS comes from overseas vendors trying to sell people their snake-oil brake products. Auto makers such as Ford spend a lot of money enigneering their brake systems. They know what works and what doesn't.
As for the "logic" of the situation, that is what the marketing people are counting on to sell brakes. First off, look at one of these street-style drilled rotors like a Powerstop. Those holes are not even 1/4" in diameter and there aren't very many of them . Do you really think that an appreciable amount of air is going to move through those holes?
Let me explain in detail why the holes do not cool appreciably. When a brake disc is spinning, the hollow passages inside the rotor (the vanes and channels) act like a centrifugal pump. Air from the center of the disc (the hub area) is pulled through those channels and is blown out the "rim" of the rotor. This is how rotors cool themselves down. The interior surface area of these channels is very large, and the vanes themselves act like heat sink fins to carry heat into the air. When the disk is spinning, it literally PUMPS air through itself to cool itself down. Cheaper rotors have straight vanes in them becasue this design is easier to manufacture. Premium brake rotors have directional or curved rotors. Why? becasue just like the rotor in a proper pump, curved vanes are more efficient at moving the air through the rotor. When the rotor is spinning, air is moving in a radial direction (like spokes on a bicycle wheel). The drilled holes in a rotor are perpendicular to this direction--they are oriented axially, not radially. Consequently they are pointed the wrong direction for air to be flowing through them. If that doesn't make sense, think of it this way: Pretend you are trying to drive out of a small driveway that has a T-intersection with a very busy street. You cannot move very quickly becasue you have to wait for an opening in traffic before you can get out. Furthermore, the holes have very low surface area compared with the rest of the rotor. Think about the total effective area of a brake rotor: both sides (braking surface) plus the area of all those channels inside the rotor. Now think about the surface area of the inside of a hole. The additional surface area gain by drilling holes is a tiny fraction compared to the rest of the rotor.
quote:
You've not provided me with any evidence (other then your word and a quote from Wilwood which I've countered with Brembo) to suggest why this isn't so.
That is not entirely true. I have suggested three books, all of which are well regarded in the professional community and have withstood the scrutiny of countless engineers and scientists.
quote:
And, while I have no reason to believe you haven't done some research yourself, it would be totally illogical to say that Brembo and the many other manufacturers who do this for a living haven't done just "a little" research themselves...
Of course, Brembo et al have done their research. But their goals may be a lot different than yours or mine. Let's look at the claims made here. The OP post claims the reason for drilling rotors is to dissipate heat. Brembo says nothing about dissipating heat and instead says that the holes refresh the pad surface.
The OP post is simply wrong, and I have explained why and provided documentation to back it up. Brembo has a bit of point. Holes do cause some degree of scraping of the pad surface, and that can (slightly) improve friction if used with the right kind of pads. Now then, this also happens to shorten pad life becasue the pads are being constantly scraped. That is a tradeoff, just like the highly drilled race rotors.
If you get the highly drilled rotors, you do get some benefits: decreased weight and perhaps a small increase in pad friction. But you also have to replace your parts more frequently. That may or may not be OK with you.
quote:
Your argument regarding motorcycles makes SOME sense. However, following your logic, it doesn't stand up to existential evidence. For example, why is it my Honda 1300C has one rotor up front and the 1800C has two rotors up front? Heck, why does ANY motorcycle have two rotors up front? If a car, which you argue has a heavier load on each disc brake, can get by with only ONE rotor per tire, then why is it the higher performance motorcycles would ever require TWO per tire?
You are confusing what is needed to stop for general use with what is nice to have for performance situations. Your 1300C has one rotor becasue that is all that is needed for safe use of the motorcycle. The 1800C is an upgraded model which simply has better brakes than the 1300C. The 1800 doesn't NEED the better brakes. It just has them for better performance. This is very common in motorcycles. For example, with Ducatis there are various "grades" of each bike. The cheapest model variant is called the "Dark". Dark models typically have less expensive suspension components and they ususally only have one front brake disc. The standard models--which have exactly the same engine--have two brake discs. It's just a higher performing model. The same is true with the Mustangs. The GTs have larger brakes than the V6 models, despite being essentially the same weight.
quote:
Put another way, if a Honda CBR1000RR needs two brake rotors per tire for effective stopping then by your logic a Corvette Z06 should need at least two and more likely 4-5!!
The CBR1000RR doesn't need two brake discs at all. It simply has them as a performance upgrade. In fact, on some racetracks when hard braking is not needed, some riders remove the second brake disc for more weight savings.
And yes, for a Z06 to have the same braking as a CBR1000RR (assuming the tires hold, of course), it would need much more rotor area.
quote:
What I would like to
< Message edited by CrazyAl -- 1/13/2007 6:16:41 PM >
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Here is some ACTUAL evidence everyone can consider.
Perhaps my first post wasn't particularly clear. I am not saying that cross-drilled rotors don't have some advantages. They do. Drilled rotors can reduce rotating weight. I am saying that the original post by ZZ mustang is factually incorrect. The reason for cross-drilling is NOT for heat dissipation and it does NOT improve stopping power.
Cars like Ferraris have cross-drilled rotors for weight reduction purposes, and becasue of this they also have a much more frequent maintenance schedule.
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Crazy Al I think your posts are " sone of the biggest piles of BS that I have ever seen! "
But thanks for your opinion on my post.
ZZ, if I offended you, I apologize. I did not intend to call you names--in fact, I didn't even think that you wrote that post at all.
I thought your post was simply cut-and-pasted from somewhere else. The poor English of the post and the choice of wording makes it sound like it was written by a cheap foreign shop trying to hawk their products. And you know what? Google for the first sentance of your post and what do you find? That text is advertising garbage from an Ebay vendor selling cheap Chinese "performance rotors".
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Black 2006 GT Coupe Dynatech LT headers & X; Borla catback C&L CAI; 93 oct tune Full BMR, Spohn & Steeda suspension D-Specs; Alum driveshaft Second Skin Audio damping; Infinity spkrs; Goodyear Eagle F1 255F/295R - FR500 wheels
CrazyAl: Next to all the incredible info you continue to provide on this MF which helps us all so much... you know what I really admire about you? When people challenge you, particularly in a very unprofessional or immature way you simply ignore that behavior and stick with the subject matter. Don't ever change this way about you or leave this forum, because a few people don't appreciate you. I'm sure you already learned a long time ago that you will find that anywhere you go. You are extremely knowledgeable and inspiring and apprecaited by so many. Thanks again!
In years past, cross-drilling and/or slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads began to break down at extreme temperatures. This condition is often referred to as "green pad fade" or "outgassing". When it does occur, the driver still has a good firm brake pedal, but simply little or no friction. Since this normally happens only at temperatures witnessed in racing, this can be very exciting! However, with today´s race pad technology, ´outgassing´ is no longer much of a concern. When shopping for races pads, or even ultra-high performance road pads, look for the phrases, "dynamic surface treatment", "race ready", and/or, "pre-burnished". When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with ´outgassing´. Ironically more pedestrian pads used on most streetcars will still exhibit ´outgassing´, but only when used at temperatures normally only encountered on the racetrack. Although crossdrilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’s often wide-open wheel designs. Crossdrilling offers the greatest gas relief pathway, but creates potential "stress risers" from which cracks can occur. Baer´s rotors are cast with crossdrilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings.
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Slotting increases the bite of the pads and helps the car to decelerate more rapidly. The process doesn´t involve removing as much metal as cross drilling, so it doesn´t result in as great a weight saving. Slotting, however, is even more effective than cross drilling in combating the problem known as "out gassing". This occurs when, at very high braking temperatures, the bonding agents used in some brake pads produce a gas. Under extreme conditions, this gas can create a pneumatic cushion between pad and rotor, giving a driver a normal pedal feel but reducing the amount of friction being generated. The slots pump away this gas and restore full contact. The "micro-shaving" effect of the slots also serves to de-glaze the pads (this is why the edges of the slots on EradiSpeed rotors are not chamfered or "radiused"). It also tends to even out the wear across the brake pad faces, increasing the effective contact area. This can extend rotor life.
Printable Version
Slotted and drilled Rotors - 
