Slotted and drilled Rotors
01-13-2007, 11:07 AM
#1
Banned
Thread Starter
Join Date: Jan 2007
Posts: 956
Slotted and drilled Rotors
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 availablein 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.
[IMG]local://upfiles/58274/363DB025E57B4C6E8CF4CE9AA495ED42.jpg[/IMG]
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 availablein 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.
[IMG]local://upfiles/58274/363DB025E57B4C6E8CF4CE9AA495ED42.jpg[/IMG]
01-13-2007, 12:37 PM
#2
5th Gear Member
Join Date: Mar 2006
Location:
Posts: 2,544
RE: Slotted and drilled Rotors
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 arepointing the wrong direction for cooling. Coolingholes need to bein 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 discbrakes. 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 timeis 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.
Read the truth straight from Wilwood: http://www.wilwood.com/Centers/Infor..._answer/07.asp
In their installation notes, they go on to say:
"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
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 arepointing the wrong direction for cooling. Coolingholes need to bein 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 discbrakes. 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 timeis 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.
Read the truth straight from Wilwood: http://www.wilwood.com/Centers/Infor..._answer/07.asp
In their installation notes, they go on to say:
"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
01-13-2007, 01:34 PM
#3
5th Gear Member
Join Date: Jun 2006
Location: Sterling Heights, MI
Posts: 3,792
RE: Slotted and drilled Rotors
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.
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.
What zz mustang said:
the zinc will only remain on areas that do not come into contact with the brake pads.
01-13-2007, 01:55 PM
#4
5th Gear Member
Join Date: Mar 2006
Location:
Posts: 2,544
RE: Slotted and drilled Rotors
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.
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.
01-13-2007, 03:49 PM
#6
3rd Gear Member
Join Date: Sep 2006
Location: Indianapolis
Posts: 770
RE: Slotted and drilled Rotors
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
-----------
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...
[/align]
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
-----------
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...
[/align]
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 arepointing the wrong direction for cooling. Coolingholes need to bein 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 discbrakes. 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 timeis 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.
Read the truth straight from Wilwood: http://www.wilwood.com/Centers/Infor..._answer/07.asp
In their installation notes, they go on to say:
"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
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 arepointing the wrong direction for cooling. Coolingholes need to bein 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 discbrakes. 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 timeis 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.
Read the truth straight from Wilwood: http://www.wilwood.com/Centers/Infor..._answer/07.asp
In their installation notes, they go on to say:
"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
01-13-2007, 03:53 PM
#7
2nd Gear Member
Join Date: Feb 2006
Location:
Posts: 396
RE: Slotted and drilled Rotors
01-13-2007, 04:22 PM
#8
5th Gear Member
Join Date: Mar 2006
Location:
Posts: 2,544
RE: Slotted and drilled Rotors
ORIGINAL: timothyrw
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...
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...
By the way, I know motorcycles well. I own three Ducatis and a Hondaand 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 loadedthan a car. A motorcycle weighs about 1/10th what a car weighs, yet it has only about half the pad area and1/4 the thermal masscompared to a car, and very similar effective braking radius. The typical motorcycle has VERY good brakes because of this. Heck, that's why a motorcyclehasa muchshorter 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 puttingbrakes from40,000 lb18-wheeleron 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 atop-end Porschegoes 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 isturd-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.
01-13-2007, 05:06 PM
#9
4th Gear Member
Join Date: May 2006
Location: Nutley NJ
Posts: 1,207
RE: Slotted and drilled Rotors
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 andI knew that the first post was b/s....
01-13-2007, 05:33 PM
#10
3rd Gear Member
Join Date: Sep 2006
Location: Indianapolis
Posts: 770
RE: Slotted and drilled Rotors
IsWilwood giving their brakes away?
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 makesSOME 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 doesANY motorcycle have two rotors up front? If a car, which you argue has a heavier load on each disc brake, can get by with onlyONE rotor per tire, then why is it the higher performance motorcycles would ever requireTWO per tire?
Put another way, if a Honda CBR1000RR needs two brake rotors per tire for effective stopping then by your logica 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...
ORIGINAL: CrazyAl
Brembo is trying to sell you something, of course!!
Brembo is trying to sell you something, of course!!
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 makesSOME 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 doesANY motorcycle have two rotors up front? If a car, which you argue has a heavier load on each disc brake, can get by with onlyONE rotor per tire, then why is it the higher performance motorcycles would ever requireTWO per tire?
Put another way, if a Honda CBR1000RR needs two brake rotors per tire for effective stopping then by your logica 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...