View Poll Results: Brake Discs: Drilled, Slotted, Both, or Neither?
Drilled
23
10.09%
Slotted
89
39.04%
Both
84
36.84%
Neither
32
14.04%
Voters: 228. You may not vote on this poll
Brake Discs: Drilled, Slotted, Both, or Neither?
Originally Posted by StopTech
You guys are going way overboard on some of these statements.
First off, on a street only car, any rotor finish will be fine. If you really like the look of drilled, go for it if it makes you happy. Will the pads wear a little quicker? Yes, but not so much that you will be changing them exsessively or even have to worry about it. In many cases, the increased pad volume of a BBK will mean that your pads will last much longer than stock no matter what rotor finish you choose.
If you are tracking your car, go with slotted. They will hold up much better to high temps and will be more resistant to cracking than the drilled. A properly slotted rotor that does not have the slot going out to the outer edge and has tapered slots will last nearly as long as a plain rotor with regards to cracking. Again, slotted rotors will increasse pad wear to a degree but it is really not something that is significant to worry about.
For the record, NONE of our race teams use blank rotors. We are talking about race and championship winning production based cars in World Challenge TC and GT and Grand Am cup Koni Challenge. Many of these teams will only use 2 sets of rotors in an entire season which includes all of their practice and testing. The TriPoint Mazdas who have absolutely dominated World Challenge TC are running drilled rotors of all things (GASP!) and they are doing just fine. At the end of the day, the rotors are secondary to proper pad selection and adequate brake cooling when things start to get serious.
As to the statement about Porsche using cast holes, it has not been proven and Porsche engineers have even posted that they are drilled at the foundry. The ONLY reason porsche sells cars with drilled rotors is for appearance purposes and the race car look they offer.
First off, on a street only car, any rotor finish will be fine. If you really like the look of drilled, go for it if it makes you happy. Will the pads wear a little quicker? Yes, but not so much that you will be changing them exsessively or even have to worry about it. In many cases, the increased pad volume of a BBK will mean that your pads will last much longer than stock no matter what rotor finish you choose.
If you are tracking your car, go with slotted. They will hold up much better to high temps and will be more resistant to cracking than the drilled. A properly slotted rotor that does not have the slot going out to the outer edge and has tapered slots will last nearly as long as a plain rotor with regards to cracking. Again, slotted rotors will increasse pad wear to a degree but it is really not something that is significant to worry about.
For the record, NONE of our race teams use blank rotors. We are talking about race and championship winning production based cars in World Challenge TC and GT and Grand Am cup Koni Challenge. Many of these teams will only use 2 sets of rotors in an entire season which includes all of their practice and testing. The TriPoint Mazdas who have absolutely dominated World Challenge TC are running drilled rotors of all things (GASP!) and they are doing just fine. At the end of the day, the rotors are secondary to proper pad selection and adequate brake cooling when things start to get serious.
As to the statement about Porsche using cast holes, it has not been proven and Porsche engineers have even posted that they are drilled at the foundry. The ONLY reason porsche sells cars with drilled rotors is for appearance purposes and the race car look they offer.
Originally Posted by push
You aren't generating more torque, torque is created by the caliper. As long as you can lock them up you have enough brake torque, any more will just add that much more pressure to the rotor, but wont aid stopping distance. You would have more pad on rotor surface area, but not much. Slotting only takes around 4% of the rotor and the slots create friction, so it should have more 'bite'. I'm sure with identical setups with one having slotted and the other blanks, you will not notice much if any difference at all. The key to better braking is suspension, tires and being able to keep your brakes cool.
Again, mechanical friction isn't at work while braking. It an adhesive friction mode (might not be the proper name).
Considering that my Brembo + track pad setup on RA1 tires can generate in excess of 1,300hp of braking power and that this is still not enough to lock up the wheels, the 4% torque difference (~50hp) is pretty significant...
On the street, you're right, nobody will fell that difference. Except when it's time to change pads earlier (slots) or when the rotors are cracked (drilled). Or, like many people seem to care, when it's time to clean your wheels...
Nobody is in danger by choosing either type of rotors. Most guys here are looking at ways to reduce the weight of their car or to gain 2% power with a nice CAI in the name of increased performance, but they won't get the slightly better (and cheaper) brake setup...
Last edited by Kolia; Jun 20, 2007 at 11:56 AM.
Originally Posted by Kolia
Again, mechanical friction isn't at work while braking. It an adhesive friction mode (might not be the proper name).
Considering that my Brembo + track pad setup on RA1 tires can generate in excess of 1,300hp of braking power and that this is still not enough to lock up the wheels, the 4% torque difference (~50hp) is pretty significant...
On the street, you're right, nobody will fell that difference. Except when it's time to change pads earlier (slots) or when the rotors are cracked (drilled). Or, like many people seem to care, when it's time to clean your wheels...
Nobody is in danger by choosing either type of rotors. Most guys here are looking at ways to reduce the weight of their car or to gain 2% power with a nice CAI in the name of increased performance, but they won't get the slightly better (and cheaper) brake setup...
Considering that my Brembo + track pad setup on RA1 tires can generate in excess of 1,300hp of braking power and that this is still not enough to lock up the wheels, the 4% torque difference (~50hp) is pretty significant...
On the street, you're right, nobody will fell that difference. Except when it's time to change pads earlier (slots) or when the rotors are cracked (drilled). Or, like many people seem to care, when it's time to clean your wheels...
Nobody is in danger by choosing either type of rotors. Most guys here are looking at ways to reduce the weight of their car or to gain 2% power with a nice CAI in the name of increased performance, but they won't get the slightly better (and cheaper) brake setup...
Brake torque is essentially the power of the braking system. The brake caliper acts on the disc at a certain distance from the hub center, known as the effective radius. The force exerted by the caliper, multiplied by the effective radius of the system equals the brake torque. Increasing either the force applied by the caliper, or the effective radius results in increased brake torque.
The fact that it leaves you with 4% less usable rotor material I believe is made up with the fact you are adding more friction from the grooves, and have a continually new (flat) pad surface. Stoptech already said that all of their cars are running slotted rotors, not blanks. If blanks were the end all be all of rotors, I'm sure they would be using them. Everywhere I have read, and the people I talk to (who track) recommend a slotted rotor for the track because of what I mentioned above. In the end it's not going to be a night and day difference between slotted/blank when you talk about a good brake setup. Like StopTech said it comes down to picking a good pad and having a good BBK that can keep heat manageable. Until I see/hear/experience otherwise I think slotted rotors have more to offer than blanks.
Last edited by push; Jun 20, 2007 at 01:18 PM.
Slotted, drilled or dimpled rotors offered as OEM replacements should not be considered appropriate for high-speed track use.
While grooved, drilled and slotted rotors offer an enhanced appearance and add some resistance to the boundary layer of gasses that can build up between the pad and rotor, they are not designed to withstand the extreme temperatures that are produced on the racetrack. If they are used on the track, it is very important that the rotors be carefully inspected and should not be driven on if even minor signs of deterioration are seen. Note, too, that if these products are used on the track they are not warrantable.
Reference: http://www.tirerack.com/brakes/tech/....jsp?techid=87
While grooved, drilled and slotted rotors offer an enhanced appearance and add some resistance to the boundary layer of gasses that can build up between the pad and rotor, they are not designed to withstand the extreme temperatures that are produced on the racetrack. If they are used on the track, it is very important that the rotors be carefully inspected and should not be driven on if even minor signs of deterioration are seen. Note, too, that if these products are used on the track they are not warrantable.
Reference: http://www.tirerack.com/brakes/tech/....jsp?techid=87
Originally Posted by davidv
Slotted, drilled or dimpled rotors offered as OEM replacements should not be considered appropriate for high-speed track use.
While grooved, drilled and slotted rotors offer an enhanced appearance and add some resistance to the boundary layer of gasses that can build up between the pad and rotor, they are not designed to withstand the extreme temperatures that are produced on the racetrack. If they are used on the track, it is very important that the rotors be carefully inspected and should not be driven on if even minor signs of deterioration are seen. Note, too, that if these products are used on the track they are not warrantable.
Reference: http://www.tirerack.com/brakes/tech/....jsp?techid=87
While grooved, drilled and slotted rotors offer an enhanced appearance and add some resistance to the boundary layer of gasses that can build up between the pad and rotor, they are not designed to withstand the extreme temperatures that are produced on the racetrack. If they are used on the track, it is very important that the rotors be carefully inspected and should not be driven on if even minor signs of deterioration are seen. Note, too, that if these products are used on the track they are not warrantable.
Reference: http://www.tirerack.com/brakes/tech/....jsp?techid=87
the fact is, that look at the paddoc at any major competition, and you'll find either slotted or drilled rotors on, I would venture to say, the overwhelming majority of cars
Originally Posted by push
What is brake torque?
Brake torque is essentially the power of the braking system. The brake caliper acts on the disc at a certain distance from the hub center, known as the effective radius. The force exerted by the caliper, multiplied by the effective radius of the system equals the brake torque. Increasing either the force applied by the caliper, or the effective radius results in increased brake torque.
The fact that it leaves you with 4% less usable rotor material I believe is made up with the fact you are adding more friction from the grooves, and have a continually new (flat) pad surface. Stoptech already said that all of their cars are running slotted rotors, not blanks. If blanks were the end all be all of rotors, I'm sure they would be using them. Everywhere I have read, and the people I talk to (who track) recommend a slotted rotor for the track because of what I mentioned above. In the end it's not going to be a night and day difference between slotted/blank when you talk about a good brake setup. Like StopTech said it comes down to picking a good pad and having a good BBK that can keep heat manageable. Until I see/hear/experience otherwise I think slotted rotors have more to offer than blanks.
Brake torque is essentially the power of the braking system. The brake caliper acts on the disc at a certain distance from the hub center, known as the effective radius. The force exerted by the caliper, multiplied by the effective radius of the system equals the brake torque. Increasing either the force applied by the caliper, or the effective radius results in increased brake torque.
The fact that it leaves you with 4% less usable rotor material I believe is made up with the fact you are adding more friction from the grooves, and have a continually new (flat) pad surface. Stoptech already said that all of their cars are running slotted rotors, not blanks. If blanks were the end all be all of rotors, I'm sure they would be using them. Everywhere I have read, and the people I talk to (who track) recommend a slotted rotor for the track because of what I mentioned above. In the end it's not going to be a night and day difference between slotted/blank when you talk about a good brake setup. Like StopTech said it comes down to picking a good pad and having a good BBK that can keep heat manageable. Until I see/hear/experience otherwise I think slotted rotors have more to offer than blanks.
Force is only one part of the equation. The other being, surface area and the infamous coefficient of friction (mu!). Slots = less surface. Clean pads surface? What's to remove? You're slicing throught an homogenious material!!!
My source for chosing plain above all ? I've worked 2 years at Ferrari F1, wind tunnel testing. A good friend of mine is a material engineer there. When I was faced with a blown drilled/slotted rotors and showed it to him, I got treated to a rather long lecture on chosing my next setup wisely...
Now, I don't want to start a debate between StopTech and the Scudderia Ferrari. I actually run StopTech (plain) 2 pieces rotros on my Z.
To each his own, I run plain rotors...
Last edited by Kolia; Jun 20, 2007 at 01:44 PM.
Vendor - Former Vendor
Joined: Aug 2005
Posts: 333
Likes: 1
From: Compton, CA
The iron composition can have a lot to do with the crack resistance. Most one peice OE replacement rotors and even OE parts dont have iron that can hold up like high end BBK rotors. With most OE replacements like what TireRack sells, the lower quality iron used (when compared to BBK parts) wont hold up to aggressive track use, especially when slots or drilled or added, hence the warning.
Even among BBK manufacturers there are varying levels of crack resistance based on Iron formulation. With our 2 peice rotors on your car Kolia, you could gain a little bit of bite with our slotted parts without having to worry about premature rotor failure.
Even among BBK manufacturers there are varying levels of crack resistance based on Iron formulation. With our 2 peice rotors on your car Kolia, you could gain a little bit of bite with our slotted parts without having to worry about premature rotor failure.
Thanks, I already have plenty of bite running the Cobalt Friction carbon/ceramic pads. It's actually touchy to get my aging tires warm enough to cope with it. The pads might last 6 track days if I'm lucky.
And the rotors aren't far behind at that. I doub't they'll make it through a second set of pads. Driving the pads on the street probably didn't help them... (oups!)
I need cooling ducts bad...
And the rotors aren't far behind at that. I doub't they'll make it through a second set of pads. Driving the pads on the street probably didn't help them... (oups!)
I need cooling ducts bad...
not to add fuel to the fire, but there are more than a few Ferraris that run non solid rotors, both past and present
if the solids work for you, that's cool - but they are not the be all and end all solution, rather, just a different path
if the solids work for you, that's cool - but they are not the be all and end all solution, rather, just a different path
Lol, I'm very much alone on my side here ! 
And I'm loosing my poll "election"!
I totally agree.
But who knows the exact reasons behind the selection of a brake system for a company that builds high performance and aestheticaly pleasin exotic cars?
I don't.
The only thing I know is what I've posted earlier. I don't need slots or holes for my application. I have no pad fade at the track and don't lack in initial bite. My brakes don't last that long at the track, yet I still have the original pads on for the street (40k miles).
That's the setup that works for me and that was recommanded by someone I trust knows his stuff. So in turn I recommand it to others.
Holes just crack after a few spirited runs. But slot might still be an option.
At the end of the day, each must decide for himself what will govern his choice. Aesthetics? Performance? Application? Is there an issue we are trying to address ? Are we experiencing pad fade but aren't willing to get different pads to mount and dismount each time? Then yes, maybe slots could help extend the pads' endurance and fade resistance.
Is brake dust an issue ? I'd say avoid slots and holes if it is!
Nice topic
And I'm loosing my poll "election"!
Originally Posted by Z1 Performance
not to add fuel to the fire, but there are more than a few Ferraris that run non solid rotors, both past and present
if the solids work for you, that's cool - but they are not the be all and end all solution, rather, just a different path
if the solids work for you, that's cool - but they are not the be all and end all solution, rather, just a different path
But who knows the exact reasons behind the selection of a brake system for a company that builds high performance and aestheticaly pleasin exotic cars?
I don't.
The only thing I know is what I've posted earlier. I don't need slots or holes for my application. I have no pad fade at the track and don't lack in initial bite. My brakes don't last that long at the track, yet I still have the original pads on for the street (40k miles).
That's the setup that works for me and that was recommanded by someone I trust knows his stuff. So in turn I recommand it to others.
Holes just crack after a few spirited runs. But slot might still be an option.
At the end of the day, each must decide for himself what will govern his choice. Aesthetics? Performance? Application? Is there an issue we are trying to address ? Are we experiencing pad fade but aren't willing to get different pads to mount and dismount each time? Then yes, maybe slots could help extend the pads' endurance and fade resistance.
Is brake dust an issue ? I'd say avoid slots and holes if it is!
Nice topic
A person I know who has been going to track days for 7 years now, about 5-6 per year recommended that I stick with blank rotors and a good quality pad. So, like Kolia, I'm taking that advice, and so far I haven't had MUCH trouble. But, I'm only using a street/track pad, HP+, not a dedicated track pad. I'm convinced that if I step up my pad choice then I won't have any trouble on the track, and I'm using BASE brakes as well.
Originally Posted by Kolia
What happened to the good 'ole friction equation ?!?
Force is only one part of the equation. The other being, surface area and the infamous coefficient of friction (mu!). Slots = less surface. Clean pads surface? What's to remove? You're slicing throught an homogenious material!!!
Force is only one part of the equation. The other being, surface area and the infamous coefficient of friction (mu!). Slots = less surface. Clean pads surface? What's to remove? You're slicing throught an homogenious material!!!
Originally Posted by push
You would then know that the slot adds a source of friction itself. It's easier to stop something with groves in it than a flat, smooth surface.
But in the specific case of a brake pad working in it's operating range of temperature, (That's the 3rd time I'm say that in this topic I think), the friction is generated via an exchange of electrons. You need contact for these littles guys to be ripped from their atoms...
This is probably a reason why slots are said to help with initial bite. They grind the pad during the fraction of a second it takes for it to reach working temps and to then stick to the rotor.
No, for maximum torque while braking, you can't beat a plain rotor.
Oh, try braking on rumbble strips and let us know if it help the car slow down... ABS comes on immidiately then? I wonder why...
Last edited by Kolia; Jun 21, 2007 at 04:43 AM.
Originally Posted by Kolia
Lol, I'm very much alone on my side here !
And I'm loosing my poll "election"!
I totally agree.
But who knows the exact reasons behind the selection of a brake system for a company that builds high performance and aestheticaly pleasin exotic cars?
I don't.
The only thing I know is what I've posted earlier. I don't need slots or holes for my application. I have no pad fade at the track and don't lack in initial bite. My brakes don't last that long at the track, yet I still have the original pads on for the street (40k miles).
That's the setup that works for me and that was recommanded by someone I trust knows his stuff. So in turn I recommand it to others.
Holes just crack after a few spirited runs. But slot might still be an option.
At the end of the day, each must decide for himself what will govern his choice. Aesthetics? Performance? Application? Is there an issue we are trying to address ? Are we experiencing pad fade but aren't willing to get different pads to mount and dismount each time? Then yes, maybe slots could help extend the pads' endurance and fade resistance.
Is brake dust an issue ? I'd say avoid slots and holes if it is!
Nice topic
And I'm loosing my poll "election"!
I totally agree.
But who knows the exact reasons behind the selection of a brake system for a company that builds high performance and aestheticaly pleasin exotic cars?
I don't.
The only thing I know is what I've posted earlier. I don't need slots or holes for my application. I have no pad fade at the track and don't lack in initial bite. My brakes don't last that long at the track, yet I still have the original pads on for the street (40k miles).
That's the setup that works for me and that was recommanded by someone I trust knows his stuff. So in turn I recommand it to others.
Holes just crack after a few spirited runs. But slot might still be an option.
At the end of the day, each must decide for himself what will govern his choice. Aesthetics? Performance? Application? Is there an issue we are trying to address ? Are we experiencing pad fade but aren't willing to get different pads to mount and dismount each time? Then yes, maybe slots could help extend the pads' endurance and fade resistance.
Is brake dust an issue ? I'd say avoid slots and holes if it is!
Nice topic
Regarding what Ferari et. al choose to do, it was you who mentioned them, not me. They not only run these types of rotors on their street cars they also run them on countless track cars too, ranging from your "run of the mill" Challenge cars, up to the LeMans class cars (I've spent considerable time with them, and have seen these first hand for years). These are what I was referring to...not their street machines. So is this for aesthetic reasons too?
Again, if it works for you, great - but to go so far as to say that your way is right and the others are wrong, when there are plenty involved in far more competitive racing than you are (or I am) running other solutions not only effectively, but with outstanding results, is short sighted.
Last edited by Z1 Performance; Jun 21, 2007 at 07:32 AM.
Registered User
Joined: May 2007
Posts: 930
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From: Richmond, VA
You know what I just thought about.....my streetbike, and pretty much all motorcycles have drilled (or holed) rotors. and I know the braking on a bike is more intense than a car.
Any perspective on this?
Any perspective on this?
Kolia - dude, you're off base on several of your posts. I liked your statement about "electron transfer" - lol!
First the appropriate terms are the coefficient of static friction and the coefficient of kinetic friction. The former is higher than the later and they refer to two mating surfaces either at rest or moving respectively. Second the frictional force is going to equal the coefficient * the clamping force.
Now the clamping force does not change w/ a change in rotors. The coefficient of friction is going to be affected by available contact surface area, but as mentioned above, the surface area drop w/ slots or drilling is minimal. More significantly as the rotor becomes "glazed" from heat, the coefficient of friction (both static and kinetic) drop. The slotted rotors help prevent this drop.
Anyway, my idea for a more useful rotor design is actually to use more of a fan design with thin slots (fully drilled but at an extreme oblique angle, not just shallow grooves) where the drilled out slots communicate with the inner cooling vanes. The theory being it will actually pull air in from outside of the rotor (like a fan). Hey stoptech dudes, if you prototype this after reading it, send me a free set would 'ya? (if it worked that is - lol)
First the appropriate terms are the coefficient of static friction and the coefficient of kinetic friction. The former is higher than the later and they refer to two mating surfaces either at rest or moving respectively. Second the frictional force is going to equal the coefficient * the clamping force.
Now the clamping force does not change w/ a change in rotors. The coefficient of friction is going to be affected by available contact surface area, but as mentioned above, the surface area drop w/ slots or drilling is minimal. More significantly as the rotor becomes "glazed" from heat, the coefficient of friction (both static and kinetic) drop. The slotted rotors help prevent this drop.
Anyway, my idea for a more useful rotor design is actually to use more of a fan design with thin slots (fully drilled but at an extreme oblique angle, not just shallow grooves) where the drilled out slots communicate with the inner cooling vanes. The theory being it will actually pull air in from outside of the rotor (like a fan). Hey stoptech dudes, if you prototype this after reading it, send me a free set would 'ya? (if it worked that is - lol)
The fact that I don't agree doesn't mean we have to get aggressive.
If you read my posts again, you'll see that I left the door open to different applications. Why are you guys reacting so strongly? I'm one voice amongst a whole topic, yet you somehow feel threatened by my comments? Where are the brake gurus to turn my ideas upside down? Q45? SpacemanSpiff?
F1 cars run solid carbon-carbon rotors. Yet I haven't used that argument. Why? Simply because FIA regulation forces the teams to use that type of rotors. What is used in racing isn't always the best way to go for a street car. Our friend StopTech said that Koni Challenge teams and others, run slotted rotors that last half a season or more. That's great. I'm assuming these team's pads don't last that long... Probably more like a fresh set of pads every races...
Now. I don't mind the attacks really. I'm confident that my statements are true and I'm just waiting for a proper technical argument against any of them.
Comparing a BBK with larger rotors, and different pads to the OEM setup to back up a claim that slotted rotors don't generate more dust than plain? Come on... Apple and oranges...
And everybody agrees that slots help to clean the pad and refreshes the surface, but again won't generate dust... Nobody ever sanded a wood plank here?
Not knowing what happens when matter if forced unto matter isn't a sin either. Until I read about the subject, I had no idea of what was happening at the atomic level when grip/friction is generated. The electron exchange thing happens all the time. From rubbing a balloon to your head to make it stick to the wall, to your tires on the pavement and the pads on your rotor.
Damn, I haven't been to school very long. The electron thing was hinted at while I was in high school!
I've said what I had to say. I've even stated my sources.
If you read my posts again, you'll see that I left the door open to different applications. Why are you guys reacting so strongly? I'm one voice amongst a whole topic, yet you somehow feel threatened by my comments? Where are the brake gurus to turn my ideas upside down? Q45? SpacemanSpiff?
F1 cars run solid carbon-carbon rotors. Yet I haven't used that argument. Why? Simply because FIA regulation forces the teams to use that type of rotors. What is used in racing isn't always the best way to go for a street car. Our friend StopTech said that Koni Challenge teams and others, run slotted rotors that last half a season or more. That's great. I'm assuming these team's pads don't last that long... Probably more like a fresh set of pads every races...
Now. I don't mind the attacks really. I'm confident that my statements are true and I'm just waiting for a proper technical argument against any of them.
Comparing a BBK with larger rotors, and different pads to the OEM setup to back up a claim that slotted rotors don't generate more dust than plain? Come on... Apple and oranges...
And everybody agrees that slots help to clean the pad and refreshes the surface, but again won't generate dust... Nobody ever sanded a wood plank here?
Not knowing what happens when matter if forced unto matter isn't a sin either. Until I read about the subject, I had no idea of what was happening at the atomic level when grip/friction is generated. The electron exchange thing happens all the time. From rubbing a balloon to your head to make it stick to the wall, to your tires on the pavement and the pads on your rotor.
Damn, I haven't been to school very long. The electron thing was hinted at while I was in high school!
I've said what I had to say. I've even stated my sources.
Last edited by Kolia; Jun 21, 2007 at 06:19 AM.
People seem to respond better when links are being posted.
Here's a good one from a reputable brake manufacturer about the nature of friction.
http://www.stoptech.com/tech_info/wp_bedintheory.shtml
Pay attention to the abrasive and adhesive friction description...
Here's a good one from a reputable brake manufacturer about the nature of friction.
http://www.stoptech.com/tech_info/wp_bedintheory.shtml
Pay attention to the abrasive and adhesive friction description...