Advantages to slotted or drilled rotors? I don't think so.

DannyGT · 08-14-2009, 08:27 PM

Just curious, but do the holes make a difference on ceramics? Why would Porsche use a cross drilled setup on the 911 GT2?

JoeD · 08-14-2009, 08:42 PM

Quote:

Originally Posted by DannyGT

Just curious, but do the holes make a difference on ceramics?

The difference, per se, is no different if it's a ceramic or non-ceramic rotor. In other words...the holes are equally as useless in both applications.

Quote:

Originally Posted by DannyGT

Why would Porsche use a cross drilled setup on the 911 GT2?

Because that's what Brembo supplied them with. As well as Ferrari, Aston Martin, Bugatti, Lamborghini, Chevrolet, Bentley, Pagani, Mercedes-Benz, etc.

Cjanik · 08-15-2009, 01:41 AM

^^ besides the theory of hype, your, and the OP's, suggestions of that they are useless doesn't go anywhere.

you are both saying that no proof of benefits = hype, well then show us proof that it doesn't work and its function is hype. the burden of proof is on you and you have not delivered.

I can name half a dozen reasons why its better to have cross drilled, just as you can name half a dozen reasons why its better not to have them, so dont bother with that - go for the testing thats been done and show the results.

-edit- wanted to mention, a well known fact of drilled or slotted rotors is the holes allow the gases and dirt to pass through the hole, versus piling up between the pad and the rotor acting like ball bearings, this allows a much better "bite". I wanted to point this out because you said it gives less grip due to less surface area. The same goes with heating, less mass for heat dissipation? where's the heat going to go if there's no air/gas moving through transfering the heat? thats where the holes come into play - more air movement = less heat. You dont need rotors to prove that, look at any part that creates heat and how it removes the heat.

JoeD · 08-15-2009, 06:01 AM

Quote:

Originally Posted by Cjanik

^^ besides the theory of hype, your, and the OP's, suggestions of that they are useless doesn't go anywhere.

you are both saying that no proof of benefits = hype, well then show us proof that it doesn't work and its function is hype. the burden of proof is on you and you have not delivered.

I can name half a dozen reasons why its better to have cross drilled, just as you can name half a dozen reasons why its better not to have them, so dont bother with that - go for the testing thats been done and show the results.

-edit- wanted to mention, a well known fact of drilled or slotted rotors is the holes allow the gases and dirt to pass through the hole, versus piling up between the pad and the rotor acting like ball bearings, this allows a much better "bite". I wanted to point this out because you said it gives less grip due to less surface area. The same goes with heating, less mass for heat dissipation? where's the heat going to go if there's no air/gas moving through transfering the heat? thats where the holes come into play - more air movement = less heat. You dont need rotors to prove that, look at any part that creates heat and how it removes the heat.

LOL.

I'll quote GRM:

"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)"

Please read, mainly the entire first post if anything. Some good info.

The real deal about cross-drilled and Slotted Rotors - IWSTI.com: Subaru WRX STI Forums

After that, dig around on the websites of manufacturers of brakes and see what they have to say about drilled vs. slotted rotors. Remember, it's in their financial interest not to talk down on essentially half their products, but there comes a point where you just cannot lie. When you're done doing that, take a peek behind the wheels of a Formula 1 or Le Mans car.

Do I speak from first-hand experience as to which one is better? No. All the cars I have driven on a track competitively or in HPDEs have had conventional and/or slotted rotors so I cannot compare. Does that make my opinion moot, though? Hardly. Doing so would be along the lines of dismissing someone's opinion that an eBay electronic supercharger or "Tornado" does not provide gains simply because they haven’t tried it.

And for the record, the burden-of-proof always lies on the party making the claim of an advantageous development or idea, not the inverse. Now show me a manufacturer, racing-team, or seasoned road-racing enthusiast who has come out in favor of drilled rotors.

Snakebite202 · 08-15-2009, 10:51 AM

NASCAR does use slotted rotors as well as a lot of the GT cars, DP cars, and a ton of other classes/series which I think the above post makes mention of the cars in NASCAR.

I guess what I'm saying is the that the better argument is wether or not drilled rotors have any use since slotted rotors seem to have already proven their usefulness. Also most teams running carbon-carbon set ups don't use any slots.

Cjanik · 08-15-2009, 11:58 AM

Quote:

Originally Posted by JoeD

LOL.

I'll quote GRM:

"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)"

Please read, mainly the entire first post if anything. Some good info.

The real deal about cross-drilled and Slotted Rotors - IWSTI.com: Subaru WRX STI Forums

After that, dig around on the websites of manufacturers of brakes and see what they have to say about drilled vs. slotted rotors. Remember, it's in their financial interest not to talk down on essentially half their products, but there comes a point where you just cannot lie. When you're done doing that, take a peek behind the wheels of a Formula 1 or Le Mans car.

Do I speak from first-hand experience as to which one is better? No. All the cars I have driven on a track competitively or in HPDEs have had conventional and/or slotted rotors so I cannot compare. Does that make my opinion moot, though? Hardly. Doing so would be along the lines of dismissing someone's opinion that an eBay electronic supercharger or "Tornado" does not provide gains simply because they haven’t tried it.

And for the record, the burden-of-proof always lies on the party making the claim of an advantageous development or idea, not the inverse. Now show me a manufacturer, racing-team, or seasoned road-racing enthusiast who has come out in favor of drilled rotors.

why the "LOL"?

anyhow, looked into it, I think got me.

kdoske · 08-15-2009, 12:12 PM

They were useful when asbestos pads were still made. Besides that who cares. If you have the money and you can afford them, get em, they look cool as hell.

imag · 11-18-2009, 03:09 PM

I am wondering if AP- Chris and/or Gary could weigh in on this, as it's something I have always wondered. A friend of mine from Wilwood said that cross drilled rotors are a bad idea for anyone except a racing team, where they really need the weight savings and can afford to replace rotors after every race.

It certainly seems true that low-end cross drilled rotors crack. That said, top-line Porsches (GT3, etc.) and others have cross drilled brakes and they seem to do okay at the track.

Can you guys settle this once and for all? Looks aside, when does it make sense to go cross drilled, if ever?

ChrisSlicks · 11-18-2009, 03:23 PM

All rotors crack under track conditions eventually, especially if there is insufficient cooling to rotor. You have to look for the tell tale signs around the edge of the rotors to see the beginnings of cracks starting. I've seen non-slotted rotors crack all the way through where someone ignored those signs. The issue with cross-drilled is that the crack tends to play "connect the dots" and can turn from a minor check to a major crack fairly quickly, the stock Corvette Z06 has this issue.

You are correct that many race teams use them for the added bite, but they are also running massive brake ducts so they can maintain temperatures in their target range, and like you said replace/rebuild on a regular basis.

I wouldn't run them myself, they just don't hold up as long at the track.

imag · 11-18-2009, 09:13 PM

I hear you Chris. I am wondering if the brake company folks can't comment because their companies sell both product types...

SmoothZ · 11-18-2009, 09:17 PM

The official brake rotors debate - NISSAN Z FORUM

My opinion means nothing, but I'm going to give it. For racing applications, cross-drilled or slotted rotors are used for a reason. I'm sure the teams have done tons of R&D, but I think part of the reason they run with them is from sponsorship demands.

Personally, I would get slotted over cross-drilled.

kannibul · 11-19-2009, 10:11 AM

Quote:

Originally Posted by M.J.

I totally agree with Hawk pads being a good first place to start if you are doing a simple brake upgrade. And like I said up there ^ much of what you say is good information. But you didn't personally test anything but standard style rotors, Hawk pads, and high temp fluid on your G. And magazine test articles are well, magazines. Road and Track tested the 370z base from 70mph n 161 feet. Then they recorded 163 feet from 70 with the sport brakes. We would still rather have the bigger brake package from the sport right? I think the thing is. I find it very difficult to accept the statement that there are no benefits to slotted or drilled rotors. I believe it's more of a cost to consumer issue for most manufactures. And okay, the aftermarket being what it is there is a Ton of hype on brake rotors. But still.
I'm just saying.

Interesting - 2ft longer stopping with the sport brakes? How is that possible? The only thing I can think of is higher weight in the rotors, wheels and tires...

ResIpsa · 11-19-2009, 01:35 PM

Check out the rotors on my old G35 after a day at Summit Point...

08-14-2009, 08:27 PM	#16 (permalink)
DannyGT Track Member Join Date: Jan 2009 Location: Jersey Posts: 919 Drives: 370Z (SOLD) Rep Power: 279	Just curious, but do the holes make a difference on ceramics? Why would Porsche use a cross drilled setup on the 911 GT2? __________________ Performance GTM Stage 1 SC, GTM Res.Test Pipes, Invidia Gemini Exhaust, GTM HD Oil Cooler Wheels & Suspension AME Tracer TM02's 19x9.5F 19x10.5R w/ 265x35F & 305x30R, Hotchkis Sways, BC (BR) Racing Coilovers (Car Sold)

08-15-2009, 01:41 AM	#18 (permalink)
Cjanik Track Member Join Date: May 2009 Location: Las Vegas Posts: 578 Drives: N/A Rep Power: 17	^^ besides the theory of hype, your, and the OP's, suggestions of that they are useless doesn't go anywhere. you are both saying that no proof of benefits = hype, well then show us proof that it doesn't work and its function is hype. the burden of proof is on you and you have not delivered. I can name half a dozen reasons why its better to have cross drilled, just as you can name half a dozen reasons why its better not to have them, so dont bother with that - go for the testing thats been done and show the results. -edit- wanted to mention, a well known fact of drilled or slotted rotors is the holes allow the gases and dirt to pass through the hole, versus piling up between the pad and the rotor acting like ball bearings, this allows a much better "bite". I wanted to point this out because you said it gives less grip due to less surface area. The same goes with heating, less mass for heat dissipation? where's the heat going to go if there's no air/gas moving through transfering the heat? thats where the holes come into play - more air movement = less heat. You dont need rotors to prove that, look at any part that creates heat and how it removes the heat. Last edited by Cjanik; 08-15-2009 at 01:53 AM.

08-15-2009, 10:51 AM	#20 (permalink)
Snakebite202 Base Member Join Date: Jun 2009 Location: Sumter, SC Posts: 182 Drives: Future 370z owner Rep Power: 428	NASCAR does use slotted rotors as well as a lot of the GT cars, DP cars, and a ton of other classes/series which I think the above post makes mention of the cars in NASCAR. I guess what I'm saying is the that the better argument is wether or not drilled rotors have any use since slotted rotors seem to have already proven their usefulness. Also most teams running carbon-carbon set ups don't use any slots. Last edited by Snakebite202; 08-15-2009 at 11:16 AM.

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08-15-2009, 12:12 PM	#22 (permalink)
kdoske Track Member Join Date: Jul 2009 Location: Louisiana Posts: 541 Drives: 800whp Unicorn FI Z Rep Power: 17	They were useful when asbestos pads were still made. Besides that who cares. If you have the money and you can afford them, get em, they look cool as hell.

11-18-2009, 03:09 PM	#23 (permalink)
imag Enthusiast Member Join Date: Mar 2009 Location: Oakland, CA Posts: 446 Drives: up the wall Rep Power: 16	I am wondering if AP- Chris and/or Gary could weigh in on this, as it's something I have always wondered. A friend of mine from Wilwood said that cross drilled rotors are a bad idea for anyone except a racing team, where they really need the weight savings and can afford to replace rotors after every race. It certainly seems true that low-end cross drilled rotors crack. That said, top-line Porsches (GT3, etc.) and others have cross drilled brakes and they seem to do okay at the track. Can you guys settle this once and for all? Looks aside, when does it make sense to go cross drilled, if ever?

11-18-2009, 03:23 PM	#24 (permalink)
ChrisSlicks A True Z Fanatic Join Date: Mar 2009 Location: North East Posts: 6,203 Drives: 09 370Z Sport M6 Rep Power: 653	All rotors crack under track conditions eventually, especially if there is insufficient cooling to rotor. You have to look for the tell tale signs around the edge of the rotors to see the beginnings of cracks starting. I've seen non-slotted rotors crack all the way through where someone ignored those signs. The issue with cross-drilled is that the crack tends to play "connect the dots" and can turn from a minor check to a major crack fairly quickly, the stock Corvette Z06 has this issue. You are correct that many race teams use them for the added bite, but they are also running massive brake ducts so they can maintain temperatures in their target range, and like you said replace/rebuild on a regular basis. I wouldn't run them myself, they just don't hold up as long at the track.

11-18-2009, 09:13 PM	#25 (permalink)
imag Enthusiast Member Join Date: Mar 2009 Location: Oakland, CA Posts: 446 Drives: up the wall Rep Power: 16	I hear you Chris. I am wondering if the brake company folks can't comment because their companies sell both product types...

11-18-2009, 09:17 PM	#26 (permalink)
SmoothZ A True Z Fanatic Join Date: Nov 2009 Location: Arrakis Posts: 7,952 Drives: giant sandworm Rep Power: 36	The official brake rotors debate - NISSAN Z FORUM My opinion means nothing, but I'm going to give it. For racing applications, cross-drilled or slotted rotors are used for a reason. I'm sure the teams have done tons of R&D, but I think part of the reason they run with them is from sponsorship demands. Personally, I would get slotted over cross-drilled.