Curious to see what cross-drilled rotors look like pair with OEM Brembos. I've seen slotted-only, and cross-drilled + slotted, but not cross-drilled only. Please post pix if you have any.

 

Why? Blanks are best!!

 

^ Len, have you ever used both and temp gun'd them after laps?

-J

 

You kidding? They don't dissipate heat as well as slotted do they? Maybe cheapest i'd imagine.

 

IMHO,

Holes are drilled in rotors to reduce the weight of the rotor and thus reduce unsprung mass. In all of my testing with IR temp guns and temp paint, checking the temps of the rotors AND calipers, there's no significant difference in total heat between cross drilled, slotted, and flat rotors. Holes in rotors do nothing measurable for brake for cooling. Granted, that testing is almost next to meaningless but, without mounted in place temp probes and data collection its the best we can do.

 

What about integrity of drilled rotors? Aren't they prone to cracking vs slotted

 

No difference for a street driven car. On a race car they tend to crack a little sooner then flat rotors, but all rotors crack over time when used on a race track.

 

blanks are better, the cooling of the rotor is done thru the "fins" you see in between the 2 surfaces. the reason why drilled and slotted are around is because back in the day brake pads produced a gas under high heat witch was prone to cause a "bubble" between the pad and the rotor. the holes and slots where meant to dissipate the gas not heat. nowadays pads no loner have that problem, so buying those rotors is purely cosmetic. the reason i say blanks are better is because there is more contact surface area with pad and rotor, getting drilled and slotted removes from that surface area.

 

++1

 

Forgot about this thread. I know the slotted vs. drilled vs. blanks is always a topic folks have differing opinions on. So thanks all for the insight and discussion!

As for pix, I found a few on the net, in case anybody was curious (Brembo Sport Cross Drilled Rotors):

 

Drilled rotors provide more initial bite, especially at higher speeds. This has been demonstrated repeatedly by many, including myself, using data acquisition and feedback from professional drivers. If you ever get the chance to test them back to back on the same car, same tires, same pads (properly bedded on both sets of rotors), you will surely feel the difference within half a second of stepping on the brake pedal. The faster you go, the more difference they make.

The reason for the extra bite is the extra leading edges that the holes provide, just like when we used to cut extra slots in brake pads with hacksaws back in the day. Of course, the extra holes (and/or slots) do increase pad wear, but that is because they are making the pad work harder!

That said, drilled rotors are not ideal for hard track use. I have used them for qualifying before -- but make DARN SURE you tell the driver you've switched them back BEFORE he goes out for the morning warm up (unless your crew is up for some panic repairs before the race starts).

For racing, the pros use J-Hook<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->™ rotors as they provide the extra bite that cross-drilled rotors do without the stress risers. If you are going to the track and J-Hooks<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]-->™ are not available, slotted-only rotors are the next best choice. But for the street, autocross and non-competitive HPDE events, good quality drilled rotors will last nearly as long as plain-face rotors. If you buy junk instead, well, you'll often get what you pay for.

Chris

 

That is completely true.

Back in the 90's, there were a lot of internet discussions about cross drilled and slotted rotors providing excellent initial bite compared to blank rotors. At the time, nobody really knew why. People were suspecting that the holes and slots were providing extra cooling, therefore better initial bite.

I said the same thing you said about how the edges provide more bite, based on my own experience and observation. I was harassed and received numerous internet death threats from the blank rotor ***** for making such comment.

Someone's gotta get the truth out!!!

 

Well, there are truths and there are Internet forums. Every now and then the two meet.

It's funny how people will take many things they read seriously without first qualifying the source. Not all experts agree all the time, but there are people with significant experience in areas that other people with less experience will spend significant time and energy arguing about. I guess that's just the way it is.

I'm not an expert in equity trading, but I have read some articles on the topic. However, you won't find me boldly posting my opinions on the trading forums as if I know what I'm talking about. I may post some questions if I can work out that there are some actual experts willing to spend time on the boards to share. Otherwise, I would just be wasting my time and, potentially, my money. I would be much better off paying an expert a little bit and making money than relying on conjecture and poorly-formed opinion just to lose much more.

And don't worry much about the death threats. Those guys would have to actually find clean underwear, put pants on and leave their grandmother's basement to get after you. Not likely to happen!

 

I don't know either way, my quesiton is more fundamental. Is more initial bite a good or bad thing?

In all cases it depends on the car, setup, driver, and conditions.

How much grip is generated through aero?
What's that downforce balance?
Do you want more bite in back or in front of the car - at high speed, at medium speed, at low speed?
Is your driver a leadfoot or a featherfoot braker?
Can the tires handle a hard initial bite without lockup (lightweight Hoosier bias slicks or big heavy 22" Fuzions)?
Is there a balance bar in the braking system or just a prop valve?
How much does the car weigh?
What's ramp up on the bite of the pad material itself?
Is it better to tune initial bite with rotor or pad material?
Is it going to be a wet, damp, or dry track?
Do you drive in Seatle or Phoenix?

And Internet Death Threats? Really?

 

Aero? Balance bar? Really??? This is an enthusiast 350Z forum. I seriously doubt any regular posters here are paying to have their cars tested in a full-sized, rolling road wind tunnel or have linear pots on their cars to measure suspension compression at 80, 120, 160 and 200 mph to graph aero loads. And balance bars are often installed and adjusted incorrectly by anyone but the most serious racers who have experience with them. Regardless, high initial bite is a great thing IF you are not grip limited, i.e., you have enough tire traction available to be able take advantage of it. It's a bad thing if the brake balance is screwed up and tires start to lock up easily. Many of the drivers I've worked with in high-downforce cars (5,000 to 14,000+ lbs.) could not get enough bite to lock up the tires at 200 mph even if practically standing on the brake pedal. But they were also braking at over 4g's already!

We're pretty far off-topic anyway, as I believe the OP was mainly interested in how cross-drilled rotors looked with the OE Track Model Brembos.

 

That's the beauty of the Internet.

 

IMO, rotors that are built then drilled have lost build integrity. I believe Porche is one of the few that actually manufactures holes in their rotors as opposed to drilling them at the end product. You didn't specify why you're interested in cross-drilled so I'm assuming it's for looks. If that's the case then save yourself the cash and keep your rotors until YOU NEED new rotors not just because YOU WANT new rotors.

 

Um, no. Porsche does not. They are actually made mostly (but not all) by Brembo anyway. The holes are drilled. This in an Internet myth that refuses to die for some unknown reason.

Chris

 

I got my drilled rotors mostly cause of the cosmetic aspect plus they are a lot cheaper than OEM rotors for the brembo package $580.00 for the rotors and $250.00 for the pads at the stealership? No thanks.

 

You sound like the right crusader to ensure it's demise.