Drilled Rotors worth it?

[nando]

I'd go with the ATE power disks, they're only a little more than stock rotors.

I've had mine on for over a year, done 4 autocrosses, some hard driving, and just general commuting. the pads probably do dust more, but I haven't worn through them yet. they also work great in the rain.

[modifiede30]

im about to redo my brakes so i have a few questions. from what i have gathered here, the best setup for an upgrade for just a daily driver would be oem rotors, SS lines, and better brake pads (probably gonna go with the mintex reds)? or should i get the ATE power discs for the front?

If all you're going to be driving is typical street speeds, and casual slow-downs, don't put racing pads on the car. Most racing pads are meant to operate at specific temperatures. Some will bite down nicely without the heat, but they'll tend to wear much faster if cool. Other race pads won't feel like they're catching at all when they're cold, and you won't get them to a good operating temperature on the street unless you're doing something illegal.

If you're going for just street driving, just get OEM, or something like Pagid (these dust a lot though). Unless you're at track speeds and threshold breaking, you're wasting your money on race pads since stock will slow you down just fine. Same with rotors, unless you want that cool look of cross-drilled or slotted. Steel lines are probably the only worthwhile upgrade for a street driven car. Once you go beyond street driving, begin to worry about the pads and rotors, and tires for that matter.

[niq_nak]

i thought the mintex reds were a good street pad, just like the pagids?

[modifiede30]

Sorry, when I saw "red", I interpreted it as a race pad since my are hawk "reds" and it seems a lot of pad companies use "red' to designate the pad as race.

[e30Matt]

Sorry, when I saw "red", I interpreted it as a race pad since my are hawk "reds" and it seems a lot of pad companies use "red' to designate the pad as race.

[Skafrog]

Drilled rotors tend to get stress cracks easily, expecially those Zimmerman ones.

Not true at all....

My car has had Zimmermon X-Drilled on it for while now. After about 6 track days they are FINE! My car goes a little faster most E30's, and gets driven FAST & hard at the track. My front calipers are also not stock.

I do not think so. Take your rotors under a magnifying glass and tell me what you see.

What usually happens is people try to use them past their wear limit, and they start to stress crack at the holes. You know what? Solid and slotted rotors will do the SAME thing!

True. Either ones are not good for the track. Look at a professional Touring Car team NOT running carbon rotors.

If there was no advantage to the x-drilled, why are Porsche, Ferrari, etc.. all using them in their Supercars?

Visual Effects, and they know that 95% of people will not heat them up enough. Still a mystery to me.

All that stuff on the site is taken as Gospel? Why it's some Ricer site, with no science to back any of it up, it's just internet rumor. As usual it's being spread as fact!

Corner Carvers is not a ricer site. Read the link before you start to trash. The thread started out with morons saying exactly what you said, and then MadMutt and Cobra from corner carvers came arond and spoke the truth. If you read his posts, he is a thermodynamic engineer.

With anything, you have to get QUALITY parts, taking a OE rotor and drilling holes it makes the rotor really weak, and prone to warping & cracking. You need CAST rottors, and when the radius hole is gone, the rotors are gone.

There are a few reasons for the holes.....
1. outgas of pads
2. create MORE surface area to aid in cooling
3. to help keep water off the brake surface.
4. lighter rotor

1) Outgas? No pads do that enough to matter anymore. Call stoptech brake systems and ask them this.
2) You sir are a moron. How do you figure? How is drilling DOWN into the rotors going to help create more surface area on the swept part of the rotor?
3) Uhhhh....... WTF? How the hell do holes help escape water when the rotors are turning at rapid speeds?
4) HAHAH. You save 5 grams total, and increase stopping distances.


Slotted rotors...
1. Outgas
2. scrape the pad clean, this helps stop glazing and crap getting stuck in the pad
3. water escape
4. aid in cooling

#'1 and #4 are Ricer Myths. Sorry.

Anyone with ATE power disk will know the pads don't last as long, and they dust more, it's due to the pads being scrapped by the slots.

Why is this beneficial? Slots were created for rally purposes, to clean the pads of DIRT. Not glazing.

Correct. They also help in street situations with initial bite in wet conditions.

On a street car, X-drilled are really just for looks. In brake performance, PAD choice is MORE important then the rotor. OE is best for most stuff.

Agreed.

SS lines, they are worth it...
1. You get new CLEAN lines
2. they are much stiffer
3. they are stronger
4. they will last longer

Agree 100 percent, but stiffer is not the correct word, unless you mean by limiting internal expansion.

WATCH OUT FOR EBAY! A lot of the super cheap stuff there is just that SUPER CHEAP! Most is made in China stuff, I doubt the Brembo rotors are even real brenbo rotos.
Also a valid point.

To beef up my reply, read this.

From a Brake Tech Article: Not Mine!

quote: Crossdrilled rotors-by design, crossdrilled rotors were designed for track use. Why? Because, when you drill holes in your rotors, they are designed to dissipate heat (not to rid of brake dust as most people think).

I found the root of your problem. It is right here. You don't know the definition of "dissipate". You also don't understand the interaction between a rotor and the pads. Here is how it works. The friction between the pad and rotor is what causes you to stop. This friction converts your forward energy into heat (remember Einstein: Energy is neither created nor destroyed, it is converted). Now that heat is a bad thing. Yes it is bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like shit. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Notice that DISSIPATE and DISPERSE are interchangeable? Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? That's right - number 3. Here is the list again. Memorize it because I will be using it a lot in this post:

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle

#2 DISSIPATE the heat

#3 REMOVE the heat from the brake system


Let's look more in-depth at each step now shall we? No? Too bad assclown we are doing it anyway.

#1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle:
This one is pretty simple and self-explanatory. The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you want) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. Does that make sense Ace? Good. Let's move on.

#2 DISSIPATE The Heat:
Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at VIR at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into. Make sense? This isn't rocket science here d00d.

#3 REMOVE the heat from the brake system:
Now comes your favorite part of the process. This is what you thought DISSIPATION was. It is ok. I will allow you to be wrong. This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it. Got it? Good.

Now let's look at why cross-drilling is a bad idea.

First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays.

Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause.

Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. Explain again just how drilling away material/structure from a CAST product DOES NOT weaken it? Since you are obviously a man of great knowledge and experience surely you have seen what can happen to a x-drilled rotor on track right? Yes it can happen to a non-drilled rotor as well but the odds are in your favor when pimpin' bling-bling drilled y0! Since you are also an expert on thermodynamics why not explain to the group what happens to a cast iron molecule when it is overheated. I will give you a little hint - the covalence bonds weaken. These bonds are what hold the molecules together boys and girls. You do the math - it adds up to fractures.

So why don't race teams use them if they are so much better? Consistency? Hmmmm . . . no. I am gonna go with the real reason her chodeboy. It is because of several factors actually. They are as follows but in no particular order:

- Less usable surface area for generating friction
- Less material to DISSIPATE the heat away from the pads
- Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material

And what are the benefits? Removal of particulate matter and enhanced heat removal. I gotta tell ya - it is a tough choice but I think I am going to stick with the safe, reliable, effective-for-my-stopping needs solution Tex.



Edit: Before I forget. Last weekend at the track, a supercharged NSX broke 4 slotted STOPTECH rotors. Not low end. A highly modified e36 m3 (3.0 euro motor, many upgrades, going just as fast) did not have a SINGLE brake problem. Not even warping.

[modifiede30]

Although the general tone of this thread has gone to all shit, the information is quite good. Skafrog's explanations make a lot of sense. I'll throw in some of my personal experience with slotted, x-drilled, and stock OEM rotors and pads just for fun.

The x-drilled seem to bite much better than the slotted or oem when using street pads and for daily driving. This seems particularly true in the rain, but in these conditions, the slotted rotors are just as good if not better.

The slotted rotors are much better on the track than either the x-drilled or oem, but I've had problems with warpage (also using x-drilled). Again, this is using the same overall brake setup, except rotors (and the same tires).

In general, if you haven't taken your car to the limits of adhesion yet, you should take a track session (actually, several) and learn to drive before you do anything to the car. A stock 325i is more than most people can handle until they've taken the car through a few sessions. This will at least get you familiar with breaking thresholds and the cornering abilities of the car. Then you might want to start worrying about suspension and braking. After that, I'd re-read Skafrog's post so you know what you're looking for.

[C ///M]

Skafrog, while your info is great, you are a complete asshole.

First of all, you have no idea who you're talking to, but you will eagerly direct the word "toadie" at me.

You say you are just trying to set the record straight, but you do it in an extremely poor manner. My post did not mention anything about "not arguing with the man."

Secondly, his post was much easier to read and better organized while straight to the point. This is why I posted it being a perfect post. I know you're not some young kid, but you act very immature by reading my post with a tone that I never intended or used while I was typing.

Thirdly, your original post was a little scattered and required users to read Half way down a 500 page thread of a whole ton of crap on an altima board. THIS IS NOT EFFECTIVE.

You will also notice that after you orignally posted, I thanked you for great info stating that all members should read it....

I suppose that makes me a "toadie" trying to hang off your balls? Get your head out of your ass and learn to contribute properly or not at all.

You still have not answered my question about Zimmerman's "cast-drilled" method which leads me to believe that you don't have any info on it and are only speaking from the experiences of your customers' stress cracks.

While I appreciate members like yourself with ties to parts companies, racing, and great information, learn to be mature and adult in your posts or don't post at all.

[Skafrog]

Hang on, I must point out that the bottom portion of my post (beyond the bold) is not mine, it is a copy of the original link. Instead of summarizing, I just copied and pasted, so if I came off harsh, I am sorry, I should have stated that it was from the original post so you did not have to scan through the 500 pages, thats just not fair to read so much info :-) I just can not stand people like APC selling drilled rotors, claiming they are better.

[Edit] Once again, I feel bad that I came off so harsh, I spend most of my time bitching about people being too mean. The board should be a place to learn without fear of getting ripped on. Once again, sorry, those were not my words below the bold. [/EDIT]

[jflower]

Chris, this was explained to me when i first started working by diversified cryogenics http://www.frozenrotors.com. 75% of their business is brakes, both on track and on street, as well as plenty of fleet vehicles like cop cars and delivery vans... not exactly easy going braking systems... in any event here's what happens with a rotor with holes in it (drilled or cast):

disclaimer, my terminology may not be perfect, but i feel i'm solid on the concepts.

the two main issues all of my customers have when they run drilled rotors (or cast) is warping and stress cracks in the holes. this is mainly due to unequal heat in the rotor. the holes cause heat to build up on one edge of the hole (i believe the trailing edge). At the office I have some "heat-sensing" photos of a drilled rotor. you can clearly see the spots of increased heat. obviously, when a rotor heats and cools un-evenly, it warps, and in time will crack.

-also, the brembo rotors i've sold with the big brake kits have all been cast rotors (with the holes). almost across the board our customers call us back in 4-5 months and order slotted replacements for the rotor face. others just get solid. i spend almost 5 minutes in a disclaimer whenever a customer orders their rotors drilled.

i agree with skafrog on the magnified appearance of rotors, however as we've all said, rotors will eventually crack no matter what (drilled/slotted/cast/heat treated/cryo treated) it's just a matter of how much heat gets in them, and how the heat goes in and goes out.

as far as i'm concerned, metallurgically i don't care why rotors with holes die faster. from my experience, we get almost three times the life with slotted rotors on a car driven primarily on the track. if you want the increased initial bite that a modified rotor gets you, slotted gets my vote.

easy on the fire, boys.

[C ///M]

I know Jay, thanks. Really, I do though. You guys are directing all of your x-drilling concepts at me, but I know. LIke i said, when i went through my brake obsession, i looked at all of this stuff.
Hell Jay, Either you or one of our BYers (i'm pretty sure it was you) give me that link you just posted.

I was just posting on what options are. If you read all most posts in this thread you'll see the pattern i was goin with, I PURPOSELY was avoiding the x-drilled discussions and only compared x-drilled brembo's with x-drilled zimmermans and presented my findings. Anyway... :dot:

[EVOIIIM3]

I do not think so. Take your rotors under a magnifying glass and tell me what you see.

1) Outgas? No pads do that enough to matter anymore. Call stoptech brake systems and ask them this.
2) You sir are a moron. How do you figure? How is drilling DOWN into the rotors going to help create more surface area on the swept part of the rotor?
3) Uhhhh....... WTF? How the hell do holes help escape water when the rotors are turning at rapid speeds?
4) HAHAH. You save 5 grams total, and increase stopping distances.


Slotted rotors...
1. Outgas
2. scrape the pad clean, this helps stop glazing and crap getting stuck in the pad
3. water escape
4. aid in cooling

#'1 and #4 are Ricer Myths. Sorry.

On a street car, X-drilled are really just for looks. In brake performance, PAD choice is MORE important then the rotor. OE is best for most stuff.

Agree 100 percent, but stiffer is not the correct word, unless you mean by limiting internal expansion.

Edit: Before I forget. Last weekend at the track, a supercharged NSX broke 4 slotted STOPTECH rotors. Not low end. A highly modified e36 m3 (3.0 euro motor, many upgrades, going just as fast) did not have a SINGLE brake problem. Not even warping.

There are not cracks on my rotors yet, I'm sure at one point they will have them, all hard used worn rotors will, mine right now do not.

1. Out-gassing, yes, some pads still do it, just not many street pads, and this is WHY the rotors were designed for, just because pad technology is better doesn't make it any less true.
2. Moron? Humm, that was uncalled for. I said NOTHING of swept area. I was was talking about rotor cooling area. Why does a golf ball have dimples? It increases surface area, think about it. I also have a really nice equation to figure this out if you want it.
3. What happens when you brake in the wet? What happens to the water on the rotor? It turns to what? VAPOR, and that needs to escape. It's like a tire in the wet, it will also push the water out threw the holes.
4. 5g? Come on, actually on my M3, they are 1.25lbs lighter! I would say that is a difference.

Slotted rotors...
1. yes they help with out gas, just live with it.
2. goes back to surface area, just look at a radiator, it has a great amount of surface area, if it was SOLID, would it cool as much?

If these things were just for "Looks" then they would not be on supercars, the Enzo, has nothing on there just for "looks" Also don't underestimate 2-3lbs savings per rotor, that is wheel HP gained there, you know most BBK you loose about 2-5% WHP.

SS lines
Stiffer in stopping thermal expansion, they are also physically stiffer over the rubber lines. They can take a lot more abuse then rubber ones.

Anyone, can toast any rotor & pad. Braking technique is very underestimated. I have seen low hp stock cars whip cars they never should even be on the track with. Once you reach the thermal limit of anything, it's going to fail. I've seen Porsche Big Reds crush a rotor out at the track.

For the record, Stoptech brakes are really a street setup, Brembo & AP are real racing setups. I'm not saying they are a great setup, they are just not up to the same duty as the others, and the GT Brembo kit is about the same as the ST setups.

Anyone who overdrives their brakes need to see what temps there getting to, there are some thermal paints out there that you put on the caliper and it will help you measure your working temp.

For the record, I'm a Physicist.

[modifiede30]

I'm not a scientist but some of this seems to be understandable for the lay person if a little common sense is used. Of course I could just be wrong but I'll admit once I know.

Given that the rotor is meant to act as a heat-sink (after doing its job of breaking), and that the transfer of heat from the pad to the rotor requires contact, I've always though the issue of rotor surface area was a misnomer to some extent. Shouldn't "contact area" be used when discussing the rotor's ability to absorb heat from the pad - how this heat is lost by the rotor is a different issue?

From a surface area perspective, I think both x-drilled and slotted have more of it. Anytime you take a flat surface and introduce changes in the surface, it increases surface area. That's why stereo amplifiers have heat sinks that are finned, and as mentioned earlier, radiators.

However, it would seem that the loss of the "contact area" reduces the rotors ability to capture heat from the pads, resulting in higher pad temperatures. Also, isn't the new surface area gained with x-drilled rotors created in a location that is not as exposed to air as the rest of the rotors. Seems like this would tend to keep the holes and surrounding areas much hotter than the rest of the rotor surface which has a lot more exposure to air.