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Discussion Starter · #1 ·
i think one or both of my front rotors is warped. at high speeds, when i brake, the steering shakes pretty violently. my first guess would be the rotors have been warped.

where i am at 28K miles, will warranty give me new rotors? i don't want them to just turn them. also, will they say this was regular wear and tear?

i'm bummed about this. betty has been trouble free since i got the defective clutch replaced 10K ago. (except for that stinking "screeeeeeee" on the driver's window)

any thoughts on other causes for the steering shake? SOA's reaction?

dR
 

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warped or cracked are both possibilities. My guess would be that SOA are unlikely to give in on 'fair wear and tear' I know that when I cracked mine on my '94 WRX back home - there was nothing but my caning the brakes that caused it.

They get very very hot and then cool too quick and hey presto! a crack opens up along the vent vane line!

If they are cracked they need replacing - get slotted rotors to replace them. If they are warped - hope there is enough meat on them and get them machined and start saving for the slotted rotors!

PS: how high is 'high speed'??
 

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Discussion Starter · #3 ·
the typical 80mph on the hwy.

even at 55 or less, a firm brake will not shake the car. that's why i don't think they're cracked, (or if they are, it's got to be pretty minor)

my opinion is, if they are getting hot enough to warp with my wheels (wide open 7 spokes, 17") and not track use, they should be replaced under warranty. i drove the same speeds in my 91 corrolla, and never warped or cracked a rotor. (actiually, they were still OE after 117K miles, only turned, w/ new pads a few times)

wouldn't cross drilled cool faster than slotted? i'm a n00b to brake upgrades, is it just a cost decision there? i've read about wilwood, stoptech, and brembo. what other options are there? if i go with better cooling rotors, can i chince on the pads? i imagine they'll be less susceptable to glazing, so i might get away with something like a bendix pad. i'm not a track or strip driver, just 95% highway.

dR
 

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cross drilled will cool faster but are more prone to cracking. The slotted gives a large surface area to dissapate heat without providing the same seed for crack propagation.

Cracking is also caused by the rotor not cooling uniformly.

It is not that they are getting hot enough to warp - it is the fact that they are cooling too quickly or not uniformly to warp.

The wheels you are running will probably make little difference to the stock brakes.

I am still running the stock brakes and am looking for a 4 pot kit that fits under the stock 16" wheels - there is a perrin/wilwood kit that looks pretty good.
 

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Discussion Starter · #5 ·
i understand that it's rapid/uneven cooling, but my point is that that sounds like a design flaw.

no?

typically, that would be a symptom of an after market wheel blocking or disturbing airflow in the well. but mine are so open faced, i figured just the opposite.

should i go aftermarket? i could throw in some shi+ from my dad's store and save a ton if warranty won't cover me. but if i really should stay OE (i think they're hampden, not sure though) i'll just upgrade to wilwood or something nicer. i'm just pissed. i don't even have the go fast mods to warrant an upgraded brake package.

dR
 

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The way that you brake can be a factor - do you ever find yourself 'riding' the brakes?

This is only speculation - but the more open wheel may contribute to en-even cooling. I am only doing the devil's advocate thing on SOA lawyer type thinking.

I can understand you are pissed -

If you do not have go fast mods, just replace with stock if you can get good prices. I went to slotted back home because there was only a 10% price diff and my cracked ones were only good to be used as a door stop.

If your stockers can be machined - go for that.

My 0.02
 

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Thinking Man's Engine
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Wear Item Limited Warranty
Wear item coverage for all models except Right-Hand Drive Legacy is 3 years or 36,000 miles, whichever comes first. Items covered include brake pad/shoe linings, clutch disk linings, and wiper blades.

Straight from their website, so you have a chance.

For cross-drilled....it only happens in extreme cases of racing. Porsche still uses cross-drilled brakes.

For your day to day driving....cross drilled will be better than slotted, only because you'll get increased pad life compared to slotted (milled out rotors).
 

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Discussion Starter · #8 ·
nevermind ride them, i barely use them. i generally engine brake or downshift b/c i'm on the hwy so much. even on ramps i find my self only braking when i need to come to a complete stop, or save my life.

i'll call them tomorrow, and get back to you guys.

anyone know what brand the OE rotors and pads are?

dR
 

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Sorry to hear of your problem, dark_rex.

Somebody else here posted their rotors were warped. It was Platinum WRX if I recall correctly. I would say your options are threefold:

1) The dealer replaces your rotors under warranty (unlikely, I should think - but worth taking a shot anyway), or agrees to machine them for you.

2) You have them turned yourself. What would be the objection to doing this - concern that warping would just happen all over again ?

3) Upgrade your brakes.

The choice between just getting them turned and upgrading your brakes really comes down to how you intend to drive the car. Are you sure you will never, ever do an AutoX or a Track Day ? Then the stock brakes should be just fine.

But if you even think there's a chance that you might enter a competitive event, then upgrading your brakes is the right thing to do. There are many levels of upgrade, from just doing pads / fluid to full-out big brake kits. I've chosen the low budget route and the results on the track have been adequate and the brakes are just fine for daily driving. I've had no problems with the cross-drilled SPOs. They also fit under the stock wheels and no adjustments are needed with using the OE calipers.
 

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There's a good chance that what you're feeling is built up pad material on the rotors. That would explain why you don't feel it with firm pressure.

You could try having them bead blasted - a machine shop will probably be able to do it, or a specialist. Don't pay more than a few bucks. Or just try srubbing them with steel wool and brake cleaner.

Chris
 

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whats it called when they take the rotor and shave a bit of it off? i know it reduces its capability b/c ur removing some of the rotor, but at least sanding it down will smooth it out...right?
 

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I don't think cross-drilled is the way to go. I've read a lot of stuff that was written by experts on why. Although I don't have the expertise to back it up, they certainly do.

Basically cross drilling was used back before technology advanced with brake pads. I believe they were put there to get rid of air pockets or something under the pads, IIRC. Slotted rotors are more useful because they can take things like mud or debris and send them out from under the pad, without giving up the surface area. The most important thing about a brake rotor is surface area, which allows for more heat removal from the pads to the rotors to air.

If I were going to upgrade, I'd go with slotted rotors (or solid). For my needs for autox next season, I will be upgrading fluid, lines, and pads, but keeping stock rotors unless I develop a problem with them.

tcc
 

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My car shakes badly too. It only does it when i brake semi hard (or harder) at speeds above 60... is this what you're experiencing dark_rex? I only have 7000 miles and i don't ride the brakes.
 

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Penguinking said:
whats it called when they take the rotor and shave a bit of it off? i know it reduces its capability b/c ur removing some of the rotor, but at least sanding it down will smooth it out...right?
That is machining. The reduced thickness doesn't reduce the braking capability unless you machine them beyond the manufacturer's minimum thickness (in the shop manual)
 

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thechickencow said:
I don't think cross-drilled is the way to go. I've read a lot of stuff that was written by experts on why. Although I don't have the expertise to back it up, they certainly do.

Basically cross drilling was used back before technology advanced with brake pads. I believe they were put there to get rid of air pockets or something under the pads, IIRC. Slotted rotors are more useful because they can take things like mud or debris and send them out from under the pad, without giving up the surface area. The most important thing about a brake rotor is surface area, which allows for more heat dissipation from the pads to the rotors to air.

tcc
Checked any detailed photos of the new Ferrari Enzo ? Cost be damned, it will be the finest street-legal sports car on the planet. It has cross-drilled rotors.

Here is my understanding of it. The extreme heat generated by hard braking tends to make the pads outgas. This will build up a layer of flim between the rotor and pad causing brake fade. Cross-drilling and slots are two approaches to addressing this issue. The idea is to vent these gasses to prevent any buildup as well as to provide cooling. If anything, cross-drilled rotors should be slightly superior at this task.

The drawback of cross-drilled rotors is that they tend to be harder on the pads than slotted rotors due to the less uniform surface presented to the pad. Your pads get chewed up faster. The other Achilles heel can be stress-cracks radiating out from the holes. Cross-drilling undermines the structural integrity of the rotor if done improperly. My SPOs are a one-piece casting and the holes are nicely chamfered, so I think the risk is of cracking is minimal.

I'm not saying that cross-drilled is better. Prevailing opinion seems to lean towards slotted but either type of rotor upgrade will be superior to the stock rotors. Increased surface area will provide more stopping power (more volume of swept area), for example, front rotors are always bigger than the ones in back. But they will not necessarily provide better heat dissipation w/o cross-drilling or slotting.
 

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I didn't have the time before to find this link, but here it is:

http://www.surrealmirage.com/subaru/brakes.html

And here's a thread from altimas.net that has some good info mixed in with a bunch of BS. Pay attention to the posts by "Cobra" which are on the 3rd page. He exhibits some SERIOUS OWNAGE of the people that act like they know what they're talking about. This should take you to the page, just scroll down to his post to get an explaination.

http://www.altimas.net/forum/showthread.php?threadid=32327&perpage=15&pagenumber=3


tcc

Screw it...here's his post...

Post by Cobra on altimas.net

quote:
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I am going to be opinionated here for a bit, just like in the other post (the DZ coilover post). I am kinda tired of unqualified answers, so I speak from a personal and professional experience with brakes.
Here we go.
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My advice - pick a new profession. Something simple. Perhaps - a Wal-Mart greeter. Your qualifications are almost adequate for that.

quote:
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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).
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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 ****. 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.

Finally let's talk about you. You should be ashamed of yourself. You are obviously regarded as a sort of demigod here. I am not quite sure why but the little toadie sticking up his fingers and saying "don't argue with THE MAN" is evidence that there are quite a few lemmings here just waiting to follow you off the nearest cliff. A vendor should really take knowledge and understanding of the products he recommends and sells a little more seriously. Further - who the fvck quotes Super Street as a reliable source of tech info of any kind? That smut is as useful for auto tech as is Cosmopolitan. Only a fool would EVER use claims made by that publication as facts in an argument. Your bad advice is going to get one of these new guys killed because they think you know your ****, they are going to take your advice, and then they are going to careen head on into a retaining wall at 120MPH because the part YOU recommended them failed at race speeds. Fvck you ****head! You may not care if that blood is on your hands but I will do what I can to make sure it isn't on mine.

Most of you lemmings will stick your little fingers up at me but I know a few of you will read my words and the words of the others here who are trying to set the record straight. I don't expect any of you to take any of this advice here as scripture. I urge you all to go and do some research. Talk to more than just the dickhead in this thread. Find out what people who ACTUALLY race are doing and why they are doing it. I have news for you all. There is no "better" idea. It has all been done before. If it worked people would do it now.

Commence the banning since I am not willing to swing from the jock of this fool.
 

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Well, Jay - we're in some danger of highjacking dark_rex's thread here, but here goes:

1st link - Well-reasoned. I don't think it really contradicts what I posted. Interesting that he states the leading cause of rotor warpage is heat / cool cycles, running it hard so that the heat soak from the pads/calipers will cause warpage in that portion of the rotor. Very plausible but that hardly seems to be dR's situation, given the info he has given us.

2nd link - The Cobra ? Some rude *sshole posting on an Altima board ? LOL, dude. His opinion is no more credible than yours or mine. What truly expert racer interested in helping others would post something like that ?
 

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I still think that the post by cobra was well reasoned, and he knows what he's talking about. (read 2 posts down on the altima board post for his credentials)

Either way, doesn't matter to me. I am in agreement with him, and will probably never put cross drilled rotors on a car I have because even with autox, rallyx, and occasional track days I won't push my brakes hard enough to need to worry about it. Like I said before, I don't doubt that a cross drilled rotor will perform better than stock, I don't think it is ideal for pretty much anybody on this board. If others choose to fine, I personally just think they are more for show than anything else for 99% of the people that put them on their street cars. I wonder what Gary S. puts on his car.

sorry to continue the hijack.

tcc
 

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Penguinking : it's turning the rotors. After it's turned on the lathe, the finishing operation is manual sanding in a circular motion, so that pads will bed properly.

missed reason also: Anyone want to take a gander at what causes "brake fade"? Heat from the rotor and the pads release a gas which reduces the pad to rotor contact (it's like hydroplaning). Slots and holes allows for displacement of that gas, to maintain the pad to rotor contact.

Yes, many people will encounter still this on day to day driving if caught in situations of long stop-and-go traffic.
 

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Discussion Starter · #20 ·
blackshadow said:
My car shakes badly too. It only does it when i brake semi hard (or harder) at speeds above 60... is this what you're experiencing dark_rex? I only have 7000 miles and i don't ride the brakes.
same exact thing.

brake fade is caused in part by escaping gasses from the heat transfer, but more oftenly, and almost ALWAYS on the track, from increased heat glazing the pad surface over. cross drilled rotors are designed to dissipate/disperse :rolleyes: heat. slotted is for the removal of gasses, heat, and excess material/glazing from the pad.

if subaru tells me their going to turn my rotors, i'm walking out. i've turned rotors since i was 16 in the back of dad's store. i can do that myself, and not have to worry about the tech taking betty for a joyride (caught them twice doing this)

i'm a good salesman. they'll be replaced if i have anything at all to do with it.

that guy like to make himself sound smart (in the nissan thread) i'm sure he's qualified, but braking is NOT that complicated. he just wanted to belittle someone imo.

dR
 
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