Is there a weight savings, blanks vs. slotted?
Is there a weight savings, blanks vs. slotted?
trigun7469 wrote: Is there a weight savings, blanks vs. slotted?
i would imagine a good poop would lose you more weight then the amount of material that is removed from a slotted rotor
SilverFleet wrote:wvumtnbkr wrote:This is relevant to my interests. I did brakes all around on my Mazda 3 about 15k miles ago. In the past couple months, I've noticed a low speed scraping noise coming from up front, and at highway speed the wheel will shake like a mofo, more so when I apply the brakes. The very same thing happened to my 2009 WRX, and I used the very same pads and rotors on each car (Centric blanks and Stoptech Street Performance pads). I will pop off the fronts and scuff/re-bed the pads and see if it helps.gearheadE30 wrote:Because anytime somebody brought me a car with "warped" rotors I used sandpaper on them to get rid of the pad deposits and rebedded in the pads. No more warped rotor. I can guarantee that I did not make them "true" by hitting them with sandpaper (or sometimes an angle grinder if really bad).wvumtnbkr wrote: I do not believe in warped rotors. I DO believe in uneven transfer of pad material onto the rotor which causes pulsing and vibration. I have also seen crappy rotors have "hard spots" on the face which can do the same thing.I agree that pad deposits and hot spots (local hardening) are probably more common than true warping, but why don't you believe in warped rotors?
You need to scuff teh rotors too.
Also, I would be looking for a slightly hung caliper (like the slider pins need lubricated). The scraping while driving and not touching the brake implies something else going on.
This slight scraping can lead to excess heat buildup and uneven pad material transfer which WILL cause the vibration under braking.
TLDR: Check the sliding pins while you are in there.
Scalloped rotors are the answer imho
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99.99% of the brake issues I've seen people have are due to improperly cleaned and lubricated slides. If the pads can't move the brakes don't work. The great majority of "techs" and backyard mechanics do a poor job (if any) of cleaning the rust and brake dust from the surfaces the pads move across and they are rarely lubricated at all.
Rusted_Busted_Spit wrote: I hear this about drilled rotors all the time and I do not dispute what is being said but it does raise one question in my mind. Porsche, to my understanding, has some of the best stock brakes you can get in a street car and a lot of them come with drilled rotors. Is it really just a fashion thing for them or do they see some benefit?
The biggest difference is E36 M3ty drilled rotors are blanks that were drilled. Obviously, that is teh fail. The good ones are made much differently and strangely don't have many problems. 
As a couple of others mentioned, clean the rotors when you change pads. I did this on my ZX2SR that was track dayed, hill climbed, ice raced an DD. Never a rotor problem. Also my KJ which towed the trailer. This was for 70+K miles.
Smooth rotors it is! And of course the follow up question is pads. I can get ebay smooth rotors with ceramic pads on all 4 corners for about $25 more. EBC pads look to be about $60 per axle. Worth the difference? Calipers will be serviced, hoses inspected and good fluid installed...
trigun7469 wrote: Is there a weight savings, blanks vs. slotted?
The major point is for improved stopping power. Larger rotors weigh more than smaller ones, yet no one complains that you will weigh the car down.
My experience with ceramic, and also ebay brake kits and stopping distance is lengthened...they don't stop well at all, ceramics like to eat rotors before the pads are due again. For a cheap upgrade over stock I like the stoptech performance pads from rock auto, not as grippy as hawk hps for instance and dust more but great cheap upgrade. Ebay drilled and slotted is fine for street (for looks) but anything more severe they can crack
I actually think i may need drilled or slotted rotors on my daily driven protege5. Purely due to wet weather braking. With wet rotors, I have no brakes for a couple of seconds.
The last thing i experienced this on got drilled rotors and it solved that particular problem.
Car is equipped with mazdaspeed protege brakes and pfc pads. Ideas?
In reply to Dusterbd13: Go with slotted rotors. Many people, including me have found that drilled rotors don't improve stopping power.
My two cents:
Drilled/slotted rotors aren't really a benefit on anything other than some extreme unobtanium engineering. I did buy a set for my Impala SS years ago and they have held up nicely and I did resurface them once (turned on a lathe).
The theory is sound. Outgassing from hot pads supposedly creates a barrier and reduces braking in extreme conditions much like an air hockey puck floats on the table. But I can't imagine with modern pad materials that it is an issue. The main reason why they can't be resurfaced is because the drilled holes are chamfered to reduce noise and pad wear, but mine were chamfered deep enough that there was plenty of surface to machine without taking away the easement.
My theory is that drilled/slotted rotors came about as a fix for outgassing on old-school organic pad material. These days no one uses organic pads, least of all in racing so its probably a non-issue. I did know a guy who autocrossed an F-body and he specifically used organic pads to save his rotors. (dumb choice in my opinion, but his car) In the hard braking at the exit lane you could see puffs of smoke and reddish puffs of flame from his pads. After seeing that, I could imagine that drilled/slotted rotors might have helped in that situation.
... but so would using pads with technology newer than 1940.
In reply to curtis73:
NAO = non-asbestos organic and they're used pretty much everywhere in the auto industry.
The weight CAN be significant. Anyone remember (maybe it was Andy holis) the brake rotors that we drilled so much there was more hole than metal? They lost like 7lbs (nearly 10 % or something) of rotating unsprung weight on a lightweight autox er?
Also, big brakes can add a significant amount of weight to a vehicle, and I would almost never recommend them to an autox car.
Side note, when talking about brakes, please remember that it is not stopping power you are trying to increase (show me a car that cannot lock the wheels up with good functioning stock parts). Rather, usually the goal is to increase resistance to fade.
To the op- i doubt slotted or drilled will give you greater resistance to fading (in fact they might do the opposite). I think you are on the right track with solids. Spend the money on good pads though.
AngryCorvair wrote: In reply to curtis73: NAO = non-asbestos organic and they're used pretty much everywhere in the auto industry.
We agree, but I should have clarified... no one who would be concerned with peak performance in upgraded brakes would use technology from 1940. I have organic pads on a couple vehicles and they work fine to stop a vehicle.
I'm saying that with the newer pad technology out there, using drilled and slotted rotors to overcome organic pads' shortcomings is not the best way of doing things.
I don't have much hands on experience with slotted/drilled rotors. I do know that the combination of stock rotor blanks and Porterfield R4E pads on our LeMons Civic impressed me so much that a similar setup is on the front of the Jensenator. In several 20-25 minute sessions at CMP and Road Atlanta, no fade or etc.
wvumtnbkr wrote: I do not believe in warped rotors. I DO believe in uneven transfer of pad material onto the rotor which causes pulsing and vibration. I have also seen crappy rotors have "hard spots" on the face which can do the same thing.
Pulsations stem from many sources. One is uneven pad transfer causing varying levels of grip. Another is uneven rotor wear from the rotor having runout when installed for whatever reason, and the high spots get knocked down from just driving along and grazing the pads every revolution. This is the pulsation that starts 3-5000mi after putting new rotors on.
But rotors can and do warp. Iron can "twang" after final machining, especially after a good heat cycle or two. This can generally be corrected by remachining and then they will be good forevermore. But rotors are often cheap, with a good amount of core shift. The rotor thickness may be consistent but what if the thickness of the metal varies by 20-30% because the vanes aren't centered? How do you think that is going to respond to being heated by the pads? The thinner spots will get hotter first and expand more, not just thickness-wise but also diameter-wise and it gets even more goofy when you figure that due to the nature of core shift, only one side will want to expand, maybe on opposite sides 180 degrees out if the core shift is diagonal. That is definitely going to warp the rotor like a potato chip and it may not settle back down to where it used to be. Crappy castings with a lot of core shift usually present as rotors that are fine until you get the brakes hot and then they start thumping.
This is all before the temperature gradient across the rotor diameter. The friction surface gets really hot while the hub doesn't, and is clamped to a nice big heat sink (the wheel). And so is why performance rotors, real ones, have a separate rotor hat and there is an allowance in the mounting for the rotor to grow diametrically.
Rusted_Busted_Spit wrote: I hear this about drilled rotors all the time and I do not dispute what is being said but it does raise one question in my mind. Porsche, to my understanding, has some of the best stock brakes you can get in a street car and a lot of them come with drilled rotors. Is it really just a fashion thing for them or do they see some benefit?
Porsche is selling to people throwing a lot of money around. A lot of things on the car aren't for performance, they're for appearance. Drilled rotors definitely look badass. People who drop $100k on a Porsche want their brakes to look as badass as the rest of the car :)
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