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RIP 08.24.2013
01 legacy L
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8,015 Posts
el-cheapo blanks
Metallic brake pads. = many panic stops due to assclowns, heavy braking before corners, panic braking at lights that decided to change.

No brake fake and a solid feeling pedal. The only thing I think that would improve the feeling of my brakes now would be SS lines.
 

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'99 CoupeRS BDP
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113 Posts
Corvette Forum - View Single Post - Drilled Rotors vs. Slotted Rotors.... Engineer test..

For those that are interested in upgrading from a stock rotor to either drilled or slotted, read this from an engineer's stand point. I helped me make my decision to just get drilled rotors on all four corners. Thank..

There are many claims as to the benefits of drilled vs slotted rotors on stopping power. This guide is intended to provide some facts about drilled and slotted rotors. As a member of the SAE (Society of Automotive Engineers), I was pleased to see a paper "The Effect of Rotor Crossdrilling on Brake Performance" by two GM engineers published in 2006. They examined three vehicle platforms with cross-drilled rotors vs standard rotors to measure convection cooling capability, fade characteristics, wet braking, pedal feel and lining wear. The result is summarized as follows:

For the sports sedan, the coefficient of friction was 21% higher for drilled rotors than standard front rotors at 340F and higher using 15 brake snubs at 62mph. The track simulated 124 mph fade test showed 37% better brake output for drilled rotors. The drilled rotor brake temperature was about 150 degrees cooler.
For the performance car, the coefficient of friction was significantly higher for drilled rotors especially at high temperature.
Wet braking at high pedal pressure was the same for drilled or standard rotors. Wet braking is not significantly improved by drilled rotors.
Pedal force was much more consistent with drilled rotors over the brake temperature range. That is, to stop at the same deceleration rate, the driver does not need to modulate pedal pressure based on different brake temperatures. This reduces driver fatigue and improves brake response.
The authors also reported that drilled rotors prevent pad resin glazing on the rotor. So we now have solid evidence that drilled rotors have benefits over standard rotors. However, I have not found any published paper to show how slots affect brake output. So I reviewed inertial dynamometer tests using ISO NWI 26867 from Link Testing in Detroit with slotted rotors vs standard rotors. The results showed no significant difference in the coefficient of friction during the fade sections, hot stop section or pedal sensitivity portion of the test. My hypothesis is that slotted rotors do not contribute to rotor cooling whereas drilled rotors improve convection heat transfer to cool rotors and reduce brake fade. I should also point out that the pad lining wear for the slotted rotor was very severe during the test, i.e. the pad was chewed up over 20% more than the lining with stock rotors. While I believe that slots will help remove gas and debri from under the pad, I am not sure that this has a significant effect on brake torque for normal street driving. Perhaps the effect of slotted rotors is more significant on the race track, and conversely, I believe that drilled rotors are better for street and highway driving. For most drivers, I recommend drilled rotors over slotted rotors, and this conclusion is supported by the fact that Corvette, Ford GT, Porsche, Mercedes and BMW come with OEM drilled rotors.
IMO, the most important find is the coefficient of friction between the slottend and standard rotors were nearly identical.
 

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'99 CoupeRS BDP
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113 Posts
With my '12 Mustang, I am a fan of cheap and effective products since I do a lot of track days across the US. I can get a full set of new OE rotors and EBC bluestuff racepads all around for under $275, shipped to my doorstep! Look for good reviews and obviously price when deciding what your next brake upgrade should be.
 

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99 Forester L, 5 spd
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1,306 Posts
After reading this entire thread I have decided to go with slotted rotors and upgraded pads/fluid in my WRX swapped Forester.


Posted from Rs25.com App for Android
 

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2001 D2 A8L
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929 Posts
If only all the engineers could agree. Funny how both sides of the arguement can be backed up by experts in the field.

I personally don't see the use of reducing your frictions surface while driving on the street.

I don't think this is one of those things you can just argue. Actual testing in a laboratory setting is the only thing that will convince me.
 

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I have a 3000GT VR4 that I run pretty hard on the street on a downhill course. let me tell you what - I'll never outfit my car with cross drilled rotors again. I did once. Within half a year, they were cracking in the front around several holes. They never warped, and they did perform well, but I'd rather replace pads than rotors. slotted on all 4 corners for a year, same braking performance. Get some good brake fluid, decent pads that match your application, and don't buy more rotor than you need.
 

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2005 Baja Turbo
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1,448 Posts
I got the front rotors on my 2000 Legacy L to glow so bright that it was painful to look at at night.

Same with my 1998 Legacy GT with WRX front brakes.

And the same with my 2002 WRX.

And my Dad's 1995 Toyota T100 (those ****ers warped to hell and back as well).

All of these cars ran blanks up front, and other than the T100, solid blanks in the back, too. T100 has drums...

If I had the money, I would go with carbon fiber discs all around. But I don't have that kind of coin, so I'm probably going to upgrade to Slotted front and rear on my WRX.
 

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99 L
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96 Posts
I had DBA 5000s cross drilled and slotted on my 08 sti, they stopped on a dime but I continually had to get them lazed. I would have much rather had slotted over both cross drilled and slotted. And trust me, I broke them in properly and on each track day I would be extra careful on how I heated them up prior to laying in to spirited driving.
 

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1999 Subaru 2.5RS
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196 Posts
The slotted vented stoptech rotors have served me well for a couple track days. I have them paired with hawk hp+ pads.
 

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97 impreza outback sport
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43 Posts
I've seen a major difference in my braking since I ran Drilled/slotted rotors. i used to have Forester calipers and blank rotors on my daily OBS and it stopped good, however i went back to OBS calipers and drilled/slotted plus SS lines... Holy crap... :naughty: amazing difference.
 

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1996 imp jdm ej20 NA dohc swap
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400 Posts
As 1 person mentioned earlier in this thread, lets take the 01-03 outback H-6 rear 290mm rotors and why it is such a good upgrade over the 260mm rear rotors that come on so many of the subaru cars and especially the cars that came with rear drums like my 98 imp L sedan.

The main reason is for more balanced braking front to rear, the rear end feels more planted. I installed the outback H-6 290mm rear rotors on my 96 imp outback (has 294 mm wrx rotors on the front) that already had stock 260mm rotors from the factory. The rear end did not feel as tail happy but more planted especially when braking while going through a turn or in a straight line. Same thing happened when I went to the 260mm rear rotors on my 98 imp L sedan 4eat that had rear drums. Felt more planted and "safer". Though it was only the 260mm rotor size it still made a difference over the drums. Has 15" wheels hence why only the 260mm rear rotors as an upgrade. This was with stock pads on the 98 and the stoptech street performance pads with centric blanks on my 96 imp wagon. I know for a fact that a larger size rotor makes a difference even with stock pads for the rear anyway.

Now lets look at the front for a moment. The argument is that heat is the issue, NOT ON A STREET CAR IT ISN'T...PERIOD! How many subaru owners run stock passenger tires on their rs's or wrx's or sti's? basically NONE. Higher performance/stickier tires do help, but as it was mentioned more than once certain components need to be upgraded together like tires and brake related stuff like pads, rotors, lines (optional, but why not) and fluid for a street car or auto-x stuff. You upgrade tires for a more sportier feel (stiffer), better look and grip. You upgrade the brakes for more efficient braking ability. Now you have a balanced, but upgraded tire and brake system "if" you have bought the correct components for your car for street, auto-x or both. People who auto-x understand this.

Since soo many people like to go to larger diameter wheels, that means there is the ability to upgrade the rotor size from the wrx 294mm front rotors to something like factory sti 326mm fronts or even the 05-08 legacy gt turbo 316mm front rotors. The rears would be appropriate with the fronts of course. Same thing goes for myself that went from the 266mm front rotors to the wrx 294mm front rotor or the 2.5 rs guys who went from the 276mm fronts to the wrx 294mm front rotor or the sti 326mm front rotor and corresponding rears. There is increased brake torque due to a larger diameter disk. Puts the clamping force further from the hub and towards the outer diameter of the wheel. Basic physics right?

So we have heat, brake pads need enough heat to work properly especially any upgraded pads with a higher thermo capacity (has a raised base temp before the pad starts to work) right? for 1 or 2 steps above stock pads anyway. We have coefficient of friction, stock pads have enough for comfort and everyday braking situations, for more spirited/higher speed/heavier braking, a pad with a higher coefficient of friction has a greater initial bite and friction throughout the stop or slowing down process, right? Ok, as what has been stated over n over, higher friction pads create higher amounts of heat, but they also can take the increased heat load due to the chemical make up or thermo capacity to a point. If a person is pushing the car past the thermo capacity of the pads, then trying a rotor with holes or slots isn't going to fix this situation. Going to a better metallurgy material rotor can help, but you then also have to upgrade the pads to take the increased heat over what a person was using before. Ever wonder why the big brake kits have a larger diameter rotor? Increased brake torque like I stated earlier. Bigger 4 or 6 pot calipers also help when getting to that point.

Racing brake makes a 1 piece 322 or 325mm front rotor with an extended caliper bracket for stock calipers for a subaru 02-05 wrx and 08-2012 wrx I believe and the rs 276mm and other na 266mm front rotors. Talk about an upgrade over stock, but much cheaper upgrade over sti brembo's. Granted it is the stock caliper, but for the price, not bad at all. You get increased brake torque due to diameter, but also increased surface area due to a larger circumference rotor. (no one has said anything about this yet in this thread that I read). But there we go, stock steel caliper...blah..blah..blah.. If someone pushes their car past what this package can handle then the sti brembo's are the next step right? stock 4 pots found on the 06-07 wrx won't cut it (not like the sti brembo's) due to the limit of 294mm front rotors. Better metallurgy rotors yes, but the limit is the diameter of the rotors for this set up.

The next thing is about pads on a slotted, drilled or both rotor compared to a blank rotor, stock size for now. There were comments about blank rotors getting warped. This brings the question, what blank rotors were being used and where were they bought? Were they the cheap autozone or Orielly blanks? The centric blanks are a nice step above these cheap options. People blame rotors for a street car for getting warped, now the other questions are, are they using stock pads, or other cheap alternate pads that have inconsistent pad layer transfer? (haven't seen pad layer transfer talked about here either), are these people using a slightly more aggressive brake pad on a daily car, which can have inconsistent pad layer transfer due to not braking for what the pads were designed for?

There was a comment about someone who had switched to drilled/slotted I believe that didn't have issues with warping after the change. This brings up these questions, did they upgrade just the rotors and kept what pads they were using before, or were they using an upgraded pad that was included in a brake package with the drilled/slotted rotors? Where or through who did they buy this brake package from? People love to leave out info like this which confuses people now doesn't it.... Biased opinion to the core.
 

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'04 PSM WRX Premium
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Time for me to chime in.

I'm run stock replacements in good order, really really worn stock rotors and pads, Centric rotors up front with Hawk HPS pads, and now full Stoptech pads all around with Centric rotors.

I'll say this: We can debate which is better, slotter, drilled, blanks, etc, but when it comes down to it, you need tires to provide the grip the road with braking. I can tell you with RE-11A's, a 200 TW tire, my ABS just starts functioning on with hard braking and warm/hot pavement. No braking mods past good street pads, blanks, and a MC brace are needed for autocross and the street.

No, you won't get heat fade, no you won't stop better with slotted or drilled. No, a larger diameter rotor... sure, yes, you can see some differences in terms of heat soak on the track, or even just stopping force. But at the same token, you need the tires to keep up with that force.

If you're on Hoosiers or other race comps, then yes, larger diameter brakes will certainly help. Slotted or cross drilled, etc... I'm heard stories about people braking better, even with stock sized equipment, but it doesn't make sense. It may only be in 'feel', not actual braking performance.

... with that said, most braking upgrades are for feel, not really performance. At least on a street car.
 

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'01 2.5rs w/ V7 EJ207
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You need more than just tires.. You need better calipers, fluid, pads, lines, the perfect alignment, and suspension components. So much goes into making any braking system the most effective, it's not a simple as what kind of rotors you use. Just like getting a huge turbo and it needing supporting mods, so does your braking system.


I've had slotted and blank rotors, with FIGs suspension parts all around my Supra and IS300. Without the FIGs suspension components, I am certain that just pads and rotors would offer little difference.
 
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