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The Silverback Mod
05 Black OBS
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Discussion Starter #122 (Edited)
remember who you are arguing with, i'm not the guy that said you will die on the street in them
Oops! My bad. I did get ya mixed with noTe.

Nobody "NEEDS" upgraded brakes for the street. If you DO push your car hard on the road and/or do occasional track/autocross days you SHOULD upgrade your brakes to the best of your budget. Simple logical truth...

That's all this thread was trying to state at the beginning and I part with that thought.
 

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'98 2.5 RS
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763 Posts
my $.02 on the subject: from what ive read on the subject slotted and drilled rotors were used back in the day to dissipate gas build up between the rotor and the pad. however with newer pad compounds this is no longer necessary. i dont remember the details of this argument now, but the supporting evidence was persuasive.

furthermore, at the end of the day a brake rotor is nothing more than a heat sink. the more capacity a heat sink has to absorb heat the better it will do its job. by drilling holes in the rotor you are reducing the effective surface area (capacity to absorb heat) of the rotor and building up more heat on less surface area. this will often lead to cracking around the holes (ive seen it and done it myself). the same applies to slotted. you are removing metal from the rotor that would otherwise be absorbing heat.
 

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2000 BRP 2.5 RS Sedan
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198 Posts
furthermore, at the end of the day a brake rotor is nothing more than a heat sink. the more capacity a heat sink has to absorb heat the better it will do its job. by drilling holes in the rotor you are reducing the effective surface area (capacity to absorb heat) of the rotor and building up more heat on less surface area. this will often lead to cracking around the holes (ive seen it and done it myself). the same applies to slotted. you are removing metal from the rotor that would otherwise be absorbing heat.
False. By drilling/casting holes in a rotor, you are increasing the surface area, decreasing the mass of the heatsink. So now the rotor has slightly less mass, and has slightly less surface area in contact with the pad, but more surface area in total to cool itself quicker.

More Surface area=Good thing. That's why 2.5 guys upgrade to H6 rear disks on the cheap, because they are vented, vastly increasing their surface area. More surface area, the quicker the disk can cool down.

*Just realized the last post was in April. Sorry.

If you take the heat sink concept and move it to the engine bay, that's why car radiators aren't just solid blocks. The surface area of a radiator is HUGE in relation to it's dimensions, allowing rapid heat transfer
 

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turbocharged mayhem
MBP 03 wrx wagon
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More Surface area=Good thing. That's why 2.5 guys upgrade to H6 rear disks on the cheap, because they are vented, vastly increasing their surface area. More surface area, the quicker the disk can cool down.

H6 rear rotors are not vented, they are solid. Most people run them to increase the rear brake bias of the car.

My cousin ran drilled and slotted rotors on the front of his car, some of the holes developed cracks.
 

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AYVI Motorsports
White 98 Impreza/06WRX
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440 Posts
^^ H6 rotors improve rear braking power because they are BIGGER DIAMETER so the caliper can apply more torque with the same braking force. Another way of looking at it is to get the same braking you apply less force and therefore build less heat into a rotor that has more mass anyway.

I would not say drilling "Vastly increases surface area" and how much air do you think flows laterally through the disk as is it spinning ... hardly any. And in the case of vented rotors they cool by sucking air in close to the center and venting it out radially. Having rotors drilled would do nothing but hinder this.

I'm sure this was summed up a long time ago but solid rotors are better then drilled ones. If you want to spend money on nice rotors that will actually improve your braking get two piece ones. In either case the difference will be negligible on the street and if you want to waste your money on rotors cast with holes in them go ahead.

/thread.
 

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2012 Audi S4
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its really up to the driver what gives them the best bite for their driving style.

if you drill holes you ARE reducing the surface are and therefore reducing the friction/braking force applied. however with these added holes air can move quicker in and around the rotor cooling it quicker and removing heat from the rotor itself.

it is my knowledge that if cracks form that they are caused my improper casting techniquies that leave residual stresses in the part (rotor). Without a proper annealing process after the part has been cast these stresses will remain and can lead to cracking. annealing doesnt assure that there will be no internal stresses, but definitely reduces it. automakers like MB and Porsche know this and apply the proper means the reduce the likelyhood or cracking in their drilled rotors. cheap drilled rotors will crack, expensive rotots may crack, its all about how well your parts were made that particular day lol
 

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The Silverback Mod
05 Black OBS
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Discussion Starter #128 (Edited)
Automakers like MB and Porsche know this and apply the proper means the reduce the likelyhood or cracking in their drilled rotors.
Thank you for your accurate perception. Do you really think the best manufactures of cars in the world simply put the 'drilled' (which they ARE NOT) rotors on their highest performance cars for "bling" and not 'performance' at the detriment of the owner/driver and the lawsuits certain to come from their poor braking decisions??? :bonk:
 

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If you guys really wanna know about brakes, we should all talk to Toyota. They got it going on. :)
 

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AYVI Motorsports
White 98 Impreza/06WRX
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if you drill holes you ARE reducing the surface are and therefore reducing the friction/braking force applied. however with these added holes air can move quicker in and around the rotor cooling it quicker and removing heat from the rotor itself.
ha ha did you read what I said ... how much air do you think is going to move through those holes with the rotor spinning.... hardly any
And yes it will still aid cooling but it is literally nothing compared to the heat removed by air moving through the rotor's VENTS

Thank you for your accurate perception. Do you really think the best manufactures of cars in the world simply put the 'drilled' (which they ARE NOT) rotors on their highest performance cars for "bling" and not 'performance' at the detriment of the owner/driver and the lawsuits certain to come from their poor braking decisions??? :bonk:
I know they are not literally drilled, and do not believe that they are in danger of breaking, but those "high performance" car companies actually are not making race cars they are SELLING cars and brake calipers that look cool are MARKETABLE. Its not that they will perform noticeably worse then non drilled ones but they are more expensive to make for no benefit. If you look at most Porsche race cars they take those rotors with holes in them off, and put on either blank or slotted 2 piece rotors.
 

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1993 impreza l agean blue.
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blank rotors better than cross drilled/slotted

hey, I came across this when looking for new rotors to buy.

WHY Blank rotors are better than cross drilled and/or slotted - Honda-Tech


I read this, along with some other articles about the subject, but i have had xdrilled rotors from Powertop for almost 3 yrs now, changing brake pads twice, and haven't had any problems from them. i have noticed they've been wearing down for about 2 months now (starting to show some lip around the outside). just wondering what others experiances with xdrilled/slotted rotors are, and if you prefer blanks over them.

thanks
 

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96 GF4 " Bruiser"
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for a street car that doesnt see a huge ammount of heat, drilled/slotted rotors are NOT for you. they provide LESS braking surface and chew on your pad more. Stick with blanks
 

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1993 impreza l agean blue.
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every car i have had, had blanks on them including my 93L when i got it, and they all start to warp fast, even after breaking them in the proper way. the reason i would get another set of these is to prevent warping and having to buy rotors and pads as often. and as i said in the op i have changed pads twice in 3 yrs (they are not ebc's or anything special), idk too many people that have been able to do that. no i don't do a lot of heavy braking but everyonce in a while everyone does when idiots are in front of you, and most people i know on their dd cars they have warped rotors within the first yr of having them put on, which causes them to have to be resurfaced, buy new pads and some cases new tires bc of the shaking
 

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I had crossed drilled and slot a few years back. I've use the car for mainly autox/HPDE and it start showing some cracked on the drilled. And this was on a 21xx lbs Civic.

Never going to used crossed drilled slot ever again. Blanks only now.
 

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2012 Audi S4
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its all depends what sorta pads your are putting on your car? properly bleeding the fluid? Are you hard on the brakes? Blanks rotors are fine for a DD, however i do believe there are some advantages to getting simple slotted rotors over them. ive had slotted rotors on my car with the same pads (portfield) for almost 4 years now (60,000kms) and no evidence of pitting (rotors DO NOT WARP, they pitt which is a form of corrosion). And after a recent OOP inspection all my pads and rotors have worn the same within +/-0.2mm of eachother, not bad id say.

What blank rotors are you buying? Over the counter ones at an general automotive parts store or OEM or EBC?
 

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good drilled rotors should not crack. drilling after casting produced interal stresses and if not annealed then the formation of cracks is inevitable. this is usually seen on cheaper rotors, if they are as cheap as a blank stay away.

Mercs and Porsche use drilled rotors on almost all their cars for street use and mild track use. something must be working for them...
 

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1993 impreza l agean blue.
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like in the drilled rotor crack google search, any rotor can crack (blank,xdrilled or slotted). I have had mine 3 yrs and check them every 3-6 months for any cracks or chips, I've used the evolution pads that came with them and haven't had problems, I will probably get some more powerstop rotors, I looked at the brembo blanks but I'll prob stick with the powerstops, but haven't decided on pads yet.
 

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96 GF4 " Bruiser"
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3,540 Posts
yeah most cheap rotors are annealed ( hardened) then slotted and drilled. Good quality rotors ( DBA brembo stoptech carbotech etc) are machined FIRST then hardened. I had some D/S rotors on my ae86 and under just auto-x use they started cracking causing a intermittent grabbiness, making smooth powerful stops impossible
 

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The Silverback Mod
05 Black OBS
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Discussion Starter #140
Oh my God! How many threads do you think are here on this same subject??? 'Drilled' rotors are almost non-existant these days they are beveled and cast. Do you really think the worlds fastest production cars would be running them if there were issues. How many would Porsche, Mercedes, BMW, Jaguar, Lambo, Ford et al have to replace under warranty if this was the case??? For the sake of their fiscal life they would go to 'blanks' if they were an issue.

Since my 1st high performance car in 1973, I have run 'drilled', slotted or dimpled rotors with out a single failure or issue.

Worry about the upcoming 'rapture' instead, it will be more productive then this tired debate!
 
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