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Old 12-09-2006, 01:19 PM   #1
Butt Dyno
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region: MAIC
Default The OFFICIAL Brake Upgrade / Big Brake Kit FAQ !

The OFFICIAL Brake Upgrade / Big Brake Kit FAQ

The goal is to explain the basics of brake upgrades. This used to be part of the “best coilover” thread but I felt it was worth splitting off so it could be discussed independently.

My brakes suck! How do I fix them?

They don't suck, I swear. They may not feel great, but that does not mean they are not working. Read the rest of the FAQ, but try to remember that pedal feel and stopping distance are not the same thing. You can do some mods that *may* help pedal feel (stainless lines, master cylinder brace) but those will not stop you any faster. Ultimately you are limited by the amount of traction your tires can provide. That is why the tires are one of the most important (and probably overlooked) part of your braking system.

If you are spending money upgrading your brakes and driving around on cheezy all season tires you will not stop as fast as the guy with stock brakes and good summer tires.

Anyway, read on

How do my brakes work?

If you’re curious and want to see diagrams and such, HowStuffWorks has descriptions for both disc brakes:

And drum brakes:

What are some common brake upgrades?

The most common brake upgrades are:
* brake pads
* brake lines
* brake rotors
* brake fluid
* brake calipers / big brake kits, including swapping to bigger rotors
* drum to disc conversion for the older cars

Some other modifications that people do:
* Master cylinder brace
* (suggestions?)

Why would I put on new brakepads?

For the non-STi owners, you would typically switch pads for a few reasons:
-You want better bite out of your brakes
-You want better modulation out of your brakes
-You want to increase your pads’ temperature range so they will not fade on you in hard driving. (Fade is discussed later)

For STi owners, the pads are pretty aggressive from the get-go. You still might want to upgrade them for the same reasons as above, but you might also want to “downgrade” them to pads that will dust less. A lot of people think that not having to clean off their wheels is more important than having aggressive pads.

What kinds of brake pads are out there?
1. Organic - Made of stuff like cellulose, which is like ground up cardboard! The cellulose is held together with a phenolic resin binder which is a heat resistant thermosetting resin. Pot handles and stuff like that is made of phenolics. Organic pads used to have asbestos to give better high temp properties but since asbestos is now a carcinogenic a no-no, kevlar, fiberglass and mineral fillers are now also used. Organic pads have a good coefficient of friction for a light pedal effort, work well at low temperatures and are very quite. They do not work so good for high performance use as they quickly wear, fade, oxidize and crumble. Organic pads are kind of old school and are common on cheap aftermarket replacement pads for older and sometimes new cars. These pads do not wear the rotors very much. Some cars have these as stock pads. Beware of these as they are worse than the stock pads. Suspect any cheap aftermarket pad. Organic pads are usually a light brown or tan in color.
2. Semi-Metallic - These have some powdered metal added to the mix to help stabilize the coefficient of friction at higher temperatures. Typically powdered Brass, iron or Bronze is added. Chopped brass or bronze wire is sometimes added to help give the pad more mechanical strength. Most stock pads on newer car are semi-metallic. Usually these pads are excellent for all-around use. They can run the gamut from very little metal to almost all metal. The more metal usually means better high temp properties, more noise, more rotor wear and less effective cold braking. Semi-Metallics run the gamut from light tan with metal flecks in them to a dark gray in color. The darker pads usually indicate a higher metal content.
3. Full metallic - These pads are made of sintered metal with very little binder. Sintered metal is powdered metal that is pressed into a mold at high temperatures until it becomes a more or less homogeneous piece. Pads of this type are pretty aggressive with ones made of brass, bronze or copper or a mix of metals being more streetable and ones using iron being more high temperature oriented. For very high temperature use, ceramic powder is added to the pad material. Axxiss Metal Matrix pads are streetable nearly full metallic pads that are made of brass and bronze powder with a resin binder. They are very streetable but I would not consider the other pads in this category as usable or even safe for street driving. Full metal pads are noisy, don’t grip when cold or wet and chew up rotors with annoying regularity. These pads make killer corrosive black brake dust so clean your rims frequently! I don’t think anyone on this list, even racers should consider anything more aggressive than the Metal Matrix or the new carbon pads. These pads are usually a dark gray to black and sometimes even copper-looking with a lustrous sheen.
4. Carbon - Carbon pads available to us mere mortals are not the amorphous carbon-carbon exotica that F-1 cars, the space shuttle and high performance jets use. They are not "carbon-fiber" either. Carbon pads that are available to us normal people are semi-metallic pads that have powdered carbon added to them to improve their high temperature properties. Personally I like most of these pads. For the most part, they have the cold friction of a good mild semi-metallic with the high temp properties of medium aggressive full metallic. Even the full race, high metal/carbon pads seem to have a fairly wide effective heat range. They for the most part are fairly good on the rotors also. Since they work so well over a broad range, carbon pads seem to have taken over the high-performance street pad market. The only drawback that these pads have is cost. They are pretty pricey. In my experience, they seem to wear a little faster than one might expect also. They also leave lots of black, corrosive, yucky, sticky, brake dust which is the main reason I will not use them on my street car. The full race carbon pads seem to eat rotors pretty well to. Carbon pads are a flat dark gray to black with a flinty look.
What tradeoffs should I expect with new pads? I want pads that will resist fade, not dust that much and be totally silent.

Cliff notes:
Originally Posted by Mark Avery View Post
There is no Santa Claus. There is no Easter Bunny. There is no good performance brake pad that does not make brake dust.
Every brake pad is a tradeoff of some variety. If you want better braking you are probably going to have to live with more noise and/or dust and/or rotor wear. This is probably my favorite NASIOC post on the subject, from [email protected] The orignal post is longer and worth reading; I clipped it to only include the part about brake pads:
Originally Posted by StopTech
The fact of the matter is that current friction technology cannot create a pad that:
1. Is totally silent. (Think of the reputation a noisy pad gets on a message board)
2. Doesn't dust. (Think of the reputation that a dusty pad gets on a message board)
3. Has good cold friction. (Think of the lawyers coming to take away your house because the pad you sold as a street pad didn't stop Joe's car first thing in the morning and he plowed into a mother pushing her twins across the street)
4. Is easy on rotors.
5. Leaves rotors perfectly smooth and mirror-polished.
6. Has good pad life.
7. Does not require the "customer service nightmare inducing" bed-in process.
8. Has a stable torque curve.
9. Fades gradually rather than torque falling off quickly(mid-stop).
10. Has good release and modulation characteristics.
11. Has an MOT that will allow aggressive track use.
12. Does not deposit uneven pad material when overheated.
13. Isn't too expensive.
14. Is available in your pad shape.
Why would I upgrade my brake lines?

The lines that come on your car are typically made of rubber, which allows for some flex. By installing stainless steel brake lines, you can eliminate some of that flex and have a firmer pedal.

When shopping for aftermarket brake lines, you should make sure that they are DOT approved. Ideally they will also be coated, just in case your brake lines ever come in contact with something, although that is not a cure-all.

Manufacturers of stainless lines include StopTech, Goodridge and STi.

I’ve done lots of brake upgrades, but my pedal still feels soft.

First, make sure you have a good bleed. Even some shops screw it up sometimes.

If you have a good bleed and you still feel that your pedal is soft, Mike Shields explains this phenomenon here, the dual stage brake booster:

You can switch to a single stage booster, but most people don’t bother. I’ve never driven a car configured that way so I can’t speak to how much better it is.

But basically, as Myles says here, you’ll never have that “the car is off” feel as long as you’re running a brake booster:
Originally Posted by RaceComp Engineering
As for getting the "when the car is off" feel,....LOL. forget it, or remove the brake booster and or get racing pedals. It will never feel that way, not to mention most people dont know how to modulate the brakes well enough without a brake booster and be fast or prevent lock up,.......................... Not unless you are a WKA champion and or Star Mazda regular and you live with no brake booster on a daily basis.
What are the best rotors?

Basically, for most people, rotors are rotors. I wouldn’t go nuts buying bling bling rotors unless they go with your big brake kit. They are chunks of metal that are going to slowly go away over time and that’s about it

There are some distinguishing features among rotors:
* two piece versus one piece: Two piece rotors have a lightweight hat in the middle that has the holes that mount to the hub, attached to an outer ring that contains the part of the rotor that the pad will grip. Here’s an example:

* Vented versus non vented: For the 02-05 WRX at least, the front rotors are vented but the rears are not. The 06 starts out better, with the 4-pot/2pot setup with vented rotors front and rear. The rears typically do less work, so this is OK. But if you are driving hard enough you may want to upgrade to vented rotors in the rear. (I think the new and old Legacy Turbo have vented rear rotors)

*Slotted versus drilled versus plain: Really there’s not much of a reason to use anything but solid. Slotted and drilled have tradeoffs:
* Might get a little bit better bite off of the slots/holes, but might wear pads faster as a result
* More prone to cracking around the slots/holes
* Slots might help a little bit in wet weather.
* Slotted/drilled are usually more expensive.

Basically, most of the problems that slotted/drilled rotors were built to solve are no longer problems. If you really want all the tech explaining why the drilled/slotted stuff is useless, check out this thread:

MaddMatt and Cobra make a compelling case for why drilled rotors are not a good idea In addition there is tons of valuable information about brakes in there. You may be thinking "but I have had drilled rotors and they haven't cracked". That's possible, but why risk it? Just for bling? If your brakes fail, you might end up somewhere you don't want to be.

I think my rotors are warped.

They're probably fine and just need a re-bedding:

It's possible to warp rotors, for instance if you overtorque or unevenly torque the lugnuts. But most cases where people have warped rotor feel, are not warped rotors.

Here's an excellent thread on the subject:

What kind of brake fluid should I use?

If you’re not tracking your car, you can stick with whatever the car has already. It’s really only during track events that you’ll see the temperatures that will cause your stock fluid to go out of its range.

Both the ATE Super Blue and Valvoline SynPower have gotten good reviews:

One nice thing about the Super Blue is that ATE also makes a Typ200 fluid that is the same as Super Blue, but in a gold color instead of blue. This makes it easy to tell when you’ve fully flushed the system from one to the other.

If you see fade with those, there are some more expensive options like Motul.

You should not use DOT5 brake fluid as it is silicon based and will not work right with your Subaru’s brakes. DOT 4 and DOT 5.1 are OK.

I just got new pads. What should I do to "brake" them in?

You need to brake... er... break in your new pads to build a layer of pad material onto the rotor. There are more details here:

The basic jist is: You find a place with very straight roads and no traffic. You do a series of stops from a high speed to a low speed - maybe 60 mph to 10 mph nine or ten times. Then, let the pads cool - i.e. drive on the highway for a while without touching them (if possible) or at least without leaving your foot planted on them (i.e. don't stop on a hill). StopTech recommends doing this cycle twice for street performance pads. I have never done it more than once and it's always worked out OK. Your mileage may vary. It's pretty hard to find a safe spot to do this, and as always, NASIOC does not condone anything illegal or dangerous. Your best bet is to pop a Red Bull at 2 AM and do it while no one else is on the road or something along those lines.
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Last edited by Butt Dyno; 06-14-2008 at 09:01 AM.
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Old 12-09-2006, 01:19 PM   #2
Butt Dyno
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region: MAIC

Part 2: Big brake kits and other meta-issues.

Do I need to upgrade my brakes?

In general - your stock brakes are probably pretty good (depending on which car you start with). I quote Gary Sheehan a lot in this FAQ. He RACED, yes RACED, a WRX on the stock calipers in NASA's US Touring Car Challenge - basically NASA's equivalent of SCCA's World Challenge. Serious touring car racing. He ran on the stock calipers for an entire season. And did well. Consider this when you are thinking about whether or not you need to upgrade your brakes. (More info: http://forums.nasioc.com/forums/showthread.php?t=197590)

Ultimately he and his team went with Stoptechs - not because they were seeing fade on that setup, but because the heat generated from it was causing unnecessary wear elsewhere. (And again... they were RACING... not doing track days, not autocrossing, and not doing "spirited driving".)

If you are doing anything other than tracking the car, or driving like an asshat on public roads, you likely do not need a big brake kit or anything close to it. If you are fading your brakes driving on the street, slow the **** down.

What are some reasons people upgrade their brakes?

1. They want to decrease stopping distance.
2. They want their brakes to handle heat well and not fade (i.e. track use)
3. They want their car to brake "flatter"
4. They want their brakes to look cool
5. They want to reduce unsprung weight.

Let's look at those reasons.

1. Decreasing stopping distance

How can I shorten stopping distance? What's the best bang for buck way?

This one is easy - TIRES! As Stoptech so elegantly says:
1) The brakes don't stop the vehicle - the tires do. The brakes slow the rotation of the wheels and tires. This means that braking distance measured on a single stop from a highway legal speed or higher is almost totally dependent upon the stopping ability of the tires in use - which, in the case of aftermarket advertising, may or may not be the ones originally fitted to the car by the OE manufacturer.
If you are dropping big $$ on brakes while running all season tires, you are wasting your money!

"I don't believe you... I installed cross drilled rotors and my car stops on a DIME now!"

Your butt dyno may be tricking you.

Originally Posted by GarySheehan
If you added front bias because the pistons are too big, it will definitely FEEL like it's braking harder, because the nose will dive down more. If the pistons are sized correctly, the simple fact that you've got much better pedal feel can make it feel like you're stopping considerably harder.

Consider this. Decreasing stopping distance from 60-0mph by 6-10 feet with a brake upgrade is considered a MAJOR improvement over stock in the braking industry. I'm not sure that anyone can feel that difference. So when people say their brakes stop so much harder than stock and they haven't upgraded tires, the first thing I think of is too much front bias.

The only way to significantly decrease your stopping distance is to put stickier tires on the car or drastically increase downforce. Period. Anyone that tells you otherwise is is lying to you or doesn't know what they are talking about.

Sheehan Motor Racing
Size changed for emphasis

I don't believe you... I have a BBK not just pads... I swear I stop like 50 feet sooner!

Originally Posted by GarySheehan

I'm inclined to think that your 50 foot drop in braking distance is more a factor of driver improvement or driver confidence rather than the actual effectiveness of the brakes. As long as the brakes are within the temp range of the pad, they will both stop the car very similarly.

I raced for a full year on the stock rotors and calipers. We had them set up where they would not fade. Switching to Stoptech's made my life easier because they are more consistent, have a better feel and run at lower temps, thus not ruining everything around the braking system. But they did not drastically decrease my stopping distance. Probably a few feet.

I could see you losing 50 feet of stopping distance if you were experiencing pad fade with the stock system, but you can't compare the two. If you used a hot pad and a hot fluid in the stock system, they wouldn't fade and then you could make that comparison.
How ELSE can I decrease stopping distance?

Here is a pretty good thread:

2. Reducing brake fade

What is brake fade?

Brake fade occurs when your brake system is put into a temperature range that it was not designed for. This can happen if you take your car to a track event without upgrading the brake pads and brake fluid. The result is that you will push the brake pedal, but the car won’t slow down, which is quite unpleasant

There are three types of brake fade:

Pad fade: your pads are designed to work inside of a certain temperature range. If you get them too hot you can get them outside of that range, especially if they are near the end of their life. You resolve this in two ways: 1) driving within the limits of your pads (duh) or 2) installing pads with a higher temperature range.

Green fade: If you do not bed your pads in, they will not grip like you expect them to. This is easily fixed. Bed in your pads!

Fluid fade: Like pads, brake fluid has a temperature range it is comfortable operating in. If your fluid is not up to the task, it can boil, which introduces air bubbles into the brake system. This results in a soft pedal and can also be quite scary. Fortunately, better fluid is cheap.

"I'm not an asshat, I track my car, but I see fade. What should I do?"

Make sure you have pads that are track-worthy. There are basically three categories of brake pads:
-street-only pads: won't hold up to a track day. Either don't try, or drive like a chicken on the straights
-street/track pads: you can track these, but you will have to deal with the tradeoffs - likely noise and dust.
-track-only pads: you don't want to daily drive these, as the noise and dust will likely annoy you. They may also eat your rotors prematurely.

Make sure you also have a brake fluid that won't boil easily.

Finally, if you still see fade, congratulations! You're probably working the car pretty hard. It's time to start looking into vented rotors and big brake kits.

You can also try brake ducts. Some vendors (i.e. RaceComp Engineering) make some, and some people have made their own.

What else should I know about picking pads for track use?

A thread full of good advice, especially Todd TCE's post, is here:

3. Braking "flatter"

When I hit the brakes, the nose of the car dives down pretty significantly. Can I fix this?

Most Imprezas come with a fairly significant front brake bias from the factory. For a discussion of brake bias, check out this article on StopTech's website:

There are a few ways to make the car more "flat" while braking:
-Suspension mods. Making your suspension stiffer (i.e. the springs) (and lower - right?) will make the car dive less.
-Reduce front brake torque
-Increase rear brake torque

OK, I've got a stiffer suspension. I'm decreasing weight transfer under braking now, right?


... the amount of weight transfer is not altered by springs, shocks, anti-roll bars, etc. Weight transfer is a result of inertia and momentum. These suspension components cannot change that. What these components can do is impact how much the suspension moves in response to the load change, and how quickly the load transfers to the tire contact patches.

The amount of weight transfer is dominated by the vehicle's weight, location of the center of gravity, wheelbase, and track, and the amount of force applied during braking, accelerating, and cornering.
It goes on to say that suspension mods can change the *rate* of weight transfer, and help maintain the appropriate contact patches and all that

How can I change brake torque?

Legacy777 has done a bunch of work on this subject.

His Excel spreadsheet for calculating brake torque is here:

Some of the variables that you can easily control are:

* Pad coefficient. If you want more rear bias, put a more aggressive pad in the rear than the front, and vice versa.

* Rotor size. This changes the effective diameter of the rotor. Bigger rotors = grab the rotor further out from the center = more effective torque.

* The "H6" upgrade is very popular among Impreza owners because it's so damn cheap and has a noticeable impact on the car's bias. For the 2.5RS's and the 02-05 WRX's, the stock rear calipers can be used with a larger rotor from the H6 Legacy, and a different caliper bracket to move the stock rear caliper further out to accomodate the bigger rotor. You definitely need the OEM caliper bracket, but you can choose from several 290x10 rotors if you want slots or something.

* Unabomber's guide to the H6 upgrade is here: http://forums.nasioc.com/forums/showthread.php?t=522006

* A list of non-Subaru H6 sized rotors is here: http://forums.nasioc.com/forums/showthread.php?t=562057

* Piston area. The visual size of the calipers has NOTHING to do with how much torque they generate. The crappy looking two pots from the 02-05 WRX have more piston area than the 4-pots on the 06 WRX or the StopTech kit for the 02-05 WRX. If the 4-pots are placed on an 02-05 WRX they will reduce the front piston area and thus decrease front brake torque.

4. Making the brakes look cool

I saw this sweet BBK from some cool sounding Japanese company. I want to put it on my car to impress my friends. Should I?

What you should never do is compromise your car's safety for looks. I didn't realize how bad some of the BBK's on the market were until I saw this:

Now - admittedly this is StopTech's website. But StopTech doesn't make any outrageous claims. The stock RSX in that comparison was on Michelin Pilot MXM4's - an all season tire. It did 60-0 in 132 feet. Of the two StopTech shod cars, one was on Hoosiers (very sticky) and one was on Advan A032R's (also very sticky). So you'd expect them to stop noticeably shorter than the stock car on all seasons.

But the terrifying thing about that comparison is how bad some of those high dollar kits are. A Ford Expedition stops 60-0 in 140 feet, 8 feet slower than our stock RSX (see http://autos.yahoo.com/ford_expediti...4-performance/)

-The Brembo kit, on sticky Advan 048's, was a foot slower to stop than the stock RSX.
-The Wilwood kit, on Nitto NT01's (race tires), was 11 feet slower to stop than the stock RSX, and equivalent to the Ford Expedition.
-The Project Mu kit, on the same Hoosiers that the StopTechs stopped in 110 feet with, stopped at 171 feet. To put that into clearer terms, if they were 30 feet behind the Expedition at 60 mph, and both the Expedition and the Project Mu RSX hit their brakes at the same time, the RSX would still rear end the Expedition. That's freaking ridiculous! And how many of you leave 30 feet between you and the car in front of you at 60 mph?

There are other variables - wheel alignment for instance, maybe some of the cars were broken - but it's a pretty scary looking test.

Cliff notes: make sure your bling is well-engineered bling.

5. Reducing unsprung weight

Will my BBK be lighter or heavier than stock?

Here's a list:

"what else should I read about brakes"

There are some great articles on stoptech.com: http://www.stoptech.com/technical/

I hope this is helpful!

Last edited by Butt Dyno; 12-21-2008 at 02:02 AM.
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Old 12-09-2006, 01:20 PM   #3
Butt Dyno
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region: MAIC

I just bought new pads. Do I need to buy new rotors or have my rotors turned?
I just bought new rotors. Do I need to buy new pads?

This comes up somewhat frequently. Some folks have asserted that you need to buy them in pairs. So I sent this question to some of the NASIOC brake experts:
Originally Posted by ButtDyno
I've always wondered about this and I would like to add it to the brake FAQ. I have always gone by the rule "whenever you swap anything (pads or rotors), bed it in afterwards" and it's worked out fine for me - i.e. I have not always bought in sets. I would be curious to know what you guys think.
I got three replies. There is some nuance here so I don't want to add cliff notes

1. Eric @ StopTech:
Originally Posted by ESmooth
There's definitely no need to get new pads and rotors at the same time.

If you are getting new rotors only and your existing pads have good volume remaining, a bed in procedure is all that is needed to lay down a good transfer layer of pad marterial.

If you are putting new pads of the same compound on used rotors, a bed-in cycle is again all that is needed in order to put the new pads through green fade and to refresh the existing transfer layer.

If you are putting new pads on old rotors that were used with a different compound, its best to drive around normally for a few days or a week in order to clean off the pad transfer layer of whatever was being previously used. After the old material is gone, a normal bed-in cyle should be done to establish a transfer layer of the new pad material onto the rotor face and to put the new pads through green fade.

Some compounds dont play well with each other and trying to bed one compound in over another can lead to vibrations and poor performance. If you have some race pads for your calipers, its a good idea to drive on those for a day or so between pad changes since they are more abrasive and will make the clean up of the rotors go that much quicker and reduce the chances of contaminating the new pads with the old material.

Feel free to use that however you need it for the FAQ page.
2. Ken @ WRXBrakes:
Originally Posted by WRXBrakes
Well - as usual it's not simple.

Assuming pads and rotors are still flat and not tapered then used pads are good to bed new rotors with. They transfer material more evenly leading to less instances of pulsing/judder. They should be of the same or similar type for best results i.e. trying to bed in Carbotech ceramic pads after OEM Brembo semi-metallics can be problematic.

The chemistry at the interface is sensitive to a lot of things - but usually you can re-bed old pads to new rotors and vice-versa.

Another example is trying to bed in street pads after race pads - can be tough.

It's usually somewhat visible - smearing on the rotor surface etc.
3. Todd @ TCE:
Personally, I've not had any issues with old pads on new rotors or new pads on old rotors. Not like I toss out a set of race car rotors just because the car needs pads...I wish! lol I could make some money on that one.

I usually lightly sand the pads down and put them in if they are used and let 'er rip.
Might add that when you do change pads on old rotors however that you may want to consult the new supplier as to their suggestion for rotor prep also. I have seen where moving from a long time PFC use to another brand can cause issues. They put down a lot of carbon transfer and the new pads slip right over the surface if you don't scuff them when the new pads are installed. In short, I'd always suggest a hand sanding if you change compounds or brands.

Last edited by Butt Dyno; 01-23-2008 at 11:39 AM.
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Old 12-09-2006, 01:20 PM   #4
Butt Dyno
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Join Date: Apr 2002
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How do I swap from drums to discs?

Upgrading Rear Brankes '03 TS - Drum to Disc

I have a late 2002/early 2003 WRX. What pads do I need?

StopTech has a handy guide here:

Drilled rotors *must* be good for track use! Porsche/BMW/Lamborghini use them on their cars!

Here's some things I've found from the major brake manufacturers:

Drilled or cross-drilled rotors : Discs that have been drilled through with a non-intersecting pattern of radial holes. The objects are to provide a number of paths to get rid of the boundary layer of out gassed volatiles and incandescent particles of friction material and to increase "bite" through the provision of many leading edges. The advent of carbon metallic friction materials with their increased temperatures and thermal shock characteristics ended the day of the drilled disc in professional racing. They are still seen (mainly as cosmetic items) on motorbikes and some road going sports cars. Typically in original equipment road car applications these holes are cast then finished machined to provide the best possible conditions by which to resist cracking in use. But they will crack eventually under the circumstances described in another section (see Cracking). Properly designed, drilled discs tend to operate cooler than non-drilled ventilated discs of the same design due the higher flow rates through the vents from the supplemental inlets and increased surface area in the hole. That's right, inlets. The flow is into the hole and out through the vent to the OD of the disc. If discs are to be drilled, the external edges of the holes must be chamfered (or, better yet, radiused) and should also be peened.
We have countless street cars and full race cars running our products on the track. StopTech never recommends drilled rotors to customers who plan to track their car. All of our testing and data collection has shown that drilled rotors do not perform as well as slotted or plain rotors at the track. The drilled rotors crack more easily, they develop terrible concentric grooves, and just don't last as long.

We've gone through TUV approval on a number of our applications in Germany. This testing involves putting some severe strain and endurance testing on rotors. The results are always the same...the drilled rotors don't take the same level of punishment. We just don't view the benefit of a bit more pad bite and water evacuation as worth the tradeoffs for most of our customers.
In years past, cross-drilling and/or slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads began to break down at extreme temperatures. This condition is often referred to as "green pad fade" or "outgassing". When it does occur, the driver still has a good firm brake pedal, but simply little or no friction. Since this normally happens only at temperatures witnessed in racing, this can be very exciting! However, with today´s race pad technology, “outgassing” is no longer much of a concern. When shopping for races pads, or even ultra high performance road pads, look for the phrases, "dynamic surface treatment", "race ready", and/or, "pre-burnished". When these or similar statements are made by the pad manufacturer, the pad in question will likely have little or no problem with “outgassing”. Ironically more pedestrian pads used on most streetcars will still exhibit “outgassing”, but only when used at temperatures normally only encountered on the racetrack. Although cross-drilling and/or slotting will provide a welcome path to expend any gasses when and if they develop, it is primarily a visual enhancement behind today’s often wide-open wheel designs. Cross-drilling offers the greatest gas relief pathway, but creates potential "stress risers" from which cracks can occur. Baer´s rotors are cast with cross-drilling in mind, from the material specified, to curved vanes, behind which the holes are placed to minimize potential crack migration. Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer’s offerings.
Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity.

Slots or grooves in rotor faces are partly a carryover from the days of asbestos pads. Asbestos and other organic pads were prone to "glazing" and the slots tended to help "scrape or de-glaze" them. Drilling and slotting rotors has become popular in street applications for their pure aesthetic value. Wilwood has a large selection of drilled and slotted rotors for a wide range of applications.
Caution on drilled rotors: There is a common mis-perception that rotors are drilled to improve cooling. The reduced mass of a drilled rotor will dissipate its retained heat quicker, but it also builds up heat at a much faster rate. The decision to use drilled rotors should be solely based on the merits of the lower rotating and unsprung weight, and not for improved cooling. It is not wise to use drilled rotors in sustained high heat on hard braking tracks unless the team budget affords a high frequency of rotor and brake pad replacement.
AP Racing:
Drilled discs.

1. Lighter weight than a grooved equivalent

2. Good brake bite due to:

A forcing pad material into the holes

B increased braking surface (many leading edges in theory)

3. allowing gases formed during the braking cycle to escape from the disc braking face.


Discs can be prone to cracking unless care taken when bedding in

The use of hard race pads(high friction level) can cause cracking giving the disc a limited life.

You will find today that most forms of car motor sport will use grooved discs.
Anyhoo - I'd happily admit that I'm not technical enough to speak to all the intricacies of heat transfer as long as everyone else admits that drilled rotors are not a good idea on a track car

But if you cast the holes in place, it should be better than drilling them, right?

No From Brembo:
Are discs with cast-in-place holes better than cross-drilled discs?

Brembo has extensively studied and tested cross-drilling versus casting the holes in place and found no significant effect on performance or durability.

Last edited by Butt Dyno; 01-22-2009 at 07:04 PM.
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Old 12-11-2006, 01:08 PM   #5
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wow~ Lots of Infos here. These are exactly what I was looking! Big thumps up for you, buttdyno. so which BBk is the best?? lol jp~

And how come this is not a sticky??
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Old 12-11-2006, 03:28 PM   #6
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Originally Posted by TJRCS View Post
wow~ Lots of Infos here. These are exactly what I was looking! Big thumps up for you, buttdyno. so which BBk is the best?? lol jp~

And how come this is not a sticky??
It's in the "faqs and threads of note" but I'll sticky this and the swaybar one for a couple weeks to get people's feedback.
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Old 12-16-2006, 06:35 PM   #7
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nice One minor correction-"the WRX has vented front brakes and solid rears"- true w/ the USDM until 06

As one who has tracked his car a fair amount on oe size rotors- our cars are heavy and I can't emphasize what a difference ducting can make in keeping things "relatively" cooler (they still get smoking hot!)
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Old 12-17-2006, 05:51 PM   #8
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Originally Posted by BIGSKYWRX View Post
nice One minor correction-"the WRX has vented front brakes and solid rears"- true w/ the USDM until 06
Fixed Thanks!
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Old 01-08-2007, 03:54 PM   #9
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Awesome info and it should definitely be a sticky. My STI's pads and rotors are shot right now. Looking at the cost of replacing them I was like why dont I upgrade while I am at it. Now I am asking my self why dont I put that money some where else in the car! I still have a lot more to research and reading to do but this was beyound helpful. Thanks BD!
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Old 01-10-2007, 12:11 AM   #10
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trying to find info on the 4 pot 2006+ swap.
I hear they just bolt on... is this true or do I need some sort of caliper bracket?
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Old 01-12-2007, 07:48 PM   #11
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I really love getting quality information like this!!!

I just did my "big brake upgrade" on my 2000 RS

new hawk hps pads
stainless lines
turned existing rotors
ATE super blue

$300.00 total

ohh forgot the main component, Tires
Falken ziex 512 vr 16

$500.00 installed
my butt dyno is VERY pleased
where can i get the master cylinder brace
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Old 01-14-2007, 02:52 PM   #12
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hmmm sr-30+640cc=?
I has teh Endless BBK.


Man, only got to the 2nd post while reading & I just had to say 'thanks'. So, thanks!!
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Old 01-21-2007, 01:18 PM   #13
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Question heat-related problems. 2piece aluminum?

Buttdyno wrote that stock brakes were used in racing applications:
"Ultimately he [Sheehan]and his team went with Stoptechs - not because they were seeing fade on that setup, but because the heat generated from it was causing unnecessary wear elsewhere. (And again... they were RACING... not doing track days, not autocrossing, and not doing "spirited driving".)"
I agree that stock brakes can be set up to work without fade, and eventually the excess heat will damage something else.
The first sign of damage to other components that I have seen from track events in my own 2002 WRX, and friends', has been piston dust boots melting and ripping. No feeling of fade while all this was happening, but the design of the stock brakes do not sweat off the heat very well.
***I have heard that a 2 piece with aluminum hats will not carry as much heat toward the hub. Is that true?***
Also my 2 cents on cross-drilled rotors for the 02 WRX is DONT BUT THEM. They sound like a good idea, degassing and all that stuff. I paid big bucks on some Brembo cross-drilled for my stock 02 WRX, and went to the track with nice Carbotch Panther pads and Toyo RA-1s. The Brembos did fine on the track, but cracked in the paddocks while cooling. The Cracks were so big you could hear it slapping the pad when the car rolled. I couldnt even drive the car until I replaced the rotors (luckily i brought some).
My solid rotors have always been dependable (all 4 sets), and only had to be replaced for minimum thickness reasons after many track days. Thankfully they are cheap. And it is easier to replace them at $70 for 8-10 track days versus $1500 for a big brake kit ( plus another $1500 for new 17"s to go over big brakes)

Last edited by X-VWGLX; 01-21-2007 at 02:07 PM. Reason: spelling
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Old 01-22-2007, 11:46 AM   #14
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wow so i should deffinately keep my wrx 2pots?? opposed to a oem 4pot upgrade and stoptech for the 02-04wrx.
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Old 01-23-2007, 12:50 PM   #15
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Wink not really...

Originally Posted by drrice View Post
wow so i should deffinately keep my wrx 2pots?? opposed to a oem 4pot upgrade and stoptech for the 02-04wrx.
I have heard from people who have tried Stoptechs that they work great, maybe even better than the stock setup in the STi (under track conditions of constant high heat). I dont personally know, just parroting what I've heard.
I think the Stoptechs would be naturally more reliable at the track than our 2pots, probably no reason to buy them unless you frequent the track.
Here is what I do know: A good set of agressive (track) pads are all you need to make the stock brakes feel like a big brake kit. I loved my Carbotech Bobcats on the street (not for track use). longevity of this setup at the track...not so good, but cheap and easy to keep going.
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Old 01-24-2007, 08:08 PM   #16
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It would be nice if there was some information on bedding pads in here. Add that to the FAQ!
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Old 01-25-2007, 05:23 AM   #17
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Originally Posted by keirnna View Post
It would be nice if there was some information on bedding pads in here. Add that to the FAQ!
I was under the normal break in of pads. 30-30-30. 30mph-30ft stopping distance- wait another 30 seconds. Or something like that, others just go 30-40mph to a complete stop under hard braking

I had EBC yellow's now i am wondering if I should go back to them, carbotechs, or hawks. I understand all are greatand i did love the EBC's.
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Old 01-25-2007, 02:39 PM   #18
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At the Track

Originally Posted by keirnna View Post
It would be nice if there was some information on bedding pads in here. Add that to the FAQ!
to bed pads you want to get them really hot, then allow them to completely cool.
the best thing to do is brake rapidly form 60 down to almost 0. Repeat 3-4 times until they really stink. Now park the car. Allow them to cool for at lest 30 min. U R done.
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Old 02-21-2007, 09:38 PM   #19
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Thank you guys! Informative thread.

Last edited by Butt Dyno; 02-22-2007 at 09:14 AM. Reason: despamifying.
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Old 02-25-2007, 04:45 PM   #20
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Wow. I read all those white pages at StopTech.com. Great info! It's probably going to save me a ton of cash.
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Old 04-13-2007, 07:29 PM   #21
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Bump for folks who haven't seen it yet. Feedback is always welcome.
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Old 04-23-2007, 10:17 PM   #22
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Very informative for those who know little (raises hand) about braking and what is affected and when.

I came here looking for a DIY on BBK, and am now more informed. However, I still have a question in my mind...

Can I put 2005 WRX brakes/rotors/calipers/mounting brackets fit on my 1996 OBS with rear discs?
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Old 05-17-2007, 05:04 PM   #23
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Originally Posted by X-VWGLX View Post
to bed pads you want to get them really hot, then allow them to completely cool.
the best thing to do is brake rapidly form 60 down to almost 0. Repeat 3-4 times until they really stink. Now park the car. Allow them to cool for at lest 30 min. U R done.
It looks like on the Stoptech website that their procedure for a proper bed in is a little different/more aggressive.

They suggest you do 10 times a 60 MPH to 10 MPH hard braking to lock up your tires/abs "(about 80 to 90% of the deceleration required to lock up the brakes and/or to engage the ABS)," from the stoptech website. After this you want to let the car cool by driving at a good speed without braking to a stop but applying the brakes? This part is a little confusing..

After cooling, you want to do another 10 times 60-10 hard braking and let it cool after that.


(the link is also on top of the page)

My question is, what do they mean by "The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances, without bringing it to a complete stop with the brakes still applied."

Are we cruising on the freeway while left foot braking or are we just driving normally while braking from time to time?
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Old 05-17-2007, 05:20 PM   #24
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I think you just need to break up the sentence differently.

I think you're looking at it like this:
(The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances), (without bringing it to a complete stop) (with the brakes still applied).

But I think the intent is:

(The system should then be allowed to cool, by driving the vehicle at the highest safe speed for the circumstances), (without bringing it to a complete stop with the brakes still applied).

As in - you can hit the brakes if you have to but don't sit at a stop light with your foot holding the pads against the rotors.

I'm sure ESmooth will check in tho, now that the StopTech bat-signal has been fired into the sky.

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Old 06-03-2007, 01:00 AM   #25
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Wink Some fine break upgrade advice

If you are fading your brakes driving on the street, slow the **** down.
LOL'd Mr. ButtDyno! THXS for that.
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