FAQ: Brake Rotors and Pads

I installed my set of HPS pads and powerslots today. i almost forgot what it was like to have quality pads after those cheapo ceramic ones that i replaced.
shot of the rotor next to a quarter...


Got heat?
here is a shot of the rotor after breaking in the pads. i got them so hot the paint on the edge bubbled up and flaked off. also they were smoking so much people were looking at me like i was spinning the tires
needless to say they stop like a beast as always, but i'm hoping these will run cooler and not heat crack like my last 2 sets did. the new rims really help in cool down too.

maybe a dumb question, but the one with the "L" goes on the driver side right? left/right is relative to how you look at the car, but i always thought the driver is on the left side.
according to the powerslot site the slots function the same in both directions but the rotor vents are angled and must be installed a certain way. i have them so the air blows out, vs sucking air in.

"L" is driver side. I can tell by the way the internal vanes are oriented in your picture - you have them mounted the right way. Good question though, never thought of that.

From StopTech:



(Driver's perspective looking forward)

Note: The direction of the slots or hole pattern should not be used to determine what side of the vehicle to place a rotor. Different manufacturers may have different strategies for slot and hole patterns. The only correct way to determine what side a directional rotor goes on is the internal vane direction.

Time for new rotors. I am very satisfied with the Royalty drilled/slotted I used last time, but they have been worn down by the HP+ pads (they no longer have slots, only holes!). There have been no warping issues over 20k+ miles. So it seems we can't really win at this game. Either crack/warp rotors over time from heat and uneven build-up, or use an abrasive pad that keeps rotors true, but wears them down after a few thousand miles. I prefer the latter method.

So I ordered a set of slotted front/rear rotors for my '98 from brakeperformance.com. These are slightly less expensive, and they also make a matching slotted rear rotor, which is nice. I went slotted without holes so that there is more material to resist the wear from the pads. Btw, my HP+ pads appear to have lots of life remaining. Some info on the new supplier:

• Machined in the USA (I am a bit concerned about the iron quality, as they don't say where it is cast).

• Free Shipping to Lower 48 states.

• Drilled/Slotted & Dimpled/Slotted also available.

• LIFETIME warranty against materials and workmanship defects. 2-YEAR warranty against warping (Details).



Front pair: $140.06
Rear pair: $109.64

Shipping: $0.00

Total: $249.70

Link for '98 models (early models visit home page):

Link

Baer Brake Systems on drills and slots:

What does "cross-drilled and slotted" mean?

The expression refers to two separate processes, both of which are carried out on both Baer´s EradiSpeed and DecelaRotor lines. The first procedure involves drilling rows of holes through the friction surfaces of the rotor, the second refers to milling a series of shallow grooves from the center of the disc towards the edge. In combination, the processes are aimed at making the disc better ventilating and more effective. In addition this gives the rotor a more aggressive and purposeful cosmetic appearance, particularly with today´s open-patterned alloy wheels.

What are the benefits to cross-drilling, slotting, and zinc-washing my rotors?

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.

What does slotting do?

Slotting increases the bite of the pads and helps the car to decelerate more rapidly. The process doesn’t involve removing as much metal as cross-drilling, so it doesn’t result in as great a weight saving. Slotting is however, still effective in combating the problem known as "outgassing". This occurs when, at very high braking temperatures, the bonding agents used in some brake pads produce a gas. Under extreme conditions, this gas can create a pneumatic cushion between pad and rotor, giving a driver a normal pedal feel but reducing the amount of friction being generated. The slots pump away this gas and restore full contact. The "micro-shaving" effect of the slots also serves to de-glaze the pads (this is why the edges of the slots on EradiSpeed rotors are not chamfered or "radiused"). It also tends to even out the wear across the brake pad faces, increasing the effective contact area. This can extend rotor life.

Does a disc need to be cross-drilled and slotted?

Not necessarily, however, in order to create a high-performance disc suitable for the widest range of applications, we have incorporated these features into the standard EradiSpeed product line

Will slotting or cross-drilling my stock rotors improve my car's stopping performance?

DEFINITELY NOT! Cross-drilled or slotted rotors do produce a strong visual appeal behind a modern open wheel, and they do have a performance edge when pad outgassing occurs. Outgassing occurs at extreme temperatures when the bonding agents that hold the pad material together break down into a gas form. This gas creates a pneumatic barrier between the rotor and the pad, reducing friction. Cross-drilling or slotting creates a path for the outgassing that occurs during extreme braking conditions. However, these conditions can virtually never be reached on the street! Short of a complete system, performance brake pads, a proper Teflon lined braided stainless steel hose set and quality brake fluids are the only direct replacement upgrades that can be combined to deliver measurable stopping improvements in the context of direct replacement components on the OE brake system.

What brought this topic up.???
Just a refresher course,?

Did you know that modern brake pads do not outgas?

I didn't, welcome to 68.

I thought all the research was already done.?

And just to poke a hole in all your bubbles, Nissan has proven in their own sports car, the Z, that no matter the slots and holes, you can still build a brake system that fades into oblivion after repeated use because the binder in the pads melts, and the fluid boils...
(Car and Driver)

Eldo wrote:

And just to poke a hole in all your bubbles, Nissan has proven in their own sports car, the Z, that no matter the slots and holes, you can still build a brake system that fades into oblivion after repeated use because the binder in the pads melts, and the fluid boils...
(Car and Driver)

Hmmm.... wonder if they tried switching to EBC Redstuff pads and dot 3/4 synthetic (Valvoline or Prestone) fluid?

Albertj

It really had nothing to do with slots and holes.

The C&D reviewers tried replacing both the pads and the fluid, with some success. In response, Nissan now provides a semi-metallic pad option to replace the organic OEMs. The new pads resist the heat better, but they do not solve the problem. The fluid was determined not to be part of the the problem. The rotors were also not the problem (C&D confirmed this with complete certainty).

The problem was Nissan forgot to provide a good path for air to cool the brakes, so C&D recommends owners install a venting system if they are intending to race the car. With only the better pads, the car is fine on the street. It's probably fine with the original pads, unless the car is pushed hard with multiple hard stops. The initial stopping distance was fine all along.

Baer's info on drilling and slotting is significant to me, because it partly debunks the idea that holes & slots will actually help stop you faster in a street setting, which I think many, many people believe. What holes do is make the rotor lighter, and slotting helps even the pad wear and extend rotor life. The slotting advantage seems legitimate. But loosing a couple of ounces of unsprung mass from drilling holes seems a bit far-fetched. Remember, loosing weight also impedes the system's cooling capability. And there is the increased risk of cracking with drilled holes.

In racing situations, holes and slots might actually help in certain situations. For example, most newer carbon/ceramic rotors (Enzo, ZR1, Carrera GT) are drilled. Maybe they are not as susceptible to cracking? However it's contradictory to try and copy this look with iron rotors - if the same weight-savings advantage no longer applies. In iron street rotors, holes seem to be mostly for looks. Slots seem to offer more real substance, and this is one of the reasons I've switched to slotted-only for iron rotors. Waiting for the day when carbon/ceramic rotors are available at an affordable price - then maybe we'll see holes make a come back.

AA wrote:

It really had nothing to do with slots and holes.

The C&D reviewers tried replacing both the pads and the fluid, with some success. In response, Nissan now provides a semi-metallic pad option to replace the organic OEMs. The new pads resist the heat better, but they do not solve the problem. The fluid was determined not to be part of the the problem. The rotors were also not the problem (C&D confirmed this with complete certainty).

The problem was Nissan forgot to provide a good path for air to cool the brakes...

Right, my point was that despite the hardware, the system could still be lacking - adequate ventilation being part of the system...

Speaking of which, while drilling the rotors does remove some mass, and "gives the rotor a more aggressive and purposeful cosmetic appearance" ( ), I'm pretty sure it mainly increases ventilation.

The NISMO package they tested had plain rotors. What the C&D test tells me is that pads are one of the most critical parts of stopping the car. 14" rotors and 4 piston calipers aren't going to matter if the pads aren't ready to take the heat. The other lesson is that exterior car styling is becoming more and more about looks and aerodynamics. Once in a while they drop the ball on some functional aspects of the design. The average car probably doesn't cool the brakes any better, but when you equip giant rotors, giant calipers & pads, with the intent to create a capable sports car, you must cover all the bases. In this case it was cooling that lacked. Now everyone can stop mocking Ferrari for using those big front cooling ducts - they have a very real purpose!

I agree the holes can help with ventilation, but only effectively with specially designed vented rotors like StopTech's Aero Rotors, which actually increase air flow through the disk as it rotates. But merely having holes and vents, we can't assume this will happen with any rotor, although it just might. I think most race drivers stay away from drilled holes, relying on large discs, proper pads, and adequate ventilation to manage the heat. Really, that's all you need to do.

AA wrote:

Now everyone can stop mocking Ferrari for using those big front cooling ducts - they have a very real purpose!

Most of the airflow is going to be used by the radiators. Relatively little goes to the brakes, judging by this McLaren F1 diagram.

The F430's intakes are larger than the F1's, but the F1 has a cooling problem. I'm going to guess the F430's extra intake size is for larger radiators.

The vents on the side of the front bumper dump air from the radiators, and the openings on the rear fenders are ram air intakes for the engine - Link

From your link: "The brakes benefit from a greater airflow thanks to larger intakes and bigger diameter ducting."

If the Ferrari front ducts provide for both radiator and brakes, they really do need to be as big as they are. The irony with the 370Z is how it has these giant, flat areas on the outsides of the front bumper, where brake cooling ducts (large or small) could easily fit. And I would think it would only help with aerodynamics to let air flow through. But in the effort to capture the something purely aesthetic, they overlooked the obvious.

I ordered a set of those slotted rear rotors for $109 since mine are due for a changing and are making a squeak i cant seem to fix.

Aaron, let me know when you get yours in the mail. it means mine should be soon to follow. i havent gotten any shipping emails from them yet, but for free shipping i guess i cant complain.

I received a delivery notification last week saying they were due arriving tomorrow the 27th. Watch for it in your email.

AA wrote:

From your link: "The brakes benefit from a greater airflow thanks to larger intakes and bigger diameter ducting."

Yes, I read that line, which only means the F430 Scuderia's brake ducts are bigger than the 360 Modena's brake ducts.

AA wrote:

If the Ferrari front ducts provide for both radiator and brakes, they really do need to be as big as they are.

But not for the brakes alone, which may only have a duct a few inches across.

Here's a C5 ZO6 duct - Link

As for radiator cooling, I'd like to know why there are two radiators on the corners instead of one in the middle. That would seem to be more reliable, more easily packaged, and it would give a better weight distribution.

Here's a Porsche 959 that appears to use a similiar cooling arrangement, with a central radiator -



But maybe it has one on each corner too?

It'd be nice to have diagrams of what all these cars look like beneath the sheetmetal.

Received the Brake Performance rotors today. They sent me black instead of silver, but it's not a big deal. I'm not impressed with their coating job, but it won't matter much once I install and bed the pads in.

Notes after install:

Braking is great, just like before, but after about 20 hard stops to eat through the black paint. Rears took about 5 extra applications of the P-brake at 70 mph to remove their coatings.

I repeated Royalty Rotors' technique of measuring run-out with a caliper & bench vice, even though the Brake Performance instructions didn't require it. I found that rotating the rotor a couple positions meant the difference between .006" and .002" measured run-out. Takes longer, but worth doing this step, imo.

Pad wear was very consistent. Fronts appear about 50% worn, and near perfectly even and flat - all four were almost identical. I will probably replace these in about 20k miles.

Rear pads showed less wear, but they exhibited a condition where each pad was worn down more near the leading edge than the trailing edge, relative to wheel rotation. It seems the single rear piston is just too small to keep the rear pads from teetering some under braking. I noticed this on the last set of pads as well. The solution was to swap the rear sets from left to right axles, so the previous leading edges are now the trailing edges, and vice-versa. Hopefully this will allow the condition to reverse, evening the pads out.



One last note on the Brake Performance slotted-only rotors I purchased. Their design is such that each of the five slots are located directly behind each of my five wheel spokes, so from the side it looks like my rotors are solid. This is different with every wheel/bolt pattern, so it's not the fault of the rotors. I actually like the stealth effect, but for those who want the look of slots, make sure you pick a pattern that works with your wheels - something to consider before you buy.

Here's a site that has a bunch of car cut aways -

Link

The pre-McLaren F1 supercars have center mounted radiators, the post Mclaren F1 cars have a small radiator on each corner.

Does anyone know of an earlier car than the McLaren F1 that used this radiator arrangement?

Regarding brake cooling, I found an interesting article on the subject:

http://www.stockcarracing.com/techarticles/scrp_0704_brake_temperature_control/index.html

They say to always try making the cooling ducts as large as possible to maximize air flow. The larger ducts help funnel more air through the ducts:

"Wind tunnel testing has proven that the area of highest air pressure on a race car is the center of the valence below the bumper. This, of course, is the location for the radiator inlet, so your best location for brake cooling inlet holes is on either side of the radiator box.

For an air inlet, cut a hole in the front valence that's the maximum size allowed by your rule book. For just about any Saturday night racetrack, you need all the airflow to the brakes you can get. For example, many racers cut a round hole in the valence the same diameter of the cooling duct, even though the rules allow a larger opening (often 4 by 3 inches or 12 square inches). You can increase airflow to the brakes by making the opening as large as possible and using a section of solid duct to funnel the incoming air into the flexible duct."

One thing I did not know - the cooling duct must always lead to the center of the rotor, because that's where the supply air is sourced from as it cools the rotor, exiting on the outside edges of the disc. If you try to aim the duct at the caliper, or the side of the disc, it won't work.

Has anyone on here tried using the AC Delco durastop performance rotors? They carry them for all year rivs and judging from the pic on rockauto they appear to be drilled and slotted. Ironically they sell the 95/96 for $6.10 MORE than the 97-up, even tho the 97's are larger. I have to do my front brakes soon and I thought I might go with these unless someone has a good reason why I shouldn't. Rockauto also lists a durastop pad in both semi-met and ceramic. Not sure I'd use the pads, just throwing it out there to see if anyone has an opinion.

Opinons on Durastops at Corvette forums:

http://www.c5forum.com/cgi-bin/ultimatebb.cgi/topic/2/1797.html

http://forums.corvetteforum.com/c5-z06-discussion/1431106-rotors-ac-delco-durastop-performance.html

Cadillac forums:

http://www.cadillacforums.com/forums/suspension-brakes-tires/35140-ac-delco-durastop-rotors-99-sts.html

I think the Durastop rotors are okay, if you don't mind the price. The pads are probably fine if you are just looking for low dust and noise. For higher performance, or for someone who's hard on the brakes, I'd change to a carbon metallic pad. Pads seem to be a bigger factor in braking performance, rather than the style of rotor you choose.

Thanks for the info AA. Like I said I have my front brakes coming up soon and I'm seriously considering these rotors. I know they're a bit pricey but OEM parts are usually known for dependability. With that being said I doubt I'll go for the durastop pads as they're likely not going to be as aggressive as I'd like. I don't need anything race ready but I would like more initial bite than what the stockers give me now. My one concern is brake squeal. I HATE it! I enjoy washing the car so dust isn't a problem for me, but I will not tolerate for my brakes to squeak even once when cold. I don't mind deceleration noise but squeak drives me insane. Did you have any noise with the hawk pads you were using?