FAQ: Brake Rotors and Pads

Seems like an easy decision: Hawk HPS pad compound. Reasonably priced, not too bad on dust, and very quiet. They also stop very well, especially when hot, and will not abrade the rotor surface.

The pads I use now are HP Plus. They stop a lot faster, but tend to squeal at times, are very dirty, and will wear down rotors after 20-25k miles. I continue to use the HP+ pads, because I am still amazed at how quickly they decelerate the car.

AA wrote:

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.

There's got to be more to it than this. For starters, the center of the rotor is not infinitely large. If you've got a four inch diameter sweet spot, you can't use a bigger duct unless without compressing the air, which means drag. Maybe o.k. for a car that doesn't need to go over 200 mph.

Derek wrote:

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.

I used them with Durastop pads on my Riv, they were OK. Currently using ATE rotors and Raybestos ceramic pads.

Albertj

Derek wrote:

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?

I have Hawk HPS pads (on my 2nd set) and powerslot rotors w/fbody calipers right now.
As for dust...these pads are some of the worst i've seen! I am cleaning my rims every single day if i want them too look good. Note: I have chrome rims with a 4"+ dish that seems to collect all the dust that shoots off the brakes.
I will say that this combo is the best i've found so far. no warping, stops HARD, and doesnt make any noise (i did use stop-squeak on the pads).

As far as initial bite, the HPS pads, and most other track pads, dont have an ultra responsive "bite" like some new cars are having (toyota/lexus for example). They are designed to work well in a certain operating temp which is not cold.

I will say one of the cool things about the combo i have is that when i get on them really hard (from 70+ when they are warmed up) i get sparks shooting off the rotors! i am trying to get a picture of them, but it's proving really hard to take a picture from another car that just cant stop as fast
I even have dash marks on the rim where the sparks leave little dust trails.

Quote :

There's got to be more to it than this. For starters, the center of the rotor is not infinitely large. If you've got a four inch diameter sweet spot, you can't use a bigger duct unless without compressing the air, which means drag. Maybe o.k. for a car that doesn't need to go over 200 mph.

Jack, I chose some poor wording in my previous post. I think what they are saying is the opening for the duct must be as large as possible, not the duct itself. They advise using a 3" duct, but connecting it to an opening port as large as 12" will increase air pressure in the tube, increasing flow. It's a funnel effect, or ram-air as some call it.

Matthew, maybe I felt the HPS didn't dust too badly because the HP Plus are that much worse. Even so, I had no trouble removing the dust from my chrome rims, and my new painted rims are even easier to clean.

AA wrote:

Jack, I chose some poor wording in my previous post. I think what they are saying is the opening for the duct must be as large as possible, not the duct itself. They advise using a 3" duct, but connecting it to an opening port as large as 12" will increase air pressure in the tube, increasing flow. It's a funnel effect, or ram-air as some call it.

Is this for a low speed racing event? I've been reading about the McLaren F1, which uses fans to pressurize the air going to the brakes. By doing this they avoid huge intakes that mess up the aerodynamics?

I may have been wrong to say the 360 Modena copied the styling of the McLaren's front intakes. Before we started this discussion I thought the McLaren's front intakes were for style, which in retrospect was a foolish thing to think.

I went and looked at the underbodies of a bunch of model cars I've got, and it's interesting to see how they evolve.

Countach - basically flat, but covered with exterior bracing, and the engine bay is wide open.

Diablo - very flat, only the oil pan is exposed, but no controlled exit of the air flow

XJ220 - extremely flat, the engine is fully enclosed in an aerodynamic tub and only the lower a-arms are exposed. Air exits through a rear diffusor.

Unfortunately I don't have a model of the McLaren F1, and can't find pictures of the underside.

I'd like to see if it doesn't have something special in the front equivalent to a rear diffusor, that caused the shift from a big center radiator to the two small radiators on the sides. If the highest pressure area on a car is at the center air dam, that would be a good place to reduce drag. The McLaren F1 and 360 Modena both have a raised center section - what is it for?

I'm thinking Ferrari and Lamborghini copied the functionality of the McLaren F1's front end. Others may have too.

I would guess there is little need for brake cooling at low speeds, unless the car is heavy. Friction operates on a non-linear curve - temperature increases 4X when you stop from 2X speed. Weight is the other variable. like you said, the fans can replace the the need for larger openings, but at very high speeds, a larger opening can flow better than a fan, so the fan can become a restriction. For this reason, the ultimate set-up is a Y-split before the brakes, one half leading to a fan, the other straight to an opening. This can make the duct openings even larger, or more numerous.

You could be right about the competitors copying the McLaren, which itself took a lot from F1, or we can just say F1 heavily influences some supercars, as it surely did for the F40, McLaren, F50, Enzo...

AA wrote:

I would guess there is little need for brake cooling at low speeds, unless the car is heavy.

In terms of racing, I was thinking the opposite - the low speed racing events I see have lots of turns and braking, whereas in an event like NASCAR you get high speeds but little to no braking.

AA wrote:

You could be right about the competitors copying the McLaren, which itself took a lot from F1, or we can just say F1 heavily influences some supercars, as it surely did for the F40, McLaren, F50, Enzo...

I don't see an influence on the front air dam coming from F1, since those cars don't have front air dams

I can't think of a type of racing car that could have influenced the look of the McLaren's front end, but I haven't seen them all.

Quote :

In terms of racing, I was thinking the opposite - the low speed racing events I see have lots of turns and braking, whereas in an event like NASCAR you get high speeds but little to no braking.

It's the frequency of the corners that causes the heat to add up in that case. But if the same cars were given an extra 100 HP and could accelerate faster on the same track, their brakes would run hotter, so the need for cooling would be increased.

With NASCAR oval track racing, the high speed is constant, not as much braking, thus less need for cooling. But if the same cars were robbed of 100 HP, top speed lowered as a result, their need for brake cooling would be even less.

There are high speed tracks with turns. If you ever watch a LeMans/GT race at night, their rotors are actually red hot as they brake at the end of the main straights. Fortunately, the high speeds force more air through the ducts, cooling the brakes, so it works. With tracks, it's not so much high vs. low speed as it is more vs. less frequent stopping.

Not sure about the looks being influenced by F1 - I was referring more to the functional aspects of the cars.

How can super car manufacturers be copying front air dam functionality from F1 cars that don't have front air dams?

I wasn't speaking specifically about air dams, just F1 functionalities in general (intake, cooling, engine/drive configuration, driver position, brakes).

Some information on brake pad compounds from Pegasus Racing and VWVortex.com, Racing Brake, and other sources. Puts into perspective the differences between pads made for racing vs. street vs. OEM:

OEM:

Examples: Mintex Redbox, Hawk Ceramic
Friction coefficient = 0.30-0.40
Temp before fade: 600-700°F
Duty: street use only
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Hawk:

HPS (F): High Performance Street. This compound will outperform OEM pads without sacrificing street manners. Stops 10% shorter than OE pads. A good choice for Solo II; also recommended for amateur to intermediate drag racing. Effective from dead cold. This versatile compound has proven to be the ultimate dual purpose street and strip material available on the market today. Recommended for amateur to intermediate forms of drag racing. Can also be used in most light duty Dirt applications where low temperature cold effectiveness is required. An excellent street pad.
Operational temperature range is 100-800 degrees F.
Friction coefficient = 0.41-0.55 (EBC pads have higher cF, Greenstuff has poorer performance on heavier cars)
Temp before fade: 700-900°F
Duty: light auto-cross and performance street use

Comparable pads: EBC Greenstuff (cF = .46 -.55 / fade: 1000ºF), EBC Redstuff (cF = .30 -.50 / fade: 1380ºF), Porterfield R4-S, Axxis Ultimate (cF = 0.46 / fade: 1000ºF)


HP Plus (N): This unique compound can take the heat at the track and get you home safely. Designed for the serious street and Autocross racer. Due to the dramatic friction level produced by this product, rotor wear, noise, dust and pad life may be affected when used for city driving. Designed as an autocross (Solo II) and track day (Solo I) compound. Very wide temperature range makes it suitable for all forms of autocross, yet still streetable. Expect an increase in dust, noise, and rotor wear.
Temperature Range: 100-800° F, for short periods of time, up to 900 degrees F.
Friction coefficient = 0.46-0.55
Temp before fade: 900-1300°F
Duty: light track days, auto-cross, and performance street use

Comparable pads: EBC Yellowstuff (cF = .50), Ferodo DS-2500, Ferodo DS-2000, Carbotech Bobcat, Carbotech Panther Plus, Mintex 1155, Carbotech AX6 & XP10, Pagid RS4-2-1 & RS4-2


DR-97 (J): Excellent static and dynamic coefficient of friction. Smooth linear torque. Low pad and rotor wear. Brake pads specifically designed for use in drag racing applications.
Temperature Range: 100 - 900º F.
Applications: Drag Racing


Black (M): Medium torque compound with high initial bite, for grass roots racing. This material was designed to be a good, all purpose low cost racing pad. Recommended for Dirt Circle Track, Dune Buggy and light duty Road Racing applications. Requires gentle initial application of the brake pedal to avoid locking. Recommended for very light sedans, small formula cars, and sports racers.
Temperature Range: 100-900° F.
Friction coefficient = 0.50-0.68 (depends on specific race application)
Temp before fade: 1300°F+ (depends on specific race application)
Duty: track use only

Comparable pads: Ferodo DS-3000, Porterfield R4, EBC Yellowstuff (cF = .50)


Blue 9012 (E): Medium/High torque brake compound with medium initial bite. A reliable performer with a wide temperature range. Low pad and rotor wear rate with good brake modulation characteristics. #1 pad material for SCCA. Recommended for Production, IT, F2000, Formula Ford, S2000, CSR, and DSR. Recommended for Road Racing and Rally applications where low to mid temperature effectiveness is critical. Also known as "Blue 9012". Temperature Range: 250-1000° F.
Friction coefficient = 0.50-0.75 (depends on specific race application)
Temp before fade: 1300°F+ (depends on specific race application)
Duty: track use only

Comparable pads: Ferodo DS-3000, EBC Yellowstuff (cF = .50), EBC Bluestuff (cF = .55 -.75), Pagid RS19/RS29, Porterfield R4


MT-4 (L): Medium/High torque and temperature compound with Medium/High initial bite. Brake pads designed for circle track cars under 2800 lbs without high deceleration rates.
Temperature Range: 400-1200º F
Duty: Pavement Circle Track under 2800 lbs.


HT10 (S): Very high torque with a smooth initial bite. Good rotor and pad life. Excellent modulation with good release characteristics. Recommended in NASCAR, Trans-Am, and all forms of road racing. Works well as a rear pad with HT14 in front. Recommended for sedans, sports racers, and formula cars with downforce, including GT, Formula Atlantic, F2000, F3000, S2000, CSR, and DSR.
Temperature Range: 300-1300° F.

Comparable pads: EBC Bluestuff (cF = .55 -.75), Pagid RS19/RS29


HT14 (V): Extremely high torque with aggressive initial bite - designed for cars with very high deceleration rates and downforce, and lots of grip. Excellent release and modulation characteristics. Recommended in Trans-Am, GT1, CART, Formula Atlantic, F2000, F3000, and Prototypes.
Temperature Range: 300-1400° F.

Newer "Dynamic Torque Control" series from Hawk. I've heard this line will eventually replace HP+ and a portion of their current line:

DTC-05 (H): Developed specifically to meet the demands of lower torque Dirt Track Racing. This friction formulation provides very controllable, higher temperature performance as compared to stock pads.
Temperature Range: 100-900F.

DTC-15 (): Developed specifically to meet the demands of Dirt Circle Track applications. DTC-15 brake pads are a medium torque compound (less torque than DTC-30, more than DTC-5) with superior release characteristics and excellent cold effectiveness.

DTC-30 (W): Brake pads designed Specifically for Dirt Circle Track applications. Uniquely controllable torque with smooth consistent feel and bite. Superior Release and torque control characteristics.
Temperature Range: 100F-1200F.

DTC-60 (W):High torque with less initial bite than DTC 70. Superior release and torque control characteristics. Brake pads designed for cars with high deceleration rates with or without down force. Recommended for use with DTC-70 when split friction between front and rear axle is desired.
Temperature Range: 400-1600° F.

DTC-70 (U): Extremely high torque with very high initial bite. Designed to be the most controllable racing brake pad available. Intended for heavier sedans and formula cars with downforce. Available for a limited selection of racing calipers. Recommended for Trans-Am, GT1, CART, Formula Atlantic, F3000, and Prototypes.
Temperature Range: 400-1600° F.

Here's a graph I made up to show some hypothetical performance curves you might expect from various Hawk pad compounds, and typical OEM (these are only guesses based on the above specs and descriptions. I haven't used or measured every one of these pads):



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Performance Friction:

Z Compound: is the high-performance street compound. The Z Compound is race worthy in many applications while still suitable for everyday street use. The "CMS", "S", and "69" compounds are older, more mild street compounds.

80 Compound: was the first Carbon Metallic race material from Performance Friction. A favorite for many applications where pedal modulation is difficult, and brake balance or chassis set-up requires a more forgiving pad. Lower torque than the 83 Compound.

83 Compound: is a super high torque compound that requires finesse. The torque curve rises with heat to handle the most extreme applications. Gradually being replaced by the 01 and 03 Compounds in most applications.

90 Compound: was developed at the same time as 93 and is very similar with lower torque output. Used by several race driving schools including Bob Bondurant, Derek Daly, and Jim Russell because of its forgiving nature and long life. Gradually being replaced by the 97 Compound in most applications.

93 Compound: was developed after the 83 compound, with higher initial bite and better release characteristics for improved trail braking into corners and easier modulation at threshold braking. It is also kinder to the discs, polishing discs smooth even under severe conditions. Pad life is also very long. Requires finesse to prevent over-slowing the car. Gradually being replaced by the 01 and 03 Compounds in most applications.

97 Compound: has a very flat torque curve with less overall torque than the 01 Compound. The 97 Compound was formulated with excellent modulation and release as the primary objectives. Extremely easy on discs and very long wearing. Lowest friction of any PFC compound. Recommended for applications where wear and modulation are more important than ultimate torque.

01 Compound: has a very high, very flat torque curve for good initial bite, excellent pedal modulation, and a fast, smooth release. Torque rises very little with temperature, which makes these pads very predictable. Easy on rotors and long-wearing. All-purpose pad for a variety of racing applications.

03 Compound: has higher initial bite and higher overall torque than the 01 Compound. Torque rises slightly with temperature to handle severe braking conditions. Excellent modulation and release characteristics. Recommended for high grip, high downforce applications.

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Pagid Race Pads:

RS-7 BLACK: (Carbon-based) A material developed for use on rear axle of front wheel drive circuit racing cars with low rear axle weight. Lower friction levels help to reduce rear wheel lock.

Cold: 212ºF-572ºF / Working: 572-932ºF / Max: 1,022ºF / cF = 0.32 0.33 0.35 0.37


RS4-2-1 BLACK: (Carbon-based) A very stable material with low disc wear. It has a wide operating range with good low temperature performance and low brake noise. Fitted as original equipment on many high performance road vehicles, this is the best all round pad for road use.

Cold: 212ºF-572ºF / Working: 572-932ºF / Max: 1,022ºF / cF = 0.36 0.38 0.42 0.45


RS4-2 BLUE: (Carbon-based) The most popular material (known as 'Pagid Blue'), RS4-2 gives a good low temperature response. It is very stable with superior modulation and feel. RS4-2 has a medium co-efficient of friction with good pad and disc life. Suitable for many applications especially gravel rally and wet tarmac, where control is needed.

Cold: 212ºF-572ºF / Working: 662-1,112ºF / Max: 1,202ºF / cF = 0.4 0.42 0.46 0.49


RS4-4 ORANGE: (Carbon-based) This material has a high friction level especially at high temperature. It is better for high temperature applications than RS4-2 and has a very stable torque pattern. Suitable for rear axle use on Touring Car applications and very popular in Porsche racing.

Cold: 212ºF-572ºF / Working: 662-1,202ºF / Max: 1,292ºF / cF = 0.39 0.4 0.48 0.53


RS-19 YELLOW: (Ceramic-based) This material provides very good performance at all temperatures with immediate brake response. Very stable pad on ceramic base, with excellent fade resistance and low disc wear. Suitable for endurance racing or applications where exceptional life is required.

Cold: 212ºF-572ºF / Working: 752-1,292ºF / Max: 1,382ºF / cF = 0.4 0.43 0.47 0.49


RS-14 BLACK: (Ceramic-based) A high friction, high temperature material with enviable pad life at this level of friction. Very kind to discs, easily modulated and resistant to wheel lock in extreme use. Suitable for Touring Car, WRC, GT and other forms of medium weight single seater race cars that have good levels of grip.

Cold: 212ºF-572ºF / Working: 752-1,292ºF / Max: 1,472ºF / cF = 0.44 0.47 0.49 0.54


RS-15 GREY: (Ceramic-based) The newest material, a development of RS-14 which combines a 20 percent higher friction level with an improved initial bite. RS-15 has a very good life and exceptional release characteristics. It is also very easily bedded in comparison to it's competitors. Suitable for Touring Car, GT and other applications requiring very high levels of friction and high temperature stability.

Cold: 212ºF-572ºF / Working: 752-1,472ºF / Max: 1,652ºF / cF = 0.50 0.54 0.57 0.62

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EBC:

Redstuff: Low dust EBC Redstuff is a superb pad for fast street use and targets High HP imports, muscle cars and prestige European cars. EBC Redstuff Ceramic pads REDUCE DUST emitted by OEM pads by approx 80%. Redstuff pads also reduce rotor wear so that rotors and pads last longer whilst delivering great brake performance. For optimum lifetime in track use, EBC still recommend drivers to upgrade to their Yellowstuff or even the new Bluestuff range but if Fast street is what you need, EBC Redstuff Ceramic is the pad to choose.


Yellowstuff: compound is essentially a race pad but with a BIG difference in that it works from cold and can be safely used on the highway. If you want the ultimate in high friction braking, this is the pad to choose. Brakes feel superb from first touch of the pedal and stay effective up to race temperatures. EBC Yellowstuff is designed for faster imports and muscle cars where maximum stopping is the prime requirement and for short duration track use. Its dust rating is similar to OEM parts. All pads come with edge chamfers, center line slots, noise reduction shims and OEM hardware as needed. All EBC pads feature the EBC Brake-In surface coating which helps pads seat quickly after install.


Bluestuff: NDX Formula brake pads are the ultimate high friction race pad, even superb as a brake upgrade for street driving. Due to the high initial or cold bite, the Bluestuff pads feel great from first pedal right up to race temperatures. The friction level of these pads is over 0.6µ which is huge in friction rating terms. Built with interlayer technology and multiple spigot holes for superb pad retention, Bluestuff will impress all sportscar and muscle car drivers in track use and even on the drive to and from the track. EBC Bluestuff uses a revolutionary man made fiber and does NOT employ cheap steel fibers that cause hot sparks and damage caliper seals and wheel rims alike. Bluestuff is also easier on rotors than most race pads. Designed for mid to heavy car weights and horsepowers, for lighter vehicles EBC Yellowstuff is your race and fast street choice option.

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Racing Brake:

ET Series Characteristics:
* Excellent Modulation
* Consistent friction and torque output
* Run from ambient temperature (even in cold winter morning) - ET500 & ET700
* Extended life if they are used under the temperature guide
* Affordable pricing

ET300:
* Upgrading stock pads to street performance
* Very low dust, no squeaking

ET500:
* Great for the street, good for occasional light track events
* Guaranteed no-fade up to 1000°F / 537°C
* Very low dust, none to minimal squeaking

ET700:
* HPDE and entry level racing, also good on the street
* Excellent heat characteristics
* Guaranteed no-fade up to 1200°F / 648°C
* Occasional low squeaking on street driving - RB brake shims may be added as needed

ET800:
* Excellent heat characteristics and modulation
* High temperature, guaranteed no-fade up to 1400°F / 760°C
* Lower torque and deceleration rate than ET900 series

ET900:
* For motorsports racing only (not recommended for street driving)
* Excellent heat characteristics and modulation
* High temperature, guarantee no-fade up to 1600°F / 871°C
* High torque and high deceleration rate



Links: http://www.pegasusautoracing.com/document.asp?DocID=TECH00062

http://forums.vwvortex.com

http://www.perfectbrakes.com/products.asp?cat=1624

http://www.racingbrake.com/v/main/rb_pads.asp

WOW! good stuff.

It makes me want to try them all.

I'm slightly interested in the EBC Bluestuff race compound. EBC says you can use it on the street no problem; it would appear to be the perfect all around pad, but it costs $150 for the front set!

If you need that kind of braking power, $150 isn't very much.

True. It's tempting, but now I'm concerned about having too much friction. Besides, the HP+ pads are holding up very well so far.

Since I'm rollin in a 95', guess I will just have to stick to good ole Raybestos pads and rotors.

There are several different rotor & pad combinations that will fit your '95; many of the pad types are mentioned above. At least three slotted front rotors that are a direct fit, as well as pad compounds from OEM level on up to the HP10 race compound used for NASCAR. If you upgraded to Hawk HPS pads alone, I think you would be surprised at the difference.

AA wrote:

True. It's tempting, but now I'm concerned about having too much friction. Besides, the HP+ pads are holding up very well so far.

I've wondered about that too. whats the max my car can handle before stuff starts breaking off from the -g force? I mean at some point it will be enough stress to start snapping suspension parts, and could it possible set off air bags?

I'm not so worried about the structural stress. I think the tires are going to slip before anything breaks. There's really no way the airbags could go off from braking - it's still too gradual of a deceleration.

What I don't want is brakes with so much initial bite that that they instantly go into ABS mode. With such high friction, we may not be able to modulate the brakes as well, so the car may be harder to control, say, in a hard turn.

Gotcha.
Right now i have a problem with my rear trans mount clanking under hard breaking and acceleration.
Just ordered a new one from AZ for $50 and i'm hoping it's not too big a PITA to install. I will also be filling the voids with poly.

Me too on the rear mount - I'm right behind you after I replace control arms and KYB struts. I'm pretty sure I hear a bad strut bearing.

Here's a pic of new Brake Performance slotted rotors after 2500 miles. They are still straight, wear is even (no grooves), stopping very well so far with Hawk HP+ pads. Coated areas are resisting rust pretty well. Happy with these for the $140 price.

Do you think the stopping power is compareable to EBC pads and rotors?

I like the set i have too. So far its the first set i havent had warping or cracking issues with.
Although my front ones have rust on the edges and inside the vents b/c when i was breaking them in i overheated them and cooked the paint off.
That was the first time i've had the HPS pads severely faded too.