Avalon Racing

This is part of the series we did on brakes and technology for our site. Use this basic guide to help you choose the right brakes. There is calculations in the article, which are the simplified versions - so all Physics majors, lets not get into a major discussion on the formula. The Formula used was done by the Brake Development mananger @ A/P

At the bottom is actual data from a Dodge Durango we did for comparison. This is done to show the impact with a 4600 + LBS vehicle.

Brakes:

Let's start the basic knowledge on brakes with the discussion of "directional" or not. Sport Rotors (drilled or slotted) come marked for a specific side. This is to optimize their functional cooling and out gassing. Sport Rotors can be used in either direction as they use a piller mounted vein for cooling. The Skyline, Brembo and A/P Brake kits use a radial vein and MUST be mounted directionally.

Now with this out of the way, I would like to provide some basic brake data written by a Racing Brake Development Engineer and myself. The goal is basic brake technology for racing, the street and why certain big brake kits are required. It will also aid you in the decision to use cross drilled, slotted or a combination rotor. Most use cost to determine the type instead of driving conditions. The wrong type rotor with the wrong pad combination in the wrong situations means trouble.

" Most true car enthusiasts are also committed gear heads. Not only can they wring the last amount of absolute power out of their ride, but still feel the need to take it to the next level.

Human nature being what it is, gives us the creative impulses to focus on power increases. The need for speed, while commendable, often comes at the expense of balanced power and delivery output and consumption. To create a truly great car, one must deliver all facets into account and make them work together. Simply put, the faster you accelerate, the quicker you need to stop. Cars that accelerate like an F-40 but brake like a Pinto on greased drums are very common. This is not only one of the slowest ways around the race track, but the most dangerous. Powerful fade - free brakes are a true characteristic of a noteworthy performance car. Oddly enough, many drivers do not take the time to fully understand the mechanics of the modern braking system.

The Principles: (applied in road racing and circle track)

Brakes function by turning kinetic energy into heat energy that can be released into the air, allowing the car to slow down or stop. If you remember Physics 101 in school, energy is neither created or destroyed within the system, it only changes form. Any object in motion has kinetic energy, and will tend to stay in motion unless acted upon by an outside force. You can calculate the amount of kinetic energy by this simple formula: Kinetic Energy = WxS2/29.9 where "W" is the weight in pounds of the car and "S" is the speed in MPH). Assuming your car weighs 2500 lbs. and travelling at 70 MPH, than you are strapped to 409700 ft-lbs. of kinetic energy. Ahead is a sign posted at 20 MPH ( for the turn). It is critical that we convert some of the energy so that we can take this turn in a controlled four wheel drift. To take the turn we will have to convert 376255 ft-lbs. of energy into heat. The formula for this is - [ 409700 - (2500x20 2nd / 29.9)] This will require a lot of friction and where a modern braking system comes into play. The rest of the article will give you an idea of the demands put upon the vehicles stock braking systems. While it can be done, you will see that with a modified systems the demands will be less strenuous on the brake system and the vehicle will have a higher recovery rate of heat to dissipation of kinetic energy.

I really need to note here that most if not all upgrade charts talk about power (in horsepower). BUT, it is my contention that regardless of who's chart (Stages) you use, the need for improved brakes and suspension starts at Stage III.

I'll leave out the rest of the variables as they will only confuse the basis of this article. Essentially, what we are all trying to achieve is to stop the car repeatedly and safely. By using cross drilled rotors for their intended purpose (performance street driving and limited track use) you can increase your performance greatly - provided the right heat range pad and fluid combination is used. Cross drilled rotors provide better initial bite characteristics. They will be more aggressive under lower temperatures and be able to vent out gasses to a much higher degree than a stock rotor and pad combination.

Generally true race cars use either a combination of drilled and slotted or just slotted. This is due to the fact that their fade characteristics will lessen at higher temperatures. Let's look at a 100% road race car for example.

These cars will use a slotted (and drilled at times) rotor exclusively due to the high demand that they put on the brake systems. These rotors will provide better braking at higher levels usually seen at an open track (circular) event or even endurance race. While these rotors work well under these conditions, they may not be suitable for lower temperature and low demand road race tracks.. They can hinder the braking capabilities due to the fact that they will need higher temps to work efficiently. Open road course events should be taken under more consideration. At race tracks that have long straights and deep turns, slotted rotors would be the preferred rotor due to its ability to out vent at higher temperatures. Rotor and pad combinations should/must be taken into account as well. Usually at an open track event, much more aggressive pad combinations are used. When using these combinations you will generally have to deal with a trade off in wear in either the pads or the life of the rotors. More aggressive pads will create more heat and friction thus causing accelerated rotor wear. Less aggressive pads will cause brake fade and accelerated pad wear. Do not forget that by using a pad that is too aggressive will cause the rotor to wear and require heat to work well. In some cases a pad can damage a rotor causing failure and damage. The balance could mean the difference in victory or failure

So what does this all mean, besides you should choose the type rotor, pad and brake system for your needs?

You just read the math and examples as well as some simple rations and characteristics - Now lets put them to use. Think about your particular application. While we all wish that we could out brake the world best drivers into turn one at LeMans, lets look at reality.

STOP - Sit Down - Have a drink (non alcoholic of course) and ask yourself the question:

While it is possible to put a monster brake system on your car you may never have the need or ability to use them properly. A big brake kit may look awesome but could leave you disappointed. You may never be able to get them to proper temperatures. For daily drivers and weekend enthusiasts, you may only need to go the way of the cross drilled / slotted rotors and a carbon based pad. I write this under the assumption you already upgrades your brake lines and fluid.

As I have also said numerous times - proper installation and break-in / seating of new rotors and pads is critical. Improper installations and mis-use is the number one cause of warped or in some cases cracked rotors. Never start the break-in of rotors is the run-out is more than 5 thousandths."


<img src="http://avalonracing.net/images/BrakeTest.jpg">

Hope this helps.

Copyright - Avalon Ent - Racing Division - All Rights Reserved

Maxima95GLE

While truly appreciate Avalon Racing's informative section on brakes (learned a few new things on cross-drilled brakes), I'd like to remind those out there that not all OEM brakes fade as bad as a 4,600 lb Dodge Durango after multiple stops.

I love information on cars, science, technology and the like, but I think everything needs to be presented in fair manner. I'll be graduating from medical school pretty soon, and it has been my hope to serve my future patients w/ the fullest information on potential decisions that they may make. Likewise, I would have hoped that Avalon Racing would have shown some conservation w/ their braking graph by showing braking information on a midsize car with 4 wheel disc brakes (the very heavy 4x4 Doge Durango has front discs and rear drums, I believe), as it deals directly with us. Show data on the Maxima, and then I think that would be a great comparison among the brake treatments.

I've been regularly reading car magazines for over a decade, and I must admit some cars will stop fade-free (or at least very close to being fade-free) on OEM brakes, and they're not necessarily the Ferraris, Porsches, MB, BMWs, Lexus, or the like. Some of the mundane, run of the mill brands ($15-$30K cars) w/o cross-drilled/slotted rotors/special pads will stop fadefree and even stop on a dime, approaching or rivaling the performance of the pricey exotic sports cars. I don't have the time to report on every car out there, but we don't need steel-braided brake lines or carbon fiber pads in some of our daily commuters or grocery getters, however, wanting those previous items, is a different matter.

For the racers out there, I think there is definitely a reason to upgrade the brakes. I'm just afraid that some of us non-racers will rush to spend needless money on upgrading brakes from reading the article. I'm not discounting the effect of upgrading our brakes, I'd just like to remind us that sometimes we don't need to upgrade our cars on what works perfectly fine.

Again, while I am very appeciative of Avalon Racing for their informative sections on brakes and car care, I think we'd all like to see a more fair approach to the information that has been or will be presented in the future on this forum. Lastly, the AR disclaimer paragraphs at the end about being "possible to put a monster brake system on your car you may never have the need or ability to use them properly" hits the spot, and so remember where your money goes. Thanks for your time.

MaxRod33

iTrader: (2)

Maxima95, you really know your sh*t!...LOL. You should ask Jambo to take the newbie status away from your name and put Car genious there...

Keven97SE

I always think it's funny how companies try to convince people that they need cross-drilled rotors, big front brake kit, steel braided lines, etc etc for their daily drivers when the fact is that usually a simple brake PAD upgrade will make enough difference to most folks to more than satisfy them.

Avalon Racing

First of all data is presented as information. Use it as you will. We also do not over sell a customer who does not do track time, performance driving etc.

Quite frankly the best upgrade for the daily driver is stainless steel lines and pads.

We are not trying to "convince" anyone to go to specific upgrades. You are clearly off the mark and missing the poijnt of education. Not every piece of data pplies to every situation.

Part of what we do help determine the right upgrade path for what the customer intends to do with the car.

As for the Durango chart. That was posted as a reference point. Clearly the Maxima or any other sedan in the same class would hav edifferent numbers. If we test a brake upgrade on Maxima's, then we will post results.

Regards

MI2KSE

I had read before that slotted and cross-drilled rotors were just marketing hype, so I pulled the follwing off the Internet:

Let’s look at some common rotor ‘modification’ and ‘performance’ upgrades that you may have been exposed to and try to separate the marketing from the engineering…

Super Sizing

Bigger rotors will make your friends think you are cool, bigger rotors look sexy, but bigger rotors do not stop the car. What a bigger rotor will do is lower the overall operating temperature of the brakes – which is a GREAT idea IF your temperatures are causing problems with other parts of the braking system. Take for example a F500 racecar – a small 800 pound single seat formula car. While the brakes are certainly much smaller than those found on a 3,000 pound GT1 Camaro, that does not necessarily mean that they need to be made larger. In fact, swapping on a GT1 brake package would probably do more harm than good – that’s a lot of steel hanging on the wheel that needs to accelerate each time the ‘go’ pedal is pushed. So, the motto of this story is bigger is better until your temperatures are under control. After that point, you are doing more harm than good…unless you really like the look (and hey – some of us do!).

Crossdrilling

Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the 40’s and 50’s, not a whole lot. Rotors were first ‘drilled’ because early brake pad materials gave off gasses when heated to racing temperatures – a process known as ‘gassing out’. These gasses then formed a thin layer between the brake pad face and the rotor, acting as a lubricant and effectively lowering the coefficient of friction. The holes were implemented to give the gasses ‘somewhere to go’. It was an effective solution, but today’s friction materials do not exhibit the same gassing out phenomenon as the early pads.

For this reason, the holes have carried over more as a design feature than a performance feature. Contrary to popular belief they don’t lower temperatures (in fact, by removing weight from the rotor, the temperatures can actually increase a little), they create stress risers allowing the rotor to crack sooner, and make a mess of brake pads – sort of like a cheese grater rubbing against them at every stop. (Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it.)

The one glaring exception here is in the rare situation where the rotors are so oversized (look at any performance motorcycle or lighter formula car) that the rotors are drilled like Swiss cheese. While the issues of stress risers and brake pad wear are still present, drilling is used to reduce the mass of the parts in spite of these concerns. Remember – nothing comes for free. If these teams switched to non-drilled rotors, they would see lower operating temperatures and longer brake pad life – at the expense of higher weight. It’s all about trade-offs.

Slotting

Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the ‘glazing’ often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

Too cool!

Last year we bought 4 rotors. Two were bone stock, and two were subjected to a process know as Cryogenically Treating – one of the high-tech buzzwords floating around the paddock. The rotors were run back-to-back on the same track on the same car on the same day with temperatures taken to make sure that they saw the same level of heat. Following the track session, the parts were removed and we had them literally dissected by a materials lab.

The testing conducted included surface hardness, grain structure analysis, density, and surface scanning with an electron microscope. Guess what – after seeing the heat of use, the rotors looked identical in every regard. This is not to say that there is not a benefit from treating other parts which see lower temperatures and/or have different material properties, but treating our rotors on our car showed no tangible benefits (note that it didn’t seem to hurt anything either). Come to your own conclusions, but in our case, we’ll pass.

Summary

So, what’s the secret recipe? Again, there is no absolute right or wrong answer, but like most modifications, there are those which appear to be well-founded and those that ‘look cool.’ If ultimate thermal performance is your goal, look to what the top teams are running (relatively large, slotted rotors). However, if ‘image’ is your thing, break out the drillpress – and be prepared to replace your brake pads on a regular basis.

Keven97SE

Hey, that actually sounds like an unbiased article from someone who knows what they're talking about?

Any way you can post the URL to that site? I'd be interested in reading any more info they have.

Thanks for the article, by the way!

MI2KSE

The exact quote was lifted from a site about (horrors!) Saturns: http://www.teamscr.com/rotors.htm This site also has a good article on braking systems in general.

There is similar information contained in a site regarding BMWs: http://www.garageboy.com/bmw/brakefaq.html

one on an NSX site: http://www.nsxprime.com/FAQ/Performance/brakes.htm

as well as one on Maximas!: http://www.geocities.com/~shinglin/car/nismo/faq.html

There is also page on SE-R.net that references a Road & Track article that I can't seem to find online: http://www.se-r.net/brakes/rotors.html

Of course, you can always just buy a fake cross-drilled rotor - much cheaper than the real thing:


As an informed consumer, I have the best brake performance upgrade for the buck - I painted my calipers red. This way, as I speed past nearsighted winos on the street, they will think I am actually driving a Porsche 911...

[Edited by MI2KSE on 12-05-2000 at 03:17 PM]

Foglght

From my personal experience being out on track with my max, I notice the brakes do fade after about 4-5 laps. Now this was full course Road America (4.0 Miles). Depending on the speeds you would see "performance driving" would determine your brake needs. One or two repeated 130mph stops from the freeway to an offramp would show some fade. If you don't get brake fade on track with your max, your not using the brakes to its MAX potential. I am currently in the market for some new rotors and pads, because the stock brakes are less than adequate for my needs. My rotos warped badly at about 30k miles. After every use on the track I had to go back to my shop and lightly grind the glaze off of my rotors and pads.
It really all depends on your driving needs. The avalon artile was very informative and right on. Most of you that were smart would take that artice at face value. If you know you don't do any track miles or whip up and down the freeway at 100+, than you probably don't need better rotors. New lines and pads would be the best option. If your going for looks, than you don't want new pads, cause the new carbon pads will make your rotor look powder coated in a day or so of normal driving (there goes the pretty look).
What the man was also saying about not getting enough heat in the brakes to get the full braking potential out of the car is also correct. The formula dodge cars I work with (I work at Skip Barber) use the brake system from a twin turbo dodge stealth. They use mintex performance friction brake pads. Now the formula cars weigh just over 1,000 pounds. In all the times I have driven those cars on track, they have never faded. With the pads that are on the car, you actually have to heat them up just to get the full braking potential out of them.
For short stints the stock maxima system is great. Your tire choice is also a factor in how fast the car will stop. Higher performance tires will allow you to brake deeper and later into a turn than with stock ones. It just all depends on what YOUR specific needs are. The article from Mr. Avalon was intended for you to understand your brake needs. There are way more uneducated people out there that "think" they know what they are doing.
This is normally is what happens to the correct information:

Person 1 that works at the high performance distributor tells person 2, the weekend SCCA racer, that this brake kit for their car is what they need. Person 2, not knowing much about brake systems, buys the kit and is very happy with results. Person 3 enters the picture as the average customer with the same car. Person 2 who actually races, but does not know all the right facts about why he needs that brake system, tells person 3 that if they want good brakes they need to get their brake system. Most of them say this because they want to sound like they know what they are talking about. Person 3 buys the same kit not consulting anybody about what they need, and is notably unsatisfied. Half the time they will go back and do all of the racing upgrades that person 2 has to their car just to try and duplicate the affect, which normally fails.

I have seen this happen more than once. The worst is when you are at a registration part of a race weekend, and everybody is drunk talking about stuff like that.

anyway, enough talking.....must go

cya
Ryan @skip barber racing

Avalon Racing

1] there is no fight. -See the comments from Ryan @ Skip Barber Racing School below.

Also note the article you reposted is from a company who sells cyro treated rotors.

We get our knowledge from experience and from brake development engineers and managers from companies who specialize in performance brake systems for track and/or street use.

Our article is for people to help them decide what system best suits there needs. As a company we constantly under sell systems if a person does not need the larger kits. This is standard prctice here.

Regards

bill99gxe

iTrader: (1)

on the cryo-treat test.

I consider this cryo-treat "test" as laughable. Woop-dee-doo, they arent' different after a day of pounding. Wow, what a thorough test. How about a year? 6 months? 2 years?, etc. That test does not conclusively say cryo-treating has no affect on long-term rotor warpage.

The basic reason for cryo-treating is to resist warpage due to heat for a LONGER period of time than a non-treated rotor. The molecular structure, when cryo-treated AND IN THEORY, will resist changes in temperature (and, thus their own structure) much better than non-treated rotors. It doesn't take a rocket scientist to understand this theory, so this method of testing is inconclusive and ignorant at best.

Like I said, this is theory, so I don't know if cryo-treating rotors REALLY do this or not. But, I've put my money where my mouth is and I'm giving them a whirl. Thus far, no warpage after a little over 4 months. I can state that these have been better than my Powerslot rotors for resistance to warpage and even regular Auto-Zone/Advanced Auto Parts brand rotors.....

I just wish people would do REAL testing instead of quickie tests when they are trying to make a point. It hurts their credibility, IMHO.