| Author | Message | ||
| Ben Cannon (Artherd)
Junior Member Username: Artherd Post Number: 194 Registered: 6-2002 |
Tip: get hose rated for small (air-cooled) airplane use, it won't MELT and CATCH FIRE like dryer hose will ;) And it'll probally only cost you $50 or so in the sizes we need. most race shops also carry this stuff (it's redish-orange and looks like (but isn't) plastic coated fabric. Best! Ben. | ||
| PSk (Psk)
Junior Member Username: Psk Post Number: 204 Registered: 11-2002 |
Brian, If your F360 has brake rotor dust/stone shields fitted I would remove them asap (unless they make a really good place to attach your cool duct), but they hide one side of the rotor from cooling air. Also reduces unsprung weight ... In my classis racing days we always found a huge improvement by removing these dust shields ... and as we do not drive on grave road surfaces, there was a very low likelihood of catching a stone in their anyway. I also agree with the others, some general purpose plastic ducting (like air box/cleaner ducting) does a perfect job ... and cable ties were designed for these sorts of racecar fixes  It must be a pipe, not just a scoop, as the air will do its best not to go where you want it unless you use a pipe. Pete | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 50 Registered: 8-2002 |
Brian, I would choose slotted discs if you have the choice. As Hubert mentioned, there is no need to buy the expensive challenge vents. You can fabricate your own very easily. The CCM brakes are likely still quite noisy. I was lucky enough to do some development work for the Enzo CCM system with a 550 M set up with the prototype system. In the early stages it was some of the worst noise I ever heard. I have not spent any time around the production Enzo, but I would expect some noise still exists in the system. As for more or less than iron... I really cant say with the Stradale 360, only because I dont know the pad configuration and compound. | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 569 Registered: 1-2002 |
Brian- You can make low buck disposable brake ducts with some : dryer hose, zipties, and, possibly, some duct tape. Just make sure its facing the center of the rotors; best thing to do would be to cut out part of your dust sheild, and attach the hose there. | ||
| Brian Kennedy (Kennedy)
Junior Member Username: Kennedy Post Number: 193 Registered: 3-2002 |
> In retaining the same size discs, drilling or slotting will > not make much difference here. Given no difference in fluid boiling, when I get new rotors this summer, should I be preferring slotted over cross-drilled (due to the other advantages)?? I won't be getting stock rotors in any case; for half the price, I can get higher temp race rotors that have the added benefit of being 1.5# lighter (each rotor). > The real solution is to get some cooling air directly onto > the disc and caliper. It is possible to develop a silicon tube > setup to the brake without modifying the car. Be sure to > direct the air into the center of the disc, where it can > ventillate outwards as intended. I hope this helps. The 360 Challenge brake ducting has been proposed for this... its ridiculously expensive... but my question is: does it do the right thing? If so, I can see about getting the equivalent fabricated some cheaper way. > If they can just find a way to make high temperature race > pads stop squealing... Oh, I'll second that. BTW, do the fancy new CCM (Carbon Ceramic) brakes, like are coming on the Stradale, squeal more or less than standard race pads on iron rotors? Brian | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 49 Registered: 8-2002 |
Brian, Glad to hear you were able to keep it off any walls. Also glad to hear of someone using a 360 as it was intended. As you are absolutely experiencing fluid boil, I think you have made the next best logical step in using SRF fluid. In retaining the same size discs, drilling or slotting will not make much difference here. The real solution is to get some cooling air directly onto the disc and caliper. It is possible to develop a silicon tube setup to the brake without modifying the car. Be sure to direct the air into the center of the disc, where it can ventillate outwards as intended. I hope this helps. Paul: the gasses that pads used to vent was the product of the resins used to hold together the pad materials. These resins would heat up and begin to burn off, developing a great deal of superheated gas in the process. The change in modern pads is just the evolution of the chemistry applied to the binding materials. As more is learned and the mad pad scientists have developed new and better techniques of combining and processing materials, as well as new chemical compounds, the materials simply do not ventillate gas any longer. If they can just find a way to make high temperature race pads stop squealing... | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 79 Registered: 12-2002 |
Most interesting thread... Eric, What is the difference in the compounds these days that causes the pad not to gas out as much as they used to - What gas was/is emitted by the pads? Thanks for all you input. Paul | ||
| Brian Kennedy (Kennedy)
Junior Member Username: Kennedy Post Number: 192 Registered: 3-2002 |
Before the Carbotech pads which have very high heat tolerance, I did evaporate the stock pads... so, yes, I know the difference in feel from pads going and fluid going. In the weeks prior to that total evaporation of one pad, I had several times gone into cool-down mode because I could feel the pads were losing it (solid feel, but much reduced stopping power... going into the dirt once). With the Carbotech pads, I have twice boiled the fluid. First time the fluid was fairly old... so I attributed it to the fluid being too wet. The pedal went to the floor... total mush... I was coming into Big Bend at Motorsport Ranch full speed (about 115)... a few pumps gave me a bit of braking... and sliding sideways as I looped it through the corner took off the rest of the speed... luckily, I stayed on track and the track was empty behind me. Second time was with the same fluid (stock) and only a few months old. Same track (I am a member there). Fortunately, due to high engine temps, I had just decided to go into cool-down mode, so I was not at full speed coming into the corner where the pedal went to mush... I was able to navigate the corner without braking much... and then just cruised without brakes around a couple more times before exiting the track without incident. Now I have put Castrol SRF in there... hopefully it will handle the heat better. | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 48 Registered: 8-2002 |
Hello Brian, Please describe for me what is happening when your brake fluid boils. I have done development work with these cars and I am curious. We have never boiled fluid. The pads will fade long before the fluid boils generally. I do not believe that the pads you are using will generate the needed temperature to boil the fluid. If you had been using a true race pad such as a Ferodo DS3000 or a Hawk Blue, these might be able to survive at temperatures above those needed to produce fluid boil. Also please tell me the circumstances around the fluid boil. Laps, what track,etc... Without knowing your level of track experience, I need to review as pad fade and fluid boil are often mis-diagnosed. If you have pad fade, the pedal will retain a solid feel and deceleration will dissipate, and even dissapear. With fluid boil, the pedal will go to the floor and be completely non responsive until it has been pumped enough to move some fresh fluid into the circuit. This is a horrifying experience on the track. If you already have fluid boil with drilled discs, then your problem is obviously heat soak. The 360 has a brake duct that feeds into the wheel well, but does not get to the brake system directly. You can fit a silicone hose from the ducting and attach it with hose clamps to a suspension arm for example and direct the airflow onto the disc and caliper directly. Just recently we were lucky enough to be invited by Chris Parr to develop some track worthy brakes for his F40, and in doing so made the mistake of only finding out at the track event he had planned that the master cylinder had a bad seal, which produced similar symptoms as fluid boil. Eventually it all worked out for the best. But it taught us a lesson in development here. | ||
| Brian Kennedy (Kennedy)
Junior Member Username: Kennedy Post Number: 190 Registered: 3-2002 |
Eric, Thanks for joining in. As I will likely run through my 360's rotors sometime this summer, this discussion is very interesting to me. I have the standard cross-drilled rotors... sounds like I should consider slotted. However, I suppose my criteria might be a little different: 1) I have had issues with boiling the brake fluid; so if the cross-drilled cool better, that might be an advantage, even if less than the performance ideal; 2) I am too lazy to switch the pads every week (I try to go to the track weekly); so, I just drive with my track pads on the street (I choose track pads with reasonable cold performance; currently Carbotech Panther Plus). Question #1: Will slotted rotors tend to be more or less noisy than cross-drilled with track pads? Question #2: Will slotted rotors tend to heat the brake fluid more or less than cross-drilled? Thanks!! Brian | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 47 Registered: 8-2002 |
Hubert, thanks for the link. The article was from some years ago, and most all of the concepts of the paper have found their way into ABS software. As the different companies whom develop ABS systems (Bosch, Teves,etc..)all use proprietary software and design, I am not sure to what degree or type of computing is happening currently with these systems. They are also integrated currently with vehicle stability and/or traction control, which adds a whole new wrinkle to the subject. Everybody is right in the speculations about F1 braking systems. Mclaren tried to control the braking L/R with a split pedal, and the driver would trail brake by rolling to the inside brakes only to get the car turned in, which allowed for a chassis setup that would normally understeer more but allows power to be applied earlier in corner exit. It was banned. The other innovations probably happened, but much about F1 is speculation, and the other half rumor. Most everything imaginable and not imaginable has been tried at some point. | ||
| James Glickenhaus (Napolis)
Member Username: Napolis Post Number: 657 Registered: 10-2002 |
Pete I think this involved a split brake pedal. The left foot braked the left side brakes and the right side braked the right side brakes. Clutch was on steering wheel. It was banned. Best Jim | ||
| PSk (Psk)
Junior Member Username: Psk Post Number: 190 Registered: 11-2002 |
Hugh, Didn't McLaren also have a system (might not have been at the same time) that braked the car harder on the inside and thus helped pull the car into the corner? I believe this was banned also ... as it involved some sort of computer control. Pete | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 567 Registered: 1-2002 |
Eric- Did you ever read about the trick McLaren used to get around traction control bans in Hakkinens '99 car ( I think). Essentially, they had a lever that allowed Mika to apply greater braking force to the wheels that were slipping. Clever idea. Fuzzy logic, lately, has been pushing the forward development of all road car aids. Here is a blurb, published by intel, on fuzzy and it's interface w/ ABS: http://www.intel.com/design/mcs96/designex/2351.htm regards, hubert | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 46 Registered: 8-2002 |
Most race series are banning ABS to keep the braking function up to the drivers input (skill). It is also a method of controlling costs, as adding ABS adds yet another computer controlled variable to the system which could spill over into traction control, etc... This variable would be exploited by teams with larger budgets vs those without, as is always the case in racing. I dont think there was ever a time when brakes were incapable of locking full slick tires. Brakes have always had more power to stop the wheels than there was available traction from the tire in racing. It is actually been developments in tire compound and construction that have kept racing cars going continually faster and with higher traction budgets. it was the advent of aero downforce that really pushed tire design forward. The issue is simply that it should be up to the driver to hold the tire on the edge of available traction as opposed to a computer. The ability to tune ABS would be staggering, it could be tuned to brake each wheel differently, and in sequence, it could recognize track position and function automatically, etc..In as much safety as it adds to a road car, it would detract from auto racing as a skill. | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 565 Registered: 1-2002 |
Rob- It is my understanding that, in a majority of the series, ABS is illegal. ABS systems, essntially, allow the driver to threshold brake w/out having the skill to modulate the brake pedal, and keep it at the edge of lock up manually. | ||
| Rob Lay (Rob328gts)
Board Administrator Username: Rob328gts Post Number: 3752 Registered: 12-2000 |
Are ABS systems so important in race cars now because the brake technology has increased to the point where even full race slicks break friction under heavy braking? | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 45 Registered: 8-2002 |
In years of testing, it has been found that the actual size and shape of the pad is for the most part, irrelevant. The important factor is the Cf of the pad. piston size is critical, as line pressure is distributed equally across the piston surface, and the area of the piston multiplied by the pad cf basically dictates a clamping force. This force is then simply related to the length of the effective radius from piston centerline to axle center as a lever arm. This torque is then applicable as a tool to compare the sytem at given line pressures and pad Cf(also pad Cf changes with temperature)at a given snapshot of system operation. This can be used to calculate the braking system abilities and f/r balance. pad size and shaping is more a product of heat characteristics. Highly specific racing calipers are limited in amount of disc surface area and other factors which dictate that a pad may need to be very long for example, and would require a higher number of caliper pistons to apply even force across the pad. There are hundreds of standard pad shapes. There are many formulas for determining how much pad area is required for a given heat index that a vehicle will be subject to. This is a starting point for braking system development Braking torque is essentially the power of the braking system, and is defined as (Piston Area) x (Effective Radius) x (Line Pressure) x (Brake Pad Coefficient of Friction). Piston area is wholly dependent on the caliper, and the effective radius is a result of the caliper and disc combination. We express the result in Newton Meters, and comparisons must be made at the same line pressures. Pad Cf is considered unitless for this calculation. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 2498 Registered: 6-2001 |
Eric, that was very informative. I didnt realize that it was the piston area, not the pad area, that made the difference. Why is it that way? edit- i think i just made the connection in my head. There is a torque perpendicular to the plane of the rotor coming out of the plane of the rotor because the torque is a vector product of the length of the moment arm and the force applied to the moment arm. what does this have to do with it? | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 44 Registered: 8-2002 |
Hello Ron, We offer a system for the 308 model, 1977-1984. I do not know if your car has knuckle and hub changes from this model. The easiest way to find out is to contact Carobu Engineering,949-722-9307, who is a retail dealer for us in California and a Ferrari specialist. They will know far more about model year changes than I about the 308 series. Brembo brakes were never fited OE to the 308, so we do not have drawings or complete information for that model. | ||
| Ron Shirley (Easy_rider)
Junior Member Username: Easy_rider Post Number: 238 Registered: 12-2002 |
Eric, I see on the Brembo site that the listings for Ferraris are for 348's and 355's. Do you make any systems that will fit a 1987 Mondial 3.2? | ||
| Eric Dahl (Brembo)
New member Username: Brembo Post Number: 43 Registered: 8-2002 |
Gentlemen, For those who don't know me, I am an engineer with Brembo NA. Most of you have made some strong and real points in this discussion. Let me make a couple of points: Slotting discs is used widely in sportscar, GT, and Rally racing as it does "shave" and refresh the pad surface continually. Drilled discs are not really used in racing anymore as they cool too quickly and do not allow modern race pads to operate at the temperatures the function best at. An argument was made by Hubert earlier that says that if drilled discs were better that they would be on F1 cars. This would be valid if F1 cars were using iron discs. They are using carbon discs and pads. The functional dynamics of this system is worlds apart from standard iron disc systems. If F1 cars required iron discs, you would see F1 teams trying to keep the discs cool any way possible. Apples and Oranges. Almost nothing in F1 translates to road cars. Drilling discs does reduce disc mass, however this does not affect the braking torque, or the "swept area" (swept area is a measurement of pad surface area). Friction surface is the measure of the disc area in contact with the pad. Braking torque is a calculation based on system pressure, piston diameter, and effective radius as well as pad coefficient. Removing material by drilling reduces the heat index of the disc, or the ability to retain heat. The disc gains in the ability to shed heat however. So there is a trade off in values there. For road car sport driving, this trade off is perfectly acceptable. It can also be desireable in terms of disc life. In the world of racing, a disc should be able to retain enough heat to keep the pads at effective temperature, as I mentioned before. Pad fade is the most common problem with hard driven street cars. Upgrading to a higher performance pad is desirable for track events, but the tradeoff to that is increased noise and significantly reduced disc life. This is a fence that all manufacturers walk on. Even Ferari has to consider that it's customers will expect high performance, but will not tolerate high noise levels or replacing discs every 6 months (especially at $600 per disc) The final note is that drilling and slotting is to some degree a design issue. Both are associated with high performance braking systems. Manufacturers generally use drilling as an added asthetic feature first, and a performance feature second. Slotting is a higher performance option in that it can be used with race type pads, and is still in use with several different types of racing. I am not aware of any manufacturers currently offerinf slotted discs as standard items. | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 564 Registered: 1-2002 |
Mitch- I made my comments regarding braking system iprovements with the assumption that everyone realized that the tires stop the car, and that the brakes are mearly a medium of exchange; i.e. kinetic for thermal. Therfore, to reduce fade (thermal stress, if you will), you need to make the system more thermally efficent. YOu will only gain leverage on the system by moving the caliper further out, you accomplish this by using a larger rotor. Torque = force x distance; therefore, bigger is still better, but I'm not sure I'm reading your comments correctly. mike308- Cross drilled rotors were used, primarily, at a time when engineers wanted to reduce rotatating mass, but did not have available to them the exotic materials and metallurgy available now. However, this application is still used with the same purpose in applications where the use of exotic materials is cost prohibitive; i.e. motorcycles, etc. The use of drilled rotors on street cars, was, for all intents and purposes, an aesthetic one Rob Lay- If I remember correctly, the challenge drivers petitioned FNA to change the spec rotors to something non drilled. Some one correct me please. | ||
| Chris Parr (Cmparrf40)
Member Username: Cmparrf40 Post Number: 562 Registered: 3-2002 |
Drilled rotors are fine for the street, what we are talking about is maximum brakes for the track. Drilled looks cool, and is fine for the way most people drive. But when you need maximum braking, solid is the way to go. | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 282 Registered: 11-2002 |
Mitch, "leverage" relating to brakes is commonly reffered to as brake torque, measured in Ft-Lb of force, just like an engine. And I agree with you. One can calculate it easily, too. Brake Handbook, by Fred Puhn. Excellent reading. | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 281 Registered: 11-2002 |
Rob you're right the 355Challenge OEM's are indeed drilled. This is why I recommended in your 355 Challenge thread not to use drilled. You'll play connect the dots and spend cash. Go with the slotted, more life out of the equipment. Drilled rotors on a road car are mainly a marketing decision. IME, one cannot make a blanket statement covering all engineering environments, though IMO, the slotted vs. drilled debate comes close. I generally recommend slotting for virtually all applications. But this is because most production based brake systems are barely adequate for high performance use, let alone track. Drilled rotors will always have a proper place in improving a brake systems performance, but the designing engineer will take the vehicle's entire system and operating environment into consideration first. BTW, I can see why one would want to upgrade Suburban brakes. I crested the Appalachian's too fast while pulling a 28,000 lb goose neck trailer in a dually once. Just once. | ||
| mike 308 (Concorde)
Junior Member Username: Concorde Post Number: 126 Registered: 8-2002 |
Hubert has a lot of points against cross-drilled rotors. But then I guess Ferrari has had it wrong all these years, since in looking at the www.FerrariUSA.com site they are factory installed on 360's, 575M, 550, F50, 512TR... and yes they're also on the 355 Challenge racecars. I guess the Ferrari engineers just didn't know who to ask for advice! | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 359 Registered: 4-2002 |
I disagree with hubert on two points on statement 1: Bigger brakes can stop faster because of more leverage--but only if the tires can retain their grip on the road. Since most brakes are capable of locking the tires (without ABS) bigger brakes dont allow more force to be applied at the road surface. Bigger brakes can absorb more heat (energy) before they get too hot (temperature). And bigger brakes have more leverage on the wheel/tire combo, lessening the pressure required to lock the tires. | ||
| mike 308 (Concorde)
Junior Member Username: Concorde Post Number: 125 Registered: 8-2002 |
Even the Enzo has rotors with holes. Whether they're drilled or cast, I don't know. The material isn't steel, though. | ||
| Rob Lay (Rob328gts)
Board Administrator Username: Rob328gts Post Number: 3741 Registered: 12-2000 |
If I remember right the 355 Challenge has cross drilled rotors. Was this a fad a few years ago that they've just now figured out makes things worse than better? I believe they are Brembo rotors. | ||
| Chris Parr (Cmparrf40)
Member Username: Cmparrf40 Post Number: 561 Registered: 3-2002 |
Hugh, are arguments sound compatible! Drilled rotors are not the best choice, a solid rotor , properly vented provides maximum braking performance. Slotted rotors have NO effect on cooling but maximize breaking performance by "cutting" a clean edge on the pad reducing the effects of "glassing". I think we agree on more than we disagree on! In re-reading your earlier comments, and with a fresher brain (long day yesterday!) in fact I think I am in complete agreements with your comments! I just learned the hard way that F40 brakes suck! Now I have a system that actually stops the car and does not require constant attention. Thanks for your comments! Chris | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 562 Registered: 1-2002 |
Chris- Friction between the pad and rotor is what causes you to stop. Heat is a bad thing; bad for the rotors but it is a lot worse for the pads. A warped rotor will still stop the car - it will just feel like crap. Overheated pads however WILL NOT stop the car. It is here where the rotors secondary responsibility comes in. Its job now is to DISSIPATE the heat away from the pads and DISPERSE it through itself. Once the heat is removed from the pad/surface area it is then removed. Notice where the removal falls on the list of duties? number 3. #1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle #2 DISSIPATE the heat #3 REMOVE the heat from the brake system In-depth: #1 Maintains a coefficient of friction with the pad to slow the forward inertia of the vehicle: The rotor's surface is where the pads contact and generate friction to slow the vehicle down. Since it is this friction that causes the conversion of forward acceleration into deceleration (negative acceleration if you will) you ideally want as much as possible right? The more friction you have the better your stopping will be. This is reason #1 why BIGGER brakes are the best way to improve a vehicle's stopping ability. More surface area on the pad and the rotor = more friction = better stopping. #2 DISSIPATE The Heat: Let's assume for a second that the vehicle in question is running with Hawk Blue pads on it. The brand doesn't really matter but that is what I am using as my example. They have an operating range of 400 degrees to 1100 degrees. Once they exceed that 1100 degree mark they fade from overheating. The pad material gets too soft to work effectively - glazing occurs. This means that a layer of crude glass forms on the surface of the pad. As we all know glass is very smooth and very hard. It doesn't have a very high coefficient of friction. This is bad - especially when I am coming down the back straight at 125MPH. Lucky for us the rotor has a job to do here as well. The rotor, by way of thermal tranfer DISSIPATES the heat throughout itself. This DISSIPATION lessens the amount of heat at the contact area because it is diluted throughout the whole rotor. The bigger the rotor the better here as well. The more metal it has the more metal the heat can be diluted into. #3 REMOVE the heat from the brake system: This is the step where the rotor takes the heat it DISSIPATED from the pads and gets rid of it for good. How does it do this? By radiating it to the surface - either the faces or inside the veins. It is here where cool air interacts with the hot metal to cool it off and remove the heat. Once again there is a reoccuring theme of "the bigger the better" here. The bigger the rotor, the more surface area it will have which means more contact with the cooling air surrounding it. Why cross-drilling is a bad idea. First - as we have already established, cross-drilling was never done to aid in cooling. Its purpose was to remove the worn away pad material so that the surfaces remained clean. As we all know this doesn't have much of a purpose nowadays. Next - In terms of cooling: Yes - x-drilling does create more areas for air to go through but remember - this is step 3 on the list of tasks. Let's look at how this affects steps 1 and 2. The drilling of the rotor removes material from the unit. This removal means less surface area for generating surface friction as well as less material to accept the DISSIPATED heat that was generated by the friction. Now because of this I want to optimize step one and 2 since those are the immediate needs. If it takes longer for the rotor to get rid of the heat it is ok. You will have a straight at some point where you can rest the brakes and let your cooling ducts do their job. My PRIMARY concern is making sure that my car slows down at the end of the straight. This means that the rotor needs to have as much surface as possible to generate as much friction as possible and it needs to DISSIPATE the resulting heat AWAY from the pads as quick as possible so they continue to work. In both cases x-drilling does nothing to help the cause. Now let's talk about strength - and how x-drilled rotors lack it. This one is simple. I don't know how drilling away material/structure from a CAST product DOES NOT weaken it? Thermodynamically, what happens to a cast iron molecule, when it is overheated - the covalence bonds weaken. These bonds are what hold the molecules together, this leads up to fractures. So why don't race teams use them if they are so much better? Consistency? It is because of several factors. They are as follows but in no particular order: - Less usable surface area for generating friction - Less material to DISSIPATE the heat away from the pads - Less reliable and they are a safety risk because of fatigue and stress resulting from the reduced material Regarding slotted rotors. Any time you modify a cast rotor, you weaken it. They are less prone to cracking than drilled rotors, but more so than OEM rotors. All the same arguments apply. The only legitamate use of slotted rotors that comes to mind is rallye cars, where the slots serve to clean dirt/dust off the braking surfaces. However, most slotted rotors I've seen on track quickly fill up with brake pad residue, rendering the slots useless. Just my wortheless opinion. | ||
| Chris Parr (Cmparrf40)
Member Username: Cmparrf40 Post Number: 560 Registered: 3-2002 |
Hugh, your theory as you call it sounds great, it is wrong, but it sounds great! PSK is right, slotted disc deglaze or cut a new breaking surface on the pad with every rotation. Only the leading edge of the pad generates breaking force, this is why you see multiple pads or cut pads on calipers. The intent of drilling was origionally designed to allow gasses to escape, this is no longer an issue. The biggest negative of drilled rotors is they run too cool. Heat creates friction, friction stops the car. Controlled heat is a good thing. Drilled rotors heat up during the braking process but immediatly cool down after the braking area, thus you must heat them again to during the next braking process. This heat up and cool down process increases braking efforts and destroys rotors. Slotted disc have more mass, they retain heat more evenly, creating more friction and improves braking performance. Crossdrilled brakes looks great, but they are not the best choice in performance brakes. For more information on slotted disc's please read the December 2002 issue of Forza, the article on Brembo brakes upgrade on F40's will help you understand why slotted disc's are best and a slow reduction in cooling is best for braking. I guess I must confess, I learned from the best, I had the benefit of Eric and Mark from Brembo to design a one-off system on my F40. Brembo had my F40 for 3 months developing the best brake system available, short of a carbon set-up. Oh, and as we learned, you better replace the masters cylinders too! | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 560 Registered: 1-2002 |
Tim - Not true. Reducing the surface area of the rotor by drilling/slotting reduces swept area; less swept area, more braking force. It's real, believe me. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 2492 Registered: 6-2001 |
Hugh, force against the rotor is unchanged even if you have more holes. This loss in surface area is a loss of area that the pad and the rotor can create friction with. Smaller area+same pressure= less braking force because of less contact area. | ||
| PSk (Psk)
Junior Member Username: Psk Post Number: 186 Registered: 11-2002 |
Hubert, While I agree with 100% regarding racing applications, and carbon rotors regarding hole drilling and slotting, I do believe that for a street application that the slotting of the rotor has some use. Brake pads which are used for boring road applications do glaze. You notice this when you replace your 30,000 km old pads with nice new pads and just about stand the car on its nose with the first few tests before you re-adjust your brain . Thus in this application I believe the slotted rotors would help maintain a better pad for longer. Again the holes, would suit a road application or a less expensive application, where the best materials are not available ... like you state for a motor bike. Thus I would have thought that Ferrari road cars would benefit from this too, as most see little track action. Anyway ... they look good , okay only joking ... performance is far more important than looks Pete | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 559 Registered: 1-2002 |
PSK- My swept area thory, is only part of the equation. Goes something like this: when you remove surface area, you remove swept area, and increase braking force; as in, same pressure + less area = more force. However, this is only a temporary upshot, because, the pedal response becomes grabby, and non-linear. Removing material out of a rotor is bad, b/c you weaken the rotors ability to effiecntly dissapate heat, and provide it with less material to do so; hence the premature warping of discs (both drilled, and slotted; i've tried both, and have warped both faster than full face rotors. In a track only application.) All drilled rotors crack, and if you really pound on them, so will full face rotors, but they will do so after a longer interval. Heat IS the cause of fade. Dissipation of that heat, efficently, is the primary purpose of the brakes. The more material your brakes have, and the more efficently they are able to tolerate it, the less they will fade. That is why many swear by cryo treating rotors; it's makes them more 'thermally' efficent. That is also why, most sports cars have huge rotors. The best way to reduce fade is to increase the size of the rotors. Cross-drilling, initially, was used on applications where rotating mass was to be limited, but the materials were not up to par, so, the maufacture swiss cheesed the rotors, easy enough. This is still used on motorcycles, where the use of exotic materials to reduce weight is cost prohibitive. This point is made clear when you look at F1 carbon systems, the disks are full face. No x-drilling. No slotting. If drilled rotors were better, in any way, they would surely be on F1 cars. The 4 pad design, and multi piston caliper setup, is not only meant to improve modulation (in non-ABS setups to allow for safer threshold braking), but also to reduce brake pad taper. The 916's, 748's, and 998's all had this setup. | ||
| PSk (Psk)
Junior Member Username: Psk Post Number: 184 Registered: 11-2002 |
Hubert,
My pads were not glazing, especially after I changed after doing some heat tests, but this was what I was told the slots were for (and repeated in the sales brochure) when I purchased the rotors, infact I had not ordered the rotors with the slots ... but that was all they had left unless I wanted to wait for the next shipment. Cannot remember the brand now but an American brand I think. I do agree with you though and maybe the slots do this deglazing (thanks for the spell check ) for road applications. While I understand your swept area theory, I do not believe that is the main or original reason for drilling or slotting ... I could be wrong, but surely cooling and lightening the rotor + deglazing (in road applications) is the first intention. It is interesting to note that the new Brembo calipers and pads used on the latest Ducati 999 have 4 small pads per caliper instead of 2 large ... this I guess would be to increase the pressure per swept area like you state and allow the smaller pads to follow the rotor surface better. I have just read the Brembo site information and here is what they say: Why use drilled or slotted discs? Drilling or slotting discs aids the disc in several ways: The edges of the slots or holes continuously clean and refresh the pad surface as well as providing increased brake "bite". Additionally, they prevent gasses from collecting between the pad and disc interface. The disc is lightened, thereby decreasing its rotational inertia. Improved ventilation increases the disc's ability to shed heat, resulting in cooler operating temperatures What are the advantages of drilled and slotted discs? The main advantages of drilled and slotted discs are the same: increased brake "bite", and a continuous refreshing of the brake pad surface. Drilled discs have the additional advantage of being lighter and running cooler. However, there are certain pad materials that should not be used with a drilled disc. There ya go ... they do mention bite, which sounds like the same as your swept area theory ... and cooling and all. Refreshing the pad surface is what I call deglazing. Oh well I have learnt something Pete | ||
| Erik Smith (Teenferrarifan)
New member Username: Teenferrarifan Post Number: 6 Registered: 2-2003 |
The real reason i installed slotted rotors and had my calipers painted yellow was to make them sort of contrast with my 20 inch rims. The stock gray calipers and stock discs just didn't stand out enough for me. So that's the real reason i got them. erik | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 73 Registered: 12-2002 |
http://hp.brembo.com/edit/faq/index.asp?ECSShopperID=76ELG9HE33058N6T6MB01W42CVB74CA9&LngCode=ENG&sCurrency=USD&PrCatID=3#22 Even more information! | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 557 Registered: 1-2002 |
PSK- Drilling and slotting decreases swept area, and propotionally increase breaking force, as I pointed out: smaller area + same pressure = greater braking force. If your pads are glazing, then they are overheating, and you're using the wrong compound for the application. | ||
| PSk (Psk)
Junior Member Username: Psk Post Number: 182 Registered: 11-2002 |
Hmmm, Slotted rotors are used to deglase the pad surface ... not sure what you guys mean with outgassing. Pads can when they get hot can glase and thus become less effective. The slot in the rotor wears the surface off the pad, effectively deglasing them and thus maintaining their condition. Drilled rotors are simply drilled to increase the surface area for cooling and to lighten the unsprung weight. Obviously the hole has the circumference to help with cooling ... same as ventilated rotors which do a much better job. Naturally a hole will allow the air to travel around the rotor better. I have used slotted rotors on race cars, but not drilled and they work great ... but yes you do have to check for cracks, but you should always check any rotor for wear and cracks anyway (assuming you actually drive your car ) I have never heard of a crack starting from a hole in a rotor ... interesting as they drill holes in the end of cracks on aircraft to stop the crack spreading ... Pete ps: In my opinion a standard Porsche 911 has better brakes than a standard Ferrari equivalent. Porsche drill their rotors ... | ||
| Hubert Otlik (Hugh)
Member Username: Hugh Post Number: 556 Registered: 1-2002 |
Guys- Gassing out of pads is no longer as grave an issue as it once was. Pad materials have changed, considerably, and the gassing out is no longer the problem. The proverbial problem with brake fade is: HEAT. Slotting and/or drilling reduces swept area; as you decrease the swept area (all else equal) you increase the braking force. You have the same pressure applied, but over a smaller area, so the result is more pounds per square inch. It will wear the pad faster, but actually increases the braking force unless the pad overheats. Reducing the swept area does make the brake action grabbier. But more importantly taking mass out of the rotor decreases the thermal capacity of the rotor. Heating the pads beyond their operation range (at which point their coefficient of friction goes south), boiling the brake fluid, and rotor warpage are the brake killers. That's why in the end the only really effective brake upgrade is a larger diameter and/or thicker rotor. You can use a pad material that can stand the heat but the thermal capacity of stock sized rotor on almost any production car is sadly lacking. Full faced rotors are the way to go, but it does not produce more braking force. It does give you the maximum thermal capacity. People that want to sell slotted or drilled rotors play up the importance of gassing. Heat is the real killer. Full face rotors are not only cheaper, but have more metal in them to cope with the heat. Pad choice will determine how consistant the brakes are at high temp, not rotor choice. $30 brembo full face blanks, good pads/fluid, and buy another set of brembos when they get too warped to stand. (they will if you are using them hard). The slotted or drilled rotor will warp up even faster, especially if you use some pads that don't fade (like ebc red, hawk, porterfield, etc. - hubert | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 2491 Registered: 6-2001 |
Slotted rotors are still better on the ROAD. You might like them for looks, but that would make you a ricer. If you pic looks over function, you could be a ricer. y0 the ride would look phat with some of those ill cross drilled pieces. | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 354 Registered: 4-2002 |
Because Ferraris are ROAD cars. | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 71 Registered: 12-2002 |
Tim, I should have posted a bit more than �interesting link� � There was no talk about green-pad-fade or outgassing related to the slots/drillings. - that�s what I thought was interesting!! | ||
| Martin - Cavallino Motors (Miami348ts)
Advanced Member Username: Miami348ts Post Number: 3901 Registered: 5-2001 |
Love it Paul! ah modern technology! Will I ever learn to work with publisher. Dude, I just got a Dell. (still sitting in the box) | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 2489 Registered: 6-2001 |
That article is wrong. Just because a car can lock its tires doesnt mean it can't improve stoppping distances without puting on better tires. My friend has a 74 nova that had 4 wheel drums. It could lock them up, but it couldt stop worth sh*t. now with front wheel discs there is a huge difference. stopping distance is limited by the ability to modulate the braking force to keep the tires on the verge of locking up. It is also wrong because the holes and slots are not there to cool the pads. they are there for outgassing. | ||
| Tim N (Timn88)
Intermediate Member Username: Timn88 Post Number: 2488 Registered: 6-2001 |
Theres also less surface area with cross drilled rotors for the pads to make contact with. Back in the 60's when pads produced alot of gas, i can see why they would help. Slotted rotors are capable of outgassing good enough, and are stronger. This is why you see them on race cars instead of cross drilled rotors. | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 70 Registered: 12-2002 |
Interesting link http://www.lambolounge.com/Chassis/Front-end/Brakes/brakes-ft.htm Paul | ||
| Mr. Doody (Doody)
Member Username: Doody Post Number: 817 Registered: 11-2001 |
BTW are you still a redneck if you tow your house with a Ferrari? ROTFLMFAO! doody. | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 69 Registered: 12-2002 |
Drilled rotors (cast) are susceptible to cracking as the drilling causes a weak point around the hole. I remember seeing somewhere that Porsche started to cast the holes into the rotors so that the grain flow went around the hole. Paul | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 396 Registered: 6-2002 |
My homework suggests that drilled or slotted rotors provide a pleasing experience for the eye, and little else. They do disrupt the metal surface exposing a nidus for cracks to form. They do not lighten significantly, and they do not cool sufficiently to provide benefit. The only benefit is related to water - the slots or grooves provide an exit route to minimize fade while wet. Give me all the surface area I can have. Jim S. | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 68 Registered: 12-2002 |
You want one??   | ||
| Martin - Cavallino Motors (Miami348ts)
Advanced Member Username: Miami348ts Post Number: 3894 Registered: 5-2001 |
towing a house with a Ferrari???? how, I checked with U-Haul and they do not have hitches for my 348. Anybody any hitch leads? BTW are you still a redneck if you tow your house with a Ferrari?  | ||
| Matt Karson (Squidracing)
Member Username: Squidracing Post Number: 419 Registered: 3-2001 |
Towing a house. | ||
| Paul Hill (348paul)
Junior Member Username: 348paul Post Number: 67 Registered: 12-2002 |
and downhill !! | ||
| david handa (Davehanda)
Member Username: Davehanda Post Number: 523 Registered: 5-2001 |
Towing I would presume... | ||
| Mr. Doody (Doody)
Member Username: Doody Post Number: 815 Registered: 11-2001 |
what exactly are you doing in your suburban that you can get the brakes to fade enough to warrant replacing them? just curious! doody. | ||
| Erik Smith (Teenferrarifan)
New member Username: Teenferrarifan Post Number: 4 Registered: 2-2003 |
How come Ferrari uses crossdrilled but not slotted brakes? Isn't it true that slotted offer just as much fade resistence as drilled and are stronger. The only advantage would be drilled are lighter but aren't they weaker as well? Just wondering what people think about the issue. I installed slotted rotors on my suburban and noticed a noticable decrease in fade. erik |