mklaskin

Mark,

I'm not trying to be an internet tough guy, but you do bring this on yourself. These guys are offering solid advice, based on experience and trial and error and you're quick to reject it.

Veloce Raptor

..

Bernie930

WOW, 11 pages of 928 kibort bull****, surprised it lasted this long,lol.

KaiB

HOLY COW MARK...

Six pages ago I told you about an air cooled car at well over 2700# which runs .31s all day long on 322mm front rotors without any problems at all.

Ain't the rotor.

mark kibort

And i asked how much power....... this is a key question, and after all the information posted, you should know why. do you?

I also have HAD, (before my hp ugrades) a competitor that runs the 13" rotors that had no brake fade, and actually, ive driven the car and it felt much better than mine. But, the reason, was it had much less KE than mind being 300lbs lighter. same lap times, and same speed down the main straight. What he was doing different than I was, even though both of our cars at the time were within the brake system capability, was a lot of ducted cooling to the brakes

Hey, im listening, taking notes, and planning my next mods

Questioning and analyzing is part of the racing game. it gets you smarter.
believe it or not, i do have quite a bit of experience in this technology as well. I dont think you can discount my assumptions or calculations as easy as you have. ive seen a TON of guys, do what the experts have told them to do, only to have it not work at the track. Ive helped some of these guys to get faster and have their cars be more reliable.

KaiB

Just noticed this. You clearly have issues which should be addressed.

Done with you forever, not that would matter to you at all.

mark kibort

You are being an internet though-guy. Insults are not a way to discuss a topic. its juvenile. I wouldnt do it to you or anyone , but yet you think its ok? And my analysis isnt solid? what gives their advice more weight than my questions. When advice is given, and the foundation for the logic is flawed at the foundation, dont I have enough knowledge and experience to question it? I mean, com'mon. I have slightly unique problem. brake pad overheating during only a very unique portion of a track and no other place or at any other track.
Isnt it remotely possible that I could be exceeding the components? if not, im listening. The logic i use is good ole physics. Many have commented and misquoted or used the equations incorrectly and have not even come back to admit their errors, making much of the discussion one way.

Look, its simple i have a brake overheating issue. cooling is the issue and that can come in two forms. Larger rotor or better brake ducting.
Im installing the brake ducts tomorrow and bias bar next week, based on the discussion here. BUT, i was trying to discuss my doubts, but no one wants to talk about it, because of their experience. Most commonly, I see and hear, is cooling problems due to braking technique or boiling fluid. The first can be fixed by technique, the second can be fixed by ducting. I feel because of the tests ive done, that the problem is in a very narrow window and I dont think that air flow can remove enough heat at the end of the straight. (its a feeling, not fact. just a question for which i havent heard any factual information)

brake bias was the other suggestion, but i dont feel (again, not fact )that more rear bias and the capability of the rears can slow the car so much faster that the lesser time of threshold braking up front, will slow the car before the fading heat is generated. remember, if im using the brakes to the limit of the front tires, the rears must make a significant contribution and some calculations just dont see thats possible. but, again, i could be wrong here, but looking to discuss.

I mentioned larger rotors , that have 15%-20% more torque for the same pedal pressure, or 15% less pressure for the same stopping force. The KE is the same to get to the turn in speed, but the heat is able to be dissipated in the 15%-20% larger diameter rotor, plus it also have 15-20% more surface area and mass at the rotor contact area, but that idea was dismissed.
Personally, i think this is the easiest and best way to solve the problem and gives more margin for greater HP upgrades down the road.

Ive discounted suggestions that going lighter is not a solution, as for the same reason it allows for greater turn in speed, it allows for greater comparitive top speed down any straight before braking. For this reason, the KE is near the same and is not a solution (but again, those that suggested it, havent double checked their work.....If im wrong there , love to hear about it, but i dont think that i am.) Anyway, that part of the discussion is just that. i cant drop any more weight, significant anyway, whicih would help lap times but wouldnt do a damn thing for solving a braking overheat problem in the area of the track im discussing.
But make no mistake, those kind of intuitive suggestions are not correct. KE is KE. you cant fool James Watt, or the laws of thermodynamics.
Most of the responses have come from the completely wrong direction. lower the weight, would absolutely fix the probem, if you didnt have the same KE to start with.... meaning, if you had the same top speed before braking, absolutely, they would be right, but thats no where near the reality of the suggestion. all the Hp vs time suggestions, have left out key elelments of their arguments. its NET FORCE (or net power) folks, not just how long your 300rwhp car was putting down 300rwhp..... thats just sillly....... yet, no one comes back to admit the flaws in thinking!

mklaskin

Sorry if I offended you. Often times you post questions here, get good answers and then tell other that they're wrong, without proving how or why. And by proving, I mean actually applying the suggestions and returning with results.

If you have an overheating issue at one point on one track, and no where else, it sounds like a technique issue.

My first race car, a Kelly-Moss built RSR (KMR-RSR 001) had 993 twin turbo "big reds", with ABS and a 3.8 liter making +/- 380 at the flywheel. It did not have a bias ****. With me in the car, it weighed in around 2750#'s. That car, in 90 degree heat and high humidity did not have fade issues. So I do not agree with your KE assessments. They were state of the art brakes when the 993 Turbo was in production, and were excellent with a lighter car, going much, much faster, repeatedly, with greater forces in every way.

Lastly, look at every competitive road racing car. They will all have the largest rotors allowed, or necessary for a given circuit, will have the largest ducting allowed (again, may vary by circuit) and be as light as possible.

Best of luck.

mark kibort

Matt, in the typical form of the internet bullies, or know-it-alls, i would expect more from you. You seem like a smart guy. Now, read my response to Mike. yes, ive listened and read EVERYTHING everyone has wrote and suggested. alll good stuff. the reason its a discussion, is that i want to solve the problem by understanding it, so i choose the right one! Just what if, ive exceeded the capabilities of the 12.6" rotor, the clamping force, and the pad friction based on the KE we are trying to dissipate?? Just what if?? others have chimed in with saying others are doing it, but i havent seen it. sure, there are LOTs of fast cars running lots of HP running 13" rotors and running 1:31s at laguna, but they have a lot better HP/weight
you see, it also is just more than KE change, its rate of KE change. If i get to 160mph down the straight, vs my 130mph before braking, but the 160mph car brakes at nearly double the stopping distance and applies the brakes for twice as long, the heat is much more managable and lap times will be much faster. You see this all the time with big HP cars. I remember running up to the back of some of the world challenge GT cars on TV in the braking zones, hang around the turns, only to get smoked down the straights!

so, as i said many times. im installing ducts and doubling the brake bias. dont know if that is the answer, but certainly worth a try.

now, if you take your comparison of "train vs motorcycle" to a physics instructor you might understand better.
Im trying to explain it in the most simple terms. KE is made up of mass and speed, thats it. slowing the car exchanges KE (energy) with heat (energy). its a direct exchange (minus aero force, rolling/ component friction, and compression braking force). Lets just call it even with heat.

if you are 3000lbs and you want to get from 120mph to 60mph it will require that x (KE) is generated in heat at the rotors. if you want to lose weight and run 2700lbs from 125 to 60mph, you will be releasing the same amount of energy in heat. (i posted the KE values for both).
Its actually much more complicated than this, because we have to look at decel rates (the rate of change of KE, which is power.....and i know how VR loves power.... but we can do it in Ft-lbs too. The greater the decel rate, the greater the HP and heat required to slow the car. (just like accelerating the car, is proportionate to power, as seen with acceleration= power/(mass velocity) . The energy is the HP-seconds. So, two cars with the same KE slowing to the same KE, will dissipate the same heat. But, the faster its done, the greater the thermal load on the brake rotors. so, its possible, that the lighter car can slow the car proportioally faster than its lighter weight, and create more of a thermal load on the rotor that doesnt provide enough time to dissipate.

So, back to the train vs motorcycle...... lets make it motorcycle vs car.

its not that weight doesnt matter. (you see the problem with the discussion. misquote or misunderstanding is a major issue) Its that weight is LESS of a factor than speed. KE is (1/2mass x velocity squared)

motorcycle 200lbs KE 1,440,000 KE 360,000
car 2000lbs KE 14,000,000 KE 3,600,000
speeds 120 at the brake marker and speeds of 60mph at the turn in.

this shows that the go kart could use 1/10th the brake size if it had the same HP/weight as the car have similar braking issues or temps. (assuming all the other factors were the same)
since we all know that motorcycles have much better HP/weight, say the bike goes 240mph. that KE jumps to 5,700,000. stilll near a little less than 1/2 of the car

There is a certain weight of the car that would equate to the same KE of the motorcycle.

If you had 2000lb 80mph top speed car, you could use the same brakes as the motorcycle. KE would be near the same. hey, we see that all the time with the miatas (kind of reality at laguna for miatas) ..... you get the idea.
If the motorcycle can stop faster, then its braking force/power goes up above the miata, because the brakes have to dissipate the same energy over a shorter period of time.

think of indy cars hitting the tire wall head -on at 120mph. the car is basically vaporized as it slows to 60mph instantly, driver killed as it slows then gently from 60 to 0. Same KE as going from 120 to 60 for cars on track slowing gradually, but done much faster. alll the energy goes up in heat and car deformation.

the permutations and combinations/factors are endless.

but you get the idea. lighter doesnt make it easier on the brake, because you can store, usually proportionally more energy in the vehicle by going lighter.. You go faster, but you didnt solve the heat issue for the brakes. you will usually make it worse, or unchanged.

Mahler9th

As has been said, Laguna is just tough on brakes.

I know the 911 that has been mentioned here as having similar sized rotors, but 911s are different from front-engined cars. I have experience with both at Laguna Seca (power in the mid-to-high-300s, big tires and car weight between 2-3k pounds), and it is not a good comparison.

I do know of many, many front engined Porsche cars that have power and weight and weight distribution similar to Mark's, and have the similar sized rotors and calipers, et cetera (based on what I think Mark has), and no issues. This after being in this area for a couple of decades.

I haven't read everything MK has written, but I am sure that many (probably most) of his physics and math, et cetera, musings are technically incorrect and a big waste of time.

I have seen no specific details of what he is running for calipers, rotors, MC et cetera (that is what the existing system is on the car) nor what has been already done in terms of ducting and/or other modifications from what PAG shipped when the car was a new street car. This make sit tough to offer specific suggestions about components.

I am not sure that there really is a problem to be solved nor an opportunity for system improvement that will create opportunities for MK and his car to be more competitive. If there really is a problem or an opportunity, I'd be happy to help solve it, in person as I live nearby. For free.

We also have readily accessible local pro racing technical resources that are good Porsche friends. But I seriously doubt MK is interested in leveraging these resources.

All of that said, I too wish him luck.

mark kibort

Mike, ive Always put up the numbers and the reasons. the responses i go nuts with , are "you are wrong". Thats it, its me that IS providing proof or logical ideas. Its NOT the clowns that think a bash fest will make themselves feel better about themselves.

Ok I liked your post so, let me respond.

i have a problem at one point, because its the greatest change in KE on the track. I can go easy on the brakes to their thermal limits, but i have guys shoot on by with the bigger brakes and lighter cars. the guys that are the same weight, i can usually hang with . the guys that out brake, have the 15" rotors! like what world challenge or even T1 mustangs have now. so, i dont see it as a technique issue, because my only option is to brake less, not an option. as it is, im over braking and not even near turn in speed, where i then sacrafice the tires and trail brake, early apex into the turn. very effective, but not good on tires and solving part of the braking issue. the same fade with the more aggresive pads, only ended up grooving the rotors during the fade cycle. proof in the pudding, at sears, the brakes were fine, and rotors were cleaned up nice and smooth.

as far as your car goes, i remember one of anderson's 928 competitors at laguna with POC. He had the 993powered (330rwhp) 911 , that weighted about 2200lbs. he could barely keep up with the 928 with the 500rwhp and 2850lb set up. Anderson usually won the races around 1:31. I dont think your 380hp flywheel, 320rwhp, would run this fast at laguna. did it? if so, that would be a testimate to your driving, but more importantly, you are 250lbs heavier than me, and im only borderline on the brakes, in this one area, and with pad much smaller. Ive had NO brake issues at any other track around and the 993TT brakes are big reds ,which have about 50% more pad size to distribute the head on the rotor and pad. Now, i think you are missing the point. if the brakes work with 2750lbs, they will work going faster as you lighten the weigiht. KE will remain the same or go up slightly. As i said, there is a trade off with weight. KE is the generally the same at the braking points as you go lighter. the point is, going lighter doesnt lighten the load. in fact it might actually make things worse and that is the MAIN point. worse because not only is the KE the same, your ability to stop even sooner to a turn in speed, is better. this depends on a lot of things, not limited to set up, tire compound, etc. But, dont believe me. KE is a real factor. its based more on speed than weight, so its something to consider as truth, and you can verify this with anyone that knows the science. Its the reason folks are running 15" rotors, huge ducting and calipers with pads the size of notebooks! the new cup cars get up to 150mph down the main straight of laguna.
thats 44% more KE (2750lbs 150mph) than what Im doing today with only 20% more leverage, thermal mass, surface area.... so the rest, has to come in from cooling, and higher grip materials at the high heat. And that number goes even higher with trying to dump that heat in a shorter period of time!!!

mark kibort

Love to discuss it.
Now as far as my math, physics, etc.... if you find a problem with any of it, let me, and the rest here know. up until now, everyone's answer is basically you need more cooling or rear bias. Im skeptical, but willing to try.
the reasons im having issue, i believe, is due to a max capability of the 12.6" rotor to decelerate to the speed i need to get to , from 130mph. as said before, and you know me and my car. you and i have run wheel to wheel before with a few of your cars, i have had no issues to this point. i think its a energy requirement in the 100feet of the braking zone that is over the capability of the rotor, pad set up.

btw, im using stock MC, and stock size calipers. (basically the F40/F50 ferrari caliper), but no where near the size of the big reds. im also using 965T 322mm rotors with caliper spacers. pedal pressure is a dream for race weekends on top of race weekends with no bleeding, or spongie pedal. fluid is stoptech higher temp stuff and new.

im hoping that there is enough rear wheel brake force that can be taken advantage without upsetting the car in trail brake mode with a bias change, and dont have much confidence in the cooling ducts, due to my test of no brakes for an entire lap, and then hitting turn 2 laguna hard, with the same outcome. so , the cooling solution depends on whether air flow, better than what im using today in the deflective system, will take that enormous amount of heat out of the rotors and pads to cure the fade. I just think its beyond what air can do over such a short period of time. but, doing it anyway.

ir_fuel

mark kibort

KaiB........Actually, it does. You will be missed!
I want to know of the car that runs 1:31s and has the same HP-weight as i do. running 322mm rotors.

Oh, the comment about , "you know where to find me", is to stimulate competition. or to challenge those to see if they would ever say the things they are saying here, in person. (as they usually NEVER do.....I call it internet courage! ) Anyway, nothing like a good grudge match for a race!

mark kibort

Can you contribute something of value????