ir_fuel

What amazes me about this topic is that the topic starter has tried a lot of stuff which doesn't work, yet argues about the propositions others make about what might solve the problem. I don't really see the point of starting this topic if you seem to know the answers already.

Veloce Raptor

Q.E.D.

Nontheless, as may of us have stated, the simple solution is more & better brake cooling.

/thread

kurt M

You are learning quickly. This is a classic Kibort thread and there is a standard formula that is being followed. MK presents a problem or idea that is both simple and well documented in solution. He then presents all kinds of non-relevant data and ideas. Good meaning people post well formulated answers to what are simple problems to most clear thinking track rats. MK faps away splattering the keyboard with fault in every solution or finding presented and the thread veers off into koo koo land. Then it goes all funny as people now understanding that MK will never, ever, agree to anything, regardless of how clear and simple the answer is, start having fun with it.

MK's car is not unique. It is not substantially heavier than many cars, not more powerful than many other cars and yet being MK’s car it has an issue that unique. It simply cannot to be cured in the ways that follows the laws of physics with well documented success by pro teams and amateur racers alike.

Matt Romanowski

I was hoping we could break the mold on this thread, but it doesn't seem to be happening.

I had a friend with a crazy girlfriend. We figured out that when she processed what you said, it went from normal to crazy. So then we started saying crazy things and she processed them to normal. With that idea, I think Mark's brakes are not up to operating temp. He needs to get them hotter!

kurt M

For the rest of us. i took a slightly non standard tack to getting air into the brakes. I went with volume over carefull placement. As I could change the front end as I saw fit i made large intake ducts and added turning vanes to keep the air moving along and then blasting into the rotors and calipers. No little ducts to get knocked loose or pinched. Gobbs of air and the pads and rotors last forever.

as noted it is simple energy gets changed from one form to another. Unless you remove the energy it builds up. In this case it is heat in the brake bits. Remove the heat between cycles or regardless of how large the parts are they will become too hot.

ir_fuel

That's some serious cooling you've got going on there!

Too bad it only works for all corners on all tracks, except one!

Mahler9th

Lol, some folks march to different drummers...

Look... optimized cooling may not be a complete solution, but is a worthy start as has been mentioned over and over. This is racing 101 and dates back decades.

I don't think you need to know the temperatures and all of that other yoga... just get things in proper order first (including better leverage of the rear) and see what's up after that.

Physics, thermodynamics, heat transfer, material science, racing technology and all of that is not unfamiliar to me as an engineer with an advanced degree and a racer with almost 30 years of experience. But none of that is really very productive unless or until the basics are addressed.

I have a really funny picture from RR IV at Laguna which shows and accomplished technician and racer addressing his ducting between sessions because he (like me) was having a long pedal issue at 11. The picture is funny because two friends were sitting in lawn chairs offering free advice and poking fun. This car is like mine and weighs less than 2000 pounds. The four of us have extensive experience with Laguna, but still two of us were just slightly exceeding thermal thresholds. Why? Because we don't get to race there in anger on a regular basis (due to sound restrictions).

Anyway, Laguna presents higher requirements for braking systems in some cars than other local tracks. It will be interesting to see how many folks that haven't accounted for that during this Fall's SCCA runoffs.



In any case, I think MK (whom I have known for what, nearly 20 years?) has more than enough experience and information to get this cleared up and I am sure he will.

Tim Webb

This reminds me of my folks playing golf . Mom had an 8 handicap and Dad's was probably a 6 at the time.

So Mom misses a shot and says," Honey. What did I do wrong?"

Dad replies," Well it looks like you are taking the club way past parallel. Try shortening your back swing."

Mom shoots back," I am not. What do you know."

She storms off.

mark kibort

I think you have missed the entire point of this thread. Its a discussion. i haven't tried anything but a bunch of different pads. I have more time at this track than most, so i thought it might be an interesting discussion. the only proposition brought up is cooling.... im discussing if that really is the answer. its valid discussion and question, right? Oh, and one other thing..... the other main point of bringing all this up was that the "expert" said i had bedded the pads incorrectly, and that was my issue. I wanted some feedback on that too, as i dont think i did anything wrong in my bedding in of the bakes. in fact, i take a lot of pride in the way i do that process.
so, again, nice to all this color to the discussion, but i dont have the answers, hence the questions.. I have a lot of information, so just trying to see what would work. best. once possible answer is cooling. I'm looking at being convinced here, the other as 333 has said, is rotor size. It just feels like the rotors cant handle the task, regardless of cooling. however ive already said, im going to try it out.
Its possible. im not discounting it at all. but when the responses have holes in the theory, im offering to point it out to, again, discuss. the only holes ive seen is that the cooling effect, with ducted air might not be able to keep up with the heat generated in this 2 second area of braking at laguna at the speeds ive seen and weight im carrying. I think my problem is a little unique, because not many have seen 130mph, with 3000lbs with a 12.6" rotor.


Now, lets put your ego and put down tendancies aside for a moment. ive brought up a problem that IS a little unique and brought up some factors that might make ducted cooling unable to solve this problem. I wanted it to be a discussion because of the things that other " experts" have told me. remember, the original problem was how i bed'ded the brakes. I dont think an pro team would think how i bedded them was in anyway, wrong. in fact, i take a lot of pride in understanding how to bed brakes in properly.

Yes, so my situation is a little unique. most of the club racers only hit 120mph down the main straignt, and this goes for many of the high hp cars that are heavier too. at 130, there is a LOT more kinetic energy to dissipate. to get to the turn in speed. I in no way am ignoring that ducted cooling can help the issue, and maybe even solve it. I have doubts based on what i said the problem is. I did disagree if you could lower the rotor temp going into the problem area, because of how fast the temp rises in the area im talking about. the very end of the braking zone, for 1 second, if the temps are too high, and are exceeding the pads ability to create friction, more pressure is applied and even more temp is produced. this is not rocket science here. this all happening at a pretty low speed too . (probably the 80 to 60mph range when the fade occurs)... .... So, if the poster is not correct about the lowering of the starting temp, then , we have to assume that the air flow during the last portion of braking, or the approach speeds , is enough to take all this temp out of the rotor, to keep the temps in a range the pads need to do their job.

isnt there a decent possibility that we have exceeded the temps for the job? 12.6" rotor diameter, might just not be able to do it. the more aggressive pads just had the same fade, but was able to have a different mechanical structure to provide nice deep grooving when the "overpressure " was applied.

Its a discussion, not an argument. those of you that are engineers or think like one, can understand my points. the others, might take offence or see it as argumentative or stubborn, but clearly to me, its not. why, because im looking at all solutions and looking at what has done before to solve it as well.

you find me a viper/vet or pumped up 965T that has run a 1:36 on DOTs with 12.5" rotors, and did it with some duct work, ill be all ears. Ive been doing this a long time. Ive raced with even smaller rotors for many years too, with some issues and techniques to get round the problems, but im trying to figure out if this extra speed at the end of the straight, is just too much for the rotors being used.

Many mention ducting as the solution, but there are (almost all) many teams and club guys i race with, and ive driven those cars, where the brakes are perfect in this area, at near the speeds discussed because the rotors are larger. DE guys, club racers that only hit 110 to 120 down the straight have plenty of capability with 11 to 12" rotors. (my opinion and experience). i think when you take the next step up at laguna with power, the task gets more complicated for the power required to slow the car .
remember, im not having any soft pedal. or any issues at sears or thunderhill at relatively same lap time performance. (maybe thunderhilll at turn 13 )

So, can you keep this to a discussion, rather than lambasting someone looking at all the causes and solutions possible? Ive already said im going to get some ducting work in there. I know how to do it and we can see what the effects are. if it works, great. problem solved. if it doesn't, its time for the larger rotors.

mark kibort

interesting point regarding heat build up between cycles..... i forgot to mention that i tried a test to lower temps before the braking zone of turn 2. I think i posted a time i ran with NO BRAKES at laguna. its a time that would rival the majority of all the club racers that hit laguna . a 1:46. no brakes at all. so, i ran a lap during my issues with no brakes and then hit turn 2 braking zone. no difference. same brake fade ive seen along the way...... this is one of the reasons i have my doubts that cooling can solve the issue, unless during the braking zone, the air flow (some level of CFM pointed at the rotors ) can take away the heat needed to solve the over temp of the pads and rotor issue. I have my doubts, thats all. this test was a valid one. Its not like i dont have any air going to the rotors. proof be seen on the rotors themselves. when i was cracking the holed rotors every 3 weekends (965T rotors), the cracks and near destruction was only on the outside, the inside was smooth and with out spider cracks.
my ducting and deflection gets a lot of air to the inside of the rotor. I dont know if the ducts will do enough to change the problem. like i said, im willing to try anything before going to the 2 piece 14" rotors.

let me post a picture of what i have going on now. also, when i do the ducts. ill take a hole saw and punch a hole right below my foglights that will go directly to the brake area with a 3" duct tube. (if you see my avitar, you can see where the hole will be placed)

mark kibort

928 transmissions are a bear. expensive to fix, but they are usually bullet proof. i caused this issues when installing the transmission after breaking the main shaft after 10 years of racing! the rubber boot forced some pressure on 2nd gear , so it wore the keeper lip down over 2 years. now, its toast! but the sycnhro itself still works, but it falls out of gear. have to replace the entire transmission and i hate holding it in 2nd around turns where you need more control!! going in probably at the end of the season.

Thanks! i was looking for those! ill order some today!

That's the question, right??? when the pads are doing their job, more of the energy is going up in slowing the car than when the pads fail. then, the more you press (and you can create a LOT of pressure by pressing harder), the more energy goes up in heat, and only heat as there is no more decel possible.
so, its not that simple. this is why larger rotors work so much better. power is Force x speed, right? for the same decel rate, i can use less force (15% less force with a larger rotor) but the speed is higher at the larger diameter. so, for less friction, you are getting the same energy , and more of it is going into slowing the car down. 15% reduction in friction is a HUGE reduction in heat. not to mention the greater surface area for it to work on.

actually, lightening the car will make things worse. why, because KE is a squared function to speed, and 1/2's the weight. (1/2MV^2). so if i lighten the car by 200lbs (like adding 20hp for a 10:1 hp/3000lb weight car) i might get 5mph faster down the main straight. now, i have to slow it.
rough calculation = 120 vs 125mph for KE is : 21,600,000 heavy car vs lighter car 21,875,000. you just made the problem worse.... but, you might be able to turn in faster due to the lighter weight, so that would help a little. looks like it might be a wash at best.

venting is something ive done a lot with. ive vented the hood for downforce and the fenders at the sides. almost ready to vent upward as well, but that would be a trade off, if you wanted the air to exit the wheels via the rotor vs being diverted upward to help with downforce.

Ive been talking about coleman rotors for years now. i had someone that would make me the custom hats, but cant get him to commit . however, i know the rotors are not that expensive and that truely is the way to solve this problem. do you know of the best source to make custom hats for the 350mm coleman rotors . I need them to be 965T offset ( C2 turbo )

mark kibort

I nice workmanship. Im trying to understand the chamber before the air exits to get to the turning vanes (not shown yet, right?). that chamber has a flat edge at the rear. its almost made thinking like having the volume of air in the chamber will feed the inlet. Air flow might not flow that way. what might happen, as you have a fixed pressure at the nose of the car, say about .1psi at 100mph, and that flow runs to the lower pressure zone in the wheel well. however that back wall could create a lot of turbulence of the flow. (kind of like having a flat plate in the air stream that would cause more drag) Thats why the tubes work (or making that a straight square tube all the way back to the turning vanes by just walling off the extra chamber area) And then, what does it look like at the turning vane? a big opening pointing to the hub and rotor/caliper?
be cool to see more pics.

winders

Look, this is really simple and I don't know why you make it out to be so complicated. This is not a unique problem and you car is in no way special.

Assuming the issue is not overheated brake fluid or the pad choice, you need to do the following:

1. Verify you are running an appropriate bias ratio. If you are not you need to address this. You want the rear brakes doing their share of the work. This could be the entire problem.

2. If 1 is not the issue, you need to improve the air cooling as much as you reasonably can.

3. It is possible the only way to actually solve the problem is to increase the mass of the rotors. You just may need bigger heat sinks.

Items 1 and 2 are no brainers.

mark kibort

This is why i brought this up for discussion. (there was talk of possible bed in issues of this "very special and most modern pad", the ST41) as well as brake bias issues.

First, help me understand if its brake bias, how that can be an issue. You (and I) will always brake to the limit of the front tires. if you have more rear brake bias which means i will slow a little quicker based on their effects. Sure there is a slight CG lowering, but that is not as much as a factor as slowing down slightly quicker. Yes, im light on the rear brake bias, but how much more can i dial in before i effect a distinct braking style of aggressive trail braking so that the rear inside tire locks up or starts to break free the loaded rear tire? there is only 250lbs on each of the rear tires under a 2g slow down. And, even if it did help, how much more would it slow the car down to lower the duration of front brake applied? now, certainly you could raise brake bias and lessen burden on the fronts for the same slow down rate, but again, we are taking slow down, based on limits of the tires up front and i dont see how the rears could shorten the time the fronts were applied at the tire limit.

2. air flow. again, i will address this, but my thoughts on that were that the problem is in the last 2 seconds of braking. dont know if air flow has the ability to help this immense heat in the pads. also , i mentioned that i experimented with turn 2 by not using the brakes for a fast lap (1:46ish) and then hit turn 2 braking zone. no change. meaning, these brakes started out as very cool.
but, you dont want to be too cool as the pads have an operational range too, and it seemed like they were not. however, i would bet that the air flow i have today, for a lap with no brakes, is cooler than a lap with air flow before turn 1-2 at laguna.

3. Another interesting idea.... But, keep in mind, i have more heat sink on my rotors that most any race car ive seen. stock rotors are near 20lbs and are mounted directly to the hub, so i truely have a huge heat sink, which is a lot more than a 14 or 15" 2 piece rotor, which are thermally isolated to the rotor center, which is bolted to the hub and the actual rotating wheel, which is a HUGE heat sink too!! with a 2 piece rotor, 14 or 15", the mass goes way down, but the leverage point goes up 15 to 20% over a 12.6" rotor. This is the real benefit. Heat sinks and air flow. all interesting discussion. i would willing to bet, my heat sink of the 20lb rotor, 50% more mass than a 2 piece 14" rotor, bolted to the hub and attached to the alloy wheel, would take a huge amount of air flow to match with ducting . however, i think that the heat rise is so quick and so localized that the real question is how to get it out of the pad rotor area during this 2 second of fade at the end of the braking zone. air flow might do it................. or, the forces involved are just too much for the 12.5" / 32mm thick rotor, which would make the logical solution be the 14" rotor.

However, maybe going back to #1, im underestimating the power of the rear brakes. certainly im very very weak on rear bias. i can pretty easily turn that up and experiment as well.
ive done some tests on the jack stands with the rear brakes , ball-parking how much braking pressure it takes to fight against 350ish hp (to get to steady state RPM.) so , they are working, but the question is how much more can i live with to help.
thanks.

Veloce Raptor

Shark...jumped!