Racing Brake Pad / Brake system discussion/questions
07-22-2014 | 04:47 PM
#272
Thread Starter
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Joined: Feb 2003
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From: saratoga, ca
who need the help here are those that cant engage in a human discussion without insults. Lot's of projection going on here. Maybe we all can get a group session going.
I have appreciated the help and the discussion. Again, I'm putting in the ducts (cant hurt) trying the bias bar (will do so cautiously) and will put on the larger rotors and might even put on the XP20 pads.
the discussion turned out to be an argument that losing weight would solve a braking problem. clearly, that isn't a solution based on what has been presented.
07-22-2014 | 05:15 PM
#273
Drifting
Joined: Sep 2006
Posts: 2,638
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From: Winnetka, IL.
[QUOTE=mark kibort;11524501]Other cars have my sized rotors in the same speed and laptime range (but usually much bigger calipers), but still, they are much lighter weight cars.
QUOTE]
Mark,
Not trying to attack you here, but when you make statements like this, after all of the physics rhetoric, could you possibly see how/why others get so frustrated?
QUOTE]
Mark,
Not trying to attack you here, but when you make statements like this, after all of the physics rhetoric, could you possibly see how/why others get so frustrated?
07-22-2014 | 05:24 PM
#274
Three Wheelin'
Joined: Nov 2004
Posts: 1,307
Likes: 10
From: Northville, MI
When can we expect to hear a report back with some data? It'll be an vast improvement over pontificating about everything else by having some concrete results.
07-22-2014 | 05:52 PM
#275
Drifting
Joined: Feb 2013
Posts: 2,943
Likes: 191
From: TX
Again, there you go reading or seeing what you want, to make your point.
yes, this was about someone saying that losing weight could solve the problem.
Let me address your post because you make a few very IMPORTANT oversights: (and tell me if you or any one can contest my answers to them)
1. You missed the entire part about the aero at 90mph being insignificant, because it could be offset by the downhill section of forces. which is a major characteristic for this particular end of straight. For an engineer, I'm surprised you missed that. If im wrong , call me on that. We all know that the aero loss of a race car might be in the 100lbs drag range at 100mph. its not insignificant. but, if you have ever driven down a friggen hill, and see your car accelerate to 80mph in neutral, with no motive forces at alll, you can see that gravity is a force too and it can cancel out aero losses very very easily. My tahoe goes 85mph down the not so steep areas of the grapevine, with the truck in neutral!! This is why i considered the aero factor insignificant, due to the offset of the downhill section.
I said :
"Yes, ive considered (and we have discussed)the aero losses at the higher speed as well, but those, quite frankly would be small, considering the downhill nature of the straight at laguna. both aero and the downhill, might even be a wash, at least at the speeds of 90 to 120mph."
and now you say that i said "insignificant". you correct me a while ago, on using "dominant" as meaning several orders of magnitude greater, yet, you can take my word "small" and translate that to "insignificant"??? did you even read this paragraph????? if you didnt, i did in the paragraph show why the aero factor would be small. its a trade off with the downhill section forces due to gravity. but you must have missed that.
2. My perceived notion is that i have an overheat problem at the end of the straight based on my weight and speed at entrance. I'm not looking for the math to support my notion. Im looking at a known problem and trying to figure out why! we have talked about bias to the rear brakes to shorten stopping distance and allow release of brakes before overheat. It's not a problem with boiling brake fluid, as pedal is fine, and it happens no where else on the track or other tracks with lower terminal speeds. When someone mentioned weight, we went into KE comparisons, which showed a paltry 5mph (4%) increase for dropping weight (7%) which actually INCREASED KE which would worsened the problem. (the expert, VRs friend at stoptech, already published the article saying that velocity is a more important factor, because its squared in KE.) I was not looking for information that could fit the outcome, i used basic and empirical data to show that losing weight was not a viable solution.
use 3- 4 mph and the outcome is still very weak as far as a solution because of the squared term in KE.
3. It's amazing how in other arguments, others here (folks that you say destroyed my argument) supported such fantasy physics and blasted me for calling them on it. (the 4lb wheel savings helping a 10MPH greater straight line speed at Cal Speedway. VR was on the support team here. But now, when Im saying that 200lbs saivings would add 5mph to a straight, and it's far fetched? 200lbs weight loss effect is several orders of magnitude greater than that argument, and no one was calling them crazy. Bottom line. the simulators are very good these days. 200lbs weight loss on a 3000lb/375hp car, gaining 5mph is not too far off.
Others have compared their cars in this argument at 16% higher speed which requires by the way, a cubed factor to get there! They havent considered aero in their comparisons, but those comments have gone unnoticed. (aero drag for 16% faster speed is 35% more drag and 56% more hp to be able to drive it!!)
In engineering, its important to keep the playing field level. some of the comparisons are all over the map, which makes it hard to follow this discussion.
Did you consider the exit speed at turn 11 before this straight as having more cornering forces and thus more exit speed??? no one mentioned that.
4. as far as the driving part goes. there are several ways to go through turn 11, but im just trying to keep up with my competitors in near like cars.... some of which are actually heavier, and i cant. if i give up more straight line braking (and this is very fundamental and simple here as far as technique) i lose a lot of time, and will certainly lose positions. If i just get the brakes to work at the limit of the tires for the 4 seconds I'm applying them. (very short time), i have solved the problem. this is why cooling doesnt seem like it will work, due to the problem being consistant whether brakes are cool to start or in the middle or end of a all out race. bias might work, certainly couldnt hurt unless it hurt the car in the end of trail braking turns by now locking up the rears and making it unstable. also worth a try.
I think it all points to a larger rotor or the pads that can handle the heat for those 2 last seconds of the braking zone where im getting enormous fade.
5. So, what is the point of your 3919 (velocity^2) , which was 2.3M joule KE based on 140mph and 2500lbs? you know that the decel forces due to drag are now 35% higher now, right? If we had 100lbs of drag at 100mph, we now have 144lbs of drag at my speeds at 120mph, and 196lbs of drag at your 140mph.
My KE for the 120mph 3000lbs car is 1.9M joule. so what is the point? your 2500lb car at 500lbs lighter weight going 16% faster, has 21% more KE.
you already have admitted that a 10% weight loss would require a 5% speed increase to "break even" and have the same KE. my 7% weight loss for 4% is not too far off that, and certainly worthy of a discussion.
Why is your estimation, destroying mine, when our sources of information are the same, and we are both using empirical evidence to make our case?
mine also has a simulator to back it up. go ahead, find a simulator of YOUR choice and let me know if you can corral the velocity gains to less than 2-3% for a 7% weight loss. If so, you would have made your point. AND, by the way, even if you can prove this, it doesn't destroy anything. the KE is still very close (close meaning, less than 2-3% difference) and wouldn't help the problem.
6. ah yes... global warming. now, im not a big Gore fan, but global warming seems real... and it can be almost directly tied to man's industrial age of creating CO2 gases by burning fuels. However, I've seen a ton of evidence that methane is creating even more of the problem, and burning natural gas is a result. AND Methane has a much more direct and easier solution, yet it is going un-addressed. The statistics are pretty compelling, and looking at fossil records, time machine type evidence in the ice of the polar regions, that since man has been burning things, we have seen noted rises in temps well beyond what nature has seen in the earth's history and well beyond what volcanoes and cow manure can produce. Now, I'm not knowledgeable here and had a very strong opinion that it was just the way of the earth, but ive seen some stats that are pretty compelling, recently.
yes, this was about someone saying that losing weight could solve the problem.
Let me address your post because you make a few very IMPORTANT oversights: (and tell me if you or any one can contest my answers to them)
1. You missed the entire part about the aero at 90mph being insignificant, because it could be offset by the downhill section of forces. which is a major characteristic for this particular end of straight. For an engineer, I'm surprised you missed that. If im wrong , call me on that. We all know that the aero loss of a race car might be in the 100lbs drag range at 100mph. its not insignificant. but, if you have ever driven down a friggen hill, and see your car accelerate to 80mph in neutral, with no motive forces at alll, you can see that gravity is a force too and it can cancel out aero losses very very easily. My tahoe goes 85mph down the not so steep areas of the grapevine, with the truck in neutral!! This is why i considered the aero factor insignificant, due to the offset of the downhill section.
I said :
"Yes, ive considered (and we have discussed)the aero losses at the higher speed as well, but those, quite frankly would be small, considering the downhill nature of the straight at laguna. both aero and the downhill, might even be a wash, at least at the speeds of 90 to 120mph."
and now you say that i said "insignificant". you correct me a while ago, on using "dominant" as meaning several orders of magnitude greater, yet, you can take my word "small" and translate that to "insignificant"??? did you even read this paragraph????? if you didnt, i did in the paragraph show why the aero factor would be small. its a trade off with the downhill section forces due to gravity. but you must have missed that.
2. My perceived notion is that i have an overheat problem at the end of the straight based on my weight and speed at entrance. I'm not looking for the math to support my notion. Im looking at a known problem and trying to figure out why! we have talked about bias to the rear brakes to shorten stopping distance and allow release of brakes before overheat. It's not a problem with boiling brake fluid, as pedal is fine, and it happens no where else on the track or other tracks with lower terminal speeds. When someone mentioned weight, we went into KE comparisons, which showed a paltry 5mph (4%) increase for dropping weight (7%) which actually INCREASED KE which would worsened the problem. (the expert, VRs friend at stoptech, already published the article saying that velocity is a more important factor, because its squared in KE.) I was not looking for information that could fit the outcome, i used basic and empirical data to show that losing weight was not a viable solution.
use 3- 4 mph and the outcome is still very weak as far as a solution because of the squared term in KE.
3. It's amazing how in other arguments, others here (folks that you say destroyed my argument) supported such fantasy physics and blasted me for calling them on it. (the 4lb wheel savings helping a 10MPH greater straight line speed at Cal Speedway. VR was on the support team here. But now, when Im saying that 200lbs saivings would add 5mph to a straight, and it's far fetched? 200lbs weight loss effect is several orders of magnitude greater than that argument, and no one was calling them crazy. Bottom line. the simulators are very good these days. 200lbs weight loss on a 3000lb/375hp car, gaining 5mph is not too far off.
Others have compared their cars in this argument at 16% higher speed which requires by the way, a cubed factor to get there! They havent considered aero in their comparisons, but those comments have gone unnoticed. (aero drag for 16% faster speed is 35% more drag and 56% more hp to be able to drive it!!)
In engineering, its important to keep the playing field level. some of the comparisons are all over the map, which makes it hard to follow this discussion.
Did you consider the exit speed at turn 11 before this straight as having more cornering forces and thus more exit speed??? no one mentioned that.
4. as far as the driving part goes. there are several ways to go through turn 11, but im just trying to keep up with my competitors in near like cars.... some of which are actually heavier, and i cant. if i give up more straight line braking (and this is very fundamental and simple here as far as technique) i lose a lot of time, and will certainly lose positions. If i just get the brakes to work at the limit of the tires for the 4 seconds I'm applying them. (very short time), i have solved the problem. this is why cooling doesnt seem like it will work, due to the problem being consistant whether brakes are cool to start or in the middle or end of a all out race. bias might work, certainly couldnt hurt unless it hurt the car in the end of trail braking turns by now locking up the rears and making it unstable. also worth a try.
I think it all points to a larger rotor or the pads that can handle the heat for those 2 last seconds of the braking zone where im getting enormous fade.
5. So, what is the point of your 3919 (velocity^2) , which was 2.3M joule KE based on 140mph and 2500lbs? you know that the decel forces due to drag are now 35% higher now, right? If we had 100lbs of drag at 100mph, we now have 144lbs of drag at my speeds at 120mph, and 196lbs of drag at your 140mph.
My KE for the 120mph 3000lbs car is 1.9M joule. so what is the point? your 2500lb car at 500lbs lighter weight going 16% faster, has 21% more KE.
you already have admitted that a 10% weight loss would require a 5% speed increase to "break even" and have the same KE. my 7% weight loss for 4% is not too far off that, and certainly worthy of a discussion.
Why is your estimation, destroying mine, when our sources of information are the same, and we are both using empirical evidence to make our case?
mine also has a simulator to back it up. go ahead, find a simulator of YOUR choice and let me know if you can corral the velocity gains to less than 2-3% for a 7% weight loss. If so, you would have made your point. AND, by the way, even if you can prove this, it doesn't destroy anything. the KE is still very close (close meaning, less than 2-3% difference) and wouldn't help the problem.
6. ah yes... global warming. now, im not a big Gore fan, but global warming seems real... and it can be almost directly tied to man's industrial age of creating CO2 gases by burning fuels. However, I've seen a ton of evidence that methane is creating even more of the problem, and burning natural gas is a result. AND Methane has a much more direct and easier solution, yet it is going un-addressed. The statistics are pretty compelling, and looking at fossil records, time machine type evidence in the ice of the polar regions, that since man has been burning things, we have seen noted rises in temps well beyond what nature has seen in the earth's history and well beyond what volcanoes and cow manure can produce. Now, I'm not knowledgeable here and had a very strong opinion that it was just the way of the earth, but ive seen some stats that are pretty compelling, recently.
And I thought I was brevity challenged! Is this a filibuster?
Btw hills don't really change squat either - lighter is still better.
-Mike
07-22-2014 | 07:18 PM
#276
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Joined: Feb 2003
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From: saratoga, ca
[QUOTE=mklaskin;11524606]
Other cars have my sized rotors in the same speed and laptime range (but usually much bigger calipers), but still, they are much lighter weight cars.
QUOTE]
Mark,
Not trying to attack you here, but when you make statements like this, after all of the physics rhetoric, could you possibly see how/why others get so frustrated?
QUOTE]
Mark,
Not trying to attack you here, but when you make statements like this, after all of the physics rhetoric, could you possibly see how/why others get so frustrated?
(we are not talking F1 and 200mph speeds and drag levels here by the way)so, you said it yourself. If the speed is 5% greater vs the 10% weight loss, then its a wash. KE is not changing. (speed range is in the 120mph range , so please, no silly 140mph examples or cars with less absolute HP that cant fight the drag as well) So, you agree that if speed is 5% greater, than this is, in no way, a solution for an overheating braking problem? Now, if so.... and i think you agree. the only debate here is how much velocity we gain for a given weight loss. AND, whats the cornering velocity difference for the lighter car. But , you seemed to be missing those key points.
so, Ill get some telemetry, bolt in a passenger seat, and take a passenger down a given straight and then do the same straight without the passenger and see what i get.
In summary of your "destroying my theory"......
1. you discounted aero drag being offset by the downhill section of the main straight.
2. you admitted that 10% weight loss with 5% increase in speed would be a wash for KE .(meaning that this weight loss would have no effect on braking heat dissipation. or in other words, you would still have a heat problem if you had one before
3. you forgot to incorporate faster exit speeds, if in fact a lighter car can corner with more lateral acceleration g's, which it can.
4. because of my test, you agree that cooling might not be the answer, due to the 4 second brake application and there being issues in the last two seconds only . (my test was to run a fast lap, but no brakes applied anywhere, as to see if the fade problem went away. it didnt.
5. you never came up with some approximation of increased rear brake force capability based on a 1.5 to 2g deceleration capability by changing bias in the rear.
6. the only debate here is if a 10% decrease of weight , can provide a 5% increase in straight line speed. Its not that much of a stretch to say that it might. ( my analysis was that a 7% decrease in weight, or 200lbs could allow for 125mph speeds vs 120 before the weight saving.)
It doesn't seem like we are that far off when you actually read what i have posted. (in regards to the lose weight to fix the problem part of the discussion)
the rest is left to be seen. tests will happen. I have temp sensor paint up to 1300 degrees, new duct work and possibly new rotors . I might even bite the bullet and try the higher temp capability pads too.
07-22-2014 | 07:45 PM
#277
Racer
Joined: Feb 2008
Posts: 311
Likes: 25
From: San Deigo
07-23-2014 | 04:49 AM
#282
Thread Starter
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Joined: Feb 2003
Posts: 29,817
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From: saratoga, ca
Greg, suffering from a little projection I see.
yes, there will be a part two, with all sorts of data. telemetry, photos of temperature paint, and results of the bias bar and cooling ducts. so, stay tuned.
predictable
Actualy, this is funny
is that tempurature paint???
You guys are so predictable. You cant help yourselves! Funny..... you guys are like my kids.... so easily amused. its actually cute!
yes, there will be a part two, with all sorts of data. telemetry, photos of temperature paint, and results of the bias bar and cooling ducts. so, stay tuned.
predictable
is that tempurature paint???
You guys are so predictable. You cant help yourselves! Funny..... you guys are like my kids.... so easily amused. its actually cute!
07-23-2014 | 11:15 AM
#283
Mr. Excitement
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From: Fallschurch Va
07-24-2014 | 04:46 AM
#285
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Joined: Feb 2003
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From: saratoga, ca
Anyone that has to resort to character assassination, insults and name calling to win or influence an argument, has no class. PERIOD.
Ask yourself this question..... Why do you post? to help, to fight or win an argument, prove or promote your intelligence? whatever it is that motivates you, i would think that your value and image would be much higher, if you just communicated like you would at a bar or in the paddock with others here.. If you want to discuss, do it . if you want to be funny, crack a joke. But do it with some class. Try and take the high road.
I started this discussion to find a problem that I have at one particular braking zone at one particular track. It started with the 10mph gained by a 15% HP increase getting my car to 130mph down the main straight of laguna. with no other issues anywhere on the track, and no soft pedal ever, I have fade in the last 2 seconds of a 4 second braking zone from 130mph to 60mph..... Ive also done a cool down lap before i hit the straight and braking zone, with no change in outcome. Its a serious fade, that allows me to use tremendous foot pressure on the pedal, with no ability to slow the car down as it should, (to the limit of the tire). once there is even a momentary release, braking force is restored. ( but this isnt an option to get expected braking performance).
Im going to add cooling. (currently, just deflective air plates and routing.) I dont think that will work based on my tests, but am trying anyway. it doesnt seem that there would enough air flow to take the amount of heat out of the rotor and pad in such a short time to help, even if it was flowing better in the 2 seconds prior to the fade problem (fade only occurs in the last 2 out of 4 threshold braking time)
Rear Bias increase has been brought up, and will double rear brake forces, but again, dont think there is enough force to slow the car to point where this would eliminate the problem. if you think about it, i have 2 seconds out of 4 where the KE (heat) is just to high for the pads and rotor to deal with. I dont think bias can take that much distance out of the decel, to make an impact. but will try as well. also, many here are 911 guys with a rear weight balance, that allows for a lot more rear bias. its all about weight transfer. if you get an 80% weight transfer on a 3000lb car, one with 56/44% weight front to rear, vs a 911 with 40/60% front to rear, this is a huge reduction (comparitively) of force being able to be put on the front braking system. (all other things being equal)
Someone suggested lightening the car, but that is fundamentally not a way to achieve any heat or energy relief on the braking system, due to the equation we have been through in this discussion. Its already been agreed that 10% weight reduction to a 3000lb car would increase speed in cornering exit as well as down the main straight, AND if that increase was 5.3% greater than prior speed, the SAME KE would exist. (in other words, there would be no gain in braking heat dissipation)
-- as a side note, the simulators point to a 4% increase in speed is possible for a 7% decrease in mass. aero is included in this simulator. By the way, the laguna seca front straight has a downhill portion at the end that would probably counteract any aero decel forces. Other forces not considered, are engine compression forces and rolling friction on decel. you disagree... show your work as Mike did.
So, I have tried to discuss the topic, but the ignorant or arrogant (or impatient causing an inability to be able to read entire paragraphs before forming retorts) , proved to be too much for the discussion, because god help us if someone does have a unique situation, or a different way of looking at a variation of a popular problem.
In the end, i have some good information by those that did take the high road. I have a test plan the next time out and will report with the data of rotor temps, in the hot pits, after cool laps, after hot laps, and see we can see what can solve the issue.
BY THE WAY I had thoughts: Related to discussion about rear brake bias:
3000lb car 56/44% front to rear vs 40/60% 911 braking comparison.
50/50 during a 2g slow down, there is near an 80% weight transfer.
1500 F to 1500 R goes to 2400lbs front 600lbs rear
Front engine'd 928: 56/44% (1680/1320lbs) under braking goes to 2580 front to 420lbs rear
911: 40/60%( 1200/1800lbs) under braking goes to 2100lbs front, 900lbs rear.
Check my work here, as I dont have the equations handy to calculate, but it seems like if this is true, the front engined car has 23% more weight up front and the 911 has 114% more weight in the rear under decel. (over 2 times the weight!) or another way of looking at it, is the 911 has 19% less weight up front, and the front engine'd car has 54% less weight in the rear. If this is correct, its no wonder you want a lot less bias in the rear on a front engine'd car (for the same at limit braking force) and its no wonder that the rear engine'd car is MUCH easier on brakes up front, given the same braking system size and capabilities.
Ask yourself this question..... Why do you post? to help, to fight or win an argument, prove or promote your intelligence? whatever it is that motivates you, i would think that your value and image would be much higher, if you just communicated like you would at a bar or in the paddock with others here.. If you want to discuss, do it . if you want to be funny, crack a joke. But do it with some class. Try and take the high road.
I started this discussion to find a problem that I have at one particular braking zone at one particular track. It started with the 10mph gained by a 15% HP increase getting my car to 130mph down the main straight of laguna. with no other issues anywhere on the track, and no soft pedal ever, I have fade in the last 2 seconds of a 4 second braking zone from 130mph to 60mph..... Ive also done a cool down lap before i hit the straight and braking zone, with no change in outcome. Its a serious fade, that allows me to use tremendous foot pressure on the pedal, with no ability to slow the car down as it should, (to the limit of the tire). once there is even a momentary release, braking force is restored. ( but this isnt an option to get expected braking performance).
Im going to add cooling. (currently, just deflective air plates and routing.) I dont think that will work based on my tests, but am trying anyway. it doesnt seem that there would enough air flow to take the amount of heat out of the rotor and pad in such a short time to help, even if it was flowing better in the 2 seconds prior to the fade problem (fade only occurs in the last 2 out of 4 threshold braking time)
Rear Bias increase has been brought up, and will double rear brake forces, but again, dont think there is enough force to slow the car to point where this would eliminate the problem. if you think about it, i have 2 seconds out of 4 where the KE (heat) is just to high for the pads and rotor to deal with. I dont think bias can take that much distance out of the decel, to make an impact. but will try as well. also, many here are 911 guys with a rear weight balance, that allows for a lot more rear bias. its all about weight transfer. if you get an 80% weight transfer on a 3000lb car, one with 56/44% weight front to rear, vs a 911 with 40/60% front to rear, this is a huge reduction (comparitively) of force being able to be put on the front braking system. (all other things being equal)
Someone suggested lightening the car, but that is fundamentally not a way to achieve any heat or energy relief on the braking system, due to the equation we have been through in this discussion. Its already been agreed that 10% weight reduction to a 3000lb car would increase speed in cornering exit as well as down the main straight, AND if that increase was 5.3% greater than prior speed, the SAME KE would exist. (in other words, there would be no gain in braking heat dissipation)
-- as a side note, the simulators point to a 4% increase in speed is possible for a 7% decrease in mass. aero is included in this simulator. By the way, the laguna seca front straight has a downhill portion at the end that would probably counteract any aero decel forces. Other forces not considered, are engine compression forces and rolling friction on decel. you disagree... show your work as Mike did.
So, I have tried to discuss the topic, but the ignorant or arrogant (or impatient causing an inability to be able to read entire paragraphs before forming retorts) , proved to be too much for the discussion, because god help us if someone does have a unique situation, or a different way of looking at a variation of a popular problem.
In the end, i have some good information by those that did take the high road. I have a test plan the next time out and will report with the data of rotor temps, in the hot pits, after cool laps, after hot laps, and see we can see what can solve the issue.
BY THE WAY I had thoughts: Related to discussion about rear brake bias:
3000lb car 56/44% front to rear vs 40/60% 911 braking comparison.
50/50 during a 2g slow down, there is near an 80% weight transfer.
1500 F to 1500 R goes to 2400lbs front 600lbs rear
Front engine'd 928: 56/44% (1680/1320lbs) under braking goes to 2580 front to 420lbs rear
911: 40/60%( 1200/1800lbs) under braking goes to 2100lbs front, 900lbs rear.
Check my work here, as I dont have the equations handy to calculate, but it seems like if this is true, the front engined car has 23% more weight up front and the 911 has 114% more weight in the rear under decel. (over 2 times the weight!) or another way of looking at it, is the 911 has 19% less weight up front, and the front engine'd car has 54% less weight in the rear. If this is correct, its no wonder you want a lot less bias in the rear on a front engine'd car (for the same at limit braking force) and its no wonder that the rear engine'd car is MUCH easier on brakes up front, given the same braking system size and capabilities.