Racing Brake Pad / Brake system discussion/questions
07-03-2014, 07:14 PM
#1
Rennlist Member
Thread Starter
Racing Brake Pad / Brake system discussion/questions
After running for over a decade with a car that had brakes that fade down down Laguna’s main straight, I decided to try to see if some of the hype of the new technology in brake pads could help. I thought it was really a factor of the lap times I was running and the hp and weight of the car. (1:36.1 best, 3000lbs 370rwhp) Tires were used Hoosier A6s and sometimes used Pirelli WCGT slicks. The well driven cup cars seemed to drive right by at the end of the braking point, aided by a lighter car, stickier tires, and 14” or larger rotors and bigger calipers. Im running an slightly larger diameter rotors vs stock 12” going to 13”, but I basically thought that was the limiting factor.
After some analysis was done on another discussion, the brake “experts” suggested I got out of the dark ages of running pagid black RS14 pads and step up to much more modern technology , such as the PFC-01 (as was suggested on this discussion board too), and Porterfield S4. Both were improvements, maybe equating the improvement that I felt when going from 12 to 13’ rotors, but nothing earth shattering. I could brake a little deeper, and still have more bite than my old RS14 pads.
One brake Zealot said that I was still in the dark ages, and to try the Raybestos ST-41, but probably to really go to the ST43, because the ST41s were what NASCAR uses and I might not be able to modulate the brakes to avoid lockup…… . Well, I feel I have a pretty good feel for at-limit braking, so I got the ST-41. I bedded them like I always do . on the hyway at night . a few 100 to 60mph cycles until I feel the pedal fading and then I let them cool and do it again. (very minor punishment compared to even a moderate track lap). I smell the resins cooking out of the pads, and that gives me a head start on the race weekend.) sure enough, I still needed a few 80% laps to get them to feel right, and then a cool down lap and then I hit it 95 % for a practice session. They were definitely more grippy. No problem to modulate, just a better bite for less pedal pressure. But, as I approached the final braking zone of turn 2 laguna, the threshold brake still proved too much for the pads as the would fade just before turn in, causing me to continue to use an aggressive trail braking to get around the apex and and stay on line. During the race, I purposely went even deeper than I had tested I could, and sure enough , even a panic pressure couldn’t slow car any more, so again, aggressive turn in (push) to slow the car into the turn before throttling out. In the paddock after, the pads were showing the white look on the pad material, just as the pagids did. But something was different in a big way…. The rotors were grooved pretty badly. In fact, I noticed this from the first 80-90% effort practice session and even worse after 10 laps of qualifying. Post race, they looked pretty bad.
After reporting my experience on the other discussion board, of course, it was my set up of not enough rear brake bias that was the issue. (a purpose detune of the rear bias so I could go aggressively into trail braking and not lock up the inside rear tire or cause some looseness. (even compression braking was causing me some turn in looseness until I disabled the fuel cut off, which reduces the rear braking force, so I figured I didn’t need much rear brake as the car was seemingly standing on its nose anyway and going as deep as other faster cars with more power.
The logic was that with more rear bias, I wouldn’t “overwork” the front pads as much and not groove the rotors. I don’t believe this, but thought I would toss that idea out there for discussion. I feel , If rear bias will help, then all that will change is that ill slow quicker, because im always going to brake the fronts to the limit of the tires, not the pads, so I don’t see how I can be easier on the pads by having more rear bias. If so, let me here the logic, because their logic didn’t make any sense. The only valid idea I could see would be is if im slowing quicker, then im off the brakes earlier and generating less heat into the fronts…. But, that means if I was to get additional HP, that little safety margin was going to be used up. Ive already seen my particular platform run 1:30.9 at laguna with bigger tires, 200more hp, and 14” rotors on pagid black pads, so im still thinking, it’s the rotor size that matters. . That leverage 1” further out gives 15% more torque for the same pedal pressure, even though the rotor vs the pad is going 15% faster. (with more mass to discard the additional heat)
Also, I was bedding them wrong…… said I killed them using (again, using the word archaic ) technique to bed them, that didn’t need to be used with this new generation pad.
Considering the fact that my 80% lap for practice allowed me to smell the resins ,and see the lack of grip when hot, leaves me to believe that they are not much different than other pads. However, the process seemed to be faster , I would give them that.
Im not boiling the fluid, which is the StopTech racing brake fluid. Pedal felt good the entire day, but the rotors are near destroyed. Im thinking that those pads either are just too much for the metallurgy of a stock Porsche rotor, or that the pressure having to use to stop a 3000lb with the speeds generated by 370rwhp, is too much and the rotors get crushed, where as with 14s, I don’t think this is the case. A lot more leverage, using less braking pressure on the rotor to get the same stopping forces. Too much pressure, creates much more heat than friction and then you get fade.
Im welcoming comments , because im at a loss. The fact that the rotors are near destroyed over a weekend is odd, but I do know of some cars that work well on 13” rotors and the pads I use (ST40 stoptech size pads, but Porsche brembo calipers on 13, not 14” stoptech rotors). I also know this problem doesn’t show itself as much at Thunderhill and Sears due to the lower top speeds before turn ins. Particularly interested in folks that have turned up the rear brake bias and the effect that has had on slowing performance. I don’t see it being a game changer, due to the weight transfer of a 1.5 to 2 g stop. We are talking 75-80% of the weight is transferred to the front wheels, leaving only 250lbs per wheel on the rears to help slow the car down. (just a function of wheel base, ride height and stopping rate)
Im off to Sears for an SCCA race weekend this saturday and will use the same brakes one more time as they still work well. Im just concerned by the wear pattern and planning to get larger front rotors custom made some day soon.
Thanks for the help in advance.
Mk
After some analysis was done on another discussion, the brake “experts” suggested I got out of the dark ages of running pagid black RS14 pads and step up to much more modern technology , such as the PFC-01 (as was suggested on this discussion board too), and Porterfield S4. Both were improvements, maybe equating the improvement that I felt when going from 12 to 13’ rotors, but nothing earth shattering. I could brake a little deeper, and still have more bite than my old RS14 pads.
One brake Zealot said that I was still in the dark ages, and to try the Raybestos ST-41, but probably to really go to the ST43, because the ST41s were what NASCAR uses and I might not be able to modulate the brakes to avoid lockup…… . Well, I feel I have a pretty good feel for at-limit braking, so I got the ST-41. I bedded them like I always do . on the hyway at night . a few 100 to 60mph cycles until I feel the pedal fading and then I let them cool and do it again. (very minor punishment compared to even a moderate track lap). I smell the resins cooking out of the pads, and that gives me a head start on the race weekend.) sure enough, I still needed a few 80% laps to get them to feel right, and then a cool down lap and then I hit it 95 % for a practice session. They were definitely more grippy. No problem to modulate, just a better bite for less pedal pressure. But, as I approached the final braking zone of turn 2 laguna, the threshold brake still proved too much for the pads as the would fade just before turn in, causing me to continue to use an aggressive trail braking to get around the apex and and stay on line. During the race, I purposely went even deeper than I had tested I could, and sure enough , even a panic pressure couldn’t slow car any more, so again, aggressive turn in (push) to slow the car into the turn before throttling out. In the paddock after, the pads were showing the white look on the pad material, just as the pagids did. But something was different in a big way…. The rotors were grooved pretty badly. In fact, I noticed this from the first 80-90% effort practice session and even worse after 10 laps of qualifying. Post race, they looked pretty bad.
After reporting my experience on the other discussion board, of course, it was my set up of not enough rear brake bias that was the issue. (a purpose detune of the rear bias so I could go aggressively into trail braking and not lock up the inside rear tire or cause some looseness. (even compression braking was causing me some turn in looseness until I disabled the fuel cut off, which reduces the rear braking force, so I figured I didn’t need much rear brake as the car was seemingly standing on its nose anyway and going as deep as other faster cars with more power.
The logic was that with more rear bias, I wouldn’t “overwork” the front pads as much and not groove the rotors. I don’t believe this, but thought I would toss that idea out there for discussion. I feel , If rear bias will help, then all that will change is that ill slow quicker, because im always going to brake the fronts to the limit of the tires, not the pads, so I don’t see how I can be easier on the pads by having more rear bias. If so, let me here the logic, because their logic didn’t make any sense. The only valid idea I could see would be is if im slowing quicker, then im off the brakes earlier and generating less heat into the fronts…. But, that means if I was to get additional HP, that little safety margin was going to be used up. Ive already seen my particular platform run 1:30.9 at laguna with bigger tires, 200more hp, and 14” rotors on pagid black pads, so im still thinking, it’s the rotor size that matters. . That leverage 1” further out gives 15% more torque for the same pedal pressure, even though the rotor vs the pad is going 15% faster. (with more mass to discard the additional heat)
Also, I was bedding them wrong…… said I killed them using (again, using the word archaic ) technique to bed them, that didn’t need to be used with this new generation pad.
Considering the fact that my 80% lap for practice allowed me to smell the resins ,and see the lack of grip when hot, leaves me to believe that they are not much different than other pads. However, the process seemed to be faster , I would give them that.
Im not boiling the fluid, which is the StopTech racing brake fluid. Pedal felt good the entire day, but the rotors are near destroyed. Im thinking that those pads either are just too much for the metallurgy of a stock Porsche rotor, or that the pressure having to use to stop a 3000lb with the speeds generated by 370rwhp, is too much and the rotors get crushed, where as with 14s, I don’t think this is the case. A lot more leverage, using less braking pressure on the rotor to get the same stopping forces. Too much pressure, creates much more heat than friction and then you get fade.
Im welcoming comments , because im at a loss. The fact that the rotors are near destroyed over a weekend is odd, but I do know of some cars that work well on 13” rotors and the pads I use (ST40 stoptech size pads, but Porsche brembo calipers on 13, not 14” stoptech rotors). I also know this problem doesn’t show itself as much at Thunderhill and Sears due to the lower top speeds before turn ins. Particularly interested in folks that have turned up the rear brake bias and the effect that has had on slowing performance. I don’t see it being a game changer, due to the weight transfer of a 1.5 to 2 g stop. We are talking 75-80% of the weight is transferred to the front wheels, leaving only 250lbs per wheel on the rears to help slow the car down. (just a function of wheel base, ride height and stopping rate)
Im off to Sears for an SCCA race weekend this saturday and will use the same brakes one more time as they still work well. Im just concerned by the wear pattern and planning to get larger front rotors custom made some day soon.
Thanks for the help in advance.
Mk
07-05-2014, 07:44 PM
#2
Race Director
MK
Too many variables in your car? Still running stock rubber brake lines? Still running 1986 brake calipers with original pistons seals? Yes bigger rotors spaced out via grinding stock calipers with the still small pads that are your only option?
You did bed the brakes WRONG...you did NOT put fresh pads and fresh rotors at the same time...your bedding in the ST41 on the OLD rotors by overheating them on purpose...not a great plan. (still got old rubber lines right)....original pistons-seals?
How old is your brake master cylinder? Has is ever been replaced? What about the BOOSTER.....if it has a slight leak and gets weaker with heat...hmm that will act like you describe....it is over 30 years old....have you tested it? What about the one way valve going to it? Is it still working correctly? Is the vac lines still sealed?
Bottom line .....you have too many variables in your rarely raced car.... The advice you got is correct and modern, your platform is dated and needs maintenance ..... I will summarize your arguement...I have one million races...for a million years....but 4 races per year at 40 min per day doesn't add up to much
Too many variables in your car? Still running stock rubber brake lines? Still running 1986 brake calipers with original pistons seals? Yes bigger rotors spaced out via grinding stock calipers with the still small pads that are your only option?
You did bed the brakes WRONG...you did NOT put fresh pads and fresh rotors at the same time...your bedding in the ST41 on the OLD rotors by overheating them on purpose...not a great plan. (still got old rubber lines right)....original pistons-seals?
How old is your brake master cylinder? Has is ever been replaced? What about the BOOSTER.....if it has a slight leak and gets weaker with heat...hmm that will act like you describe....it is over 30 years old....have you tested it? What about the one way valve going to it? Is it still working correctly? Is the vac lines still sealed?
Bottom line .....you have too many variables in your rarely raced car.... The advice you got is correct and modern, your platform is dated and needs maintenance ..... I will summarize your arguement...I have one million races...for a million years....but 4 races per year at 40 min per day doesn't add up to much
07-05-2014, 07:55 PM
#3
Rennlist Member
Mark:
My 15yr old daughter logs more track time/year than you do.
Time to stop being an expert with 100min/year of hobbs time, in a car you barely maintain, using principles your grandfather last adhered to.
Your hour and a half a year of track time, is anecdotal to people that do more than that in half a day per weekend, 10 weekends a year.
I'm not the bad guy here, don't like it, you have my Email address.
My 15yr old daughter logs more track time/year than you do.
Time to stop being an expert with 100min/year of hobbs time, in a car you barely maintain, using principles your grandfather last adhered to.
Your hour and a half a year of track time, is anecdotal to people that do more than that in half a day per weekend, 10 weekends a year.
I'm not the bad guy here, don't like it, you have my Email address.
07-07-2014, 09:08 PM
#4
Rennlist Member
Thread Starter
Mark:
My 15yr old daughter logs more track time/year than you do.
Time to stop being an expert with 100min/year of hobbs time, in a car you barely maintain, using principles your grandfather last adhered to.
Your hour and a half a year of track time, is anecdotal to people that do more than that in half a day per weekend, 10 weekends a year.
I'm not the bad guy here, don't like it, you have my Email address.
My 15yr old daughter logs more track time/year than you do.
Time to stop being an expert with 100min/year of hobbs time, in a car you barely maintain, using principles your grandfather last adhered to.
Your hour and a half a year of track time, is anecdotal to people that do more than that in half a day per weekend, 10 weekends a year.
I'm not the bad guy here, don't like it, you have my Email address.
your theory of what works, based on 1000s of DE guys is borderline amusing. (those 1000s of DE guys, did what you said and they were all more successful)
Im just talking race physics here. I don't buy if you bed them any differently than I did, that any different result will happen. they were bed correctly. the rotors were perfectly true. no grooves , no lips , in spec. I didn't over heat them. based on all Ive read and all those ive talked to , I did a pretty methodical brake in and it helped the bed in process at the track, because they still were not beded totally from the street exercise
they are 12.6 " rotors trying to get a 3000lb car down from 130mph in short order. it was beyond their capability without fade toward the end of the braking zone.
proof be shown by the experience at Sears Point. they felt much better. never had any fade, because the braking demand with rest is so much greater than Laguna seca. sears has a slight tap at t-2, T-4, at the very end of carocell into t-7 and then no brakes again until 11 and speeds only up to 120mph. a whole different set of dynamics.
and guess what, the rotors got smooth again by the pads not being overworked and over compressed to the rotors.
Also, had the ability to chat with a lot of Sears point locals. (McGee motorsports, and a few others that build and support pro teams and found that what I was saying to YOU was probably pretty near dead on.
the pads are great, I like them, but they are too much for a 12.6" rotor to run up to the limit of the front tires in some situations. there should be much more safey room. in otherwords, adding more rear brake bias has NO bearing on this because all that will do, (if in correct) will make the car stop that much quicker. either way, ill be at the limit of the front tires , so that's a load the pads, rotors , fluild and calipers have to handle.. also a good indication here is the fluid never got any softenss, even at laguna. there is enough cooling to keep the fluid from boiling, but just too much demand to allow that much clamping force on the rotorts at lagunas straight.
Think about it. with a 14" or even the 14.7" rotors many of my competitors are using, they have 15% more braking force when needed, or the same force I have with 15% less pressure. that is HUGE. (not to mention more of the thermal capacity)
Now, when your daughter runs a 1:36.1 at laguna, come talk to me.
Your analogy is like saying taxi cab drivers are likely to be top racers. your logic and recollection is almost laughable.
tell you what, your projection is telling me you need to take a few laps with me. ill bolt on the passenger seat and you give me feedback of what I can do better.
Last edited by mark kibort; 07-07-2014 at 09:28 PM.
07-07-2014, 09:25 PM
#5
Rennlist Member
Thread Starter
MK
Too many variables in your car? Still running stock rubber brake lines? Still running 1986 brake calipers with original pistons seals? Yes bigger rotors spaced out via grinding stock calipers with the still small pads that are your only option?
You did bed the brakes WRONG...you did NOT put fresh pads and fresh rotors at the same time...your bedding in the ST41 on the OLD rotors by overheating them on purpose...not a great plan. (still got old rubber lines right)....original pistons-seals?
How old is your brake master cylinder? Has is ever been replaced? What about the BOOSTER.....if it has a slight leak and gets weaker with heat...hmm that will act like you describe....it is over 30 years old....have you tested it? What about the one way valve going to it? Is it still working correctly? Is the vac lines still sealed?
Bottom line .....you have too many variables in your rarely raced car.... The advice you got is correct and modern, your platform is dated and needs maintenance ..... I will summarize your arguement...I have one million races...for a million years....but 4 races per year at 40 min per day doesn't add up to much
Too many variables in your car? Still running stock rubber brake lines? Still running 1986 brake calipers with original pistons seals? Yes bigger rotors spaced out via grinding stock calipers with the still small pads that are your only option?
You did bed the brakes WRONG...you did NOT put fresh pads and fresh rotors at the same time...your bedding in the ST41 on the OLD rotors by overheating them on purpose...not a great plan. (still got old rubber lines right)....original pistons-seals?
How old is your brake master cylinder? Has is ever been replaced? What about the BOOSTER.....if it has a slight leak and gets weaker with heat...hmm that will act like you describe....it is over 30 years old....have you tested it? What about the one way valve going to it? Is it still working correctly? Is the vac lines still sealed?
Bottom line .....you have too many variables in your rarely raced car.... The advice you got is correct and modern, your platform is dated and needs maintenance ..... I will summarize your arguement...I have one million races...for a million years....but 4 races per year at 40 min per day doesn't add up to much
Luke, you are not yet a Jedi!
you haven't done 1% of the things ive done in building and testing the race cars. (sounding like Speedtoys now) Booster and master and calipers and their seals are all solid and are not the issue. the brakes are fantastic. just under rotor. Sears proved that . I actually the ST41s for Sears. great Bite, and they don't fade in the critical areas. (2 of them). rotors came back to life as well, with a very smooth surface after 5 sessions.
So, yes, I have SS lines. seals are not leaking, vacuum booster is fine. and master is working well . I know those symptoms of what you mention and no, what I describe IS not what is happening at all.
I don't just drive around the track to be out there. I work to find the cars limit. its not poorly maintained. its checked and being a sole race show , I do miss some things, but my record for DNFs are in the 1-3 range over 15 years of doing this stuff.
If you did and built things like I did you would still be racing. I followed those that were successful and did what they did. You decided to reinvent the wheel. hey , how did that work for you?
I tried all the brakes that all on the list suggested. I found that all were slightly better than what I was using, but still the fact seems to remain, I have been at the limit of the clamping force of the calipers and the more aggressive pads just grooved them up at laguna. fine as Sears. Others with a ton of experience as well, seem to agree.
07-07-2014, 09:58 PM
#6
Rennlist Member
Thread Starter
here is the grooving at laguna , even after 80% practice laps. and a lot of them by the way. (full 20mins), the rotors were grooved really badly. after qual, even worse. after the race, I was going to junk them. BUT, after a the first session at Sears, putting the brakes to their limit, the rotors cleaned up. after qual. even better and after the race, they looked just "old" because they are getting the little spider cracks now, but the grooves are all but gone.
all material has hits structural and wear limitations.
the thoughts about adding more rear brake bias, as we talked about, can only reduce slowing time slightly, and you will still obiously us the brakes to the slowing limit of the front tires. *a side issue is with rear brakes, it does squat the rear of the car slightly , to the limit that it can, and that lowers the CG, which also determines the forces you can apply to the front and rear brakes. Those pads at laguna were too much for the clamping force for going into turn 2. same fade as the other pads when way deep in the braking zone, but with some deep grooving as a result of the compound. seems like a pretty reasonable theory to me and others in the know , seem to agree as well. just wanted some non ego biased feedback here, since this is a discussion board.
also , keep In mind, when I used the holed rotors, they were cracked and separating at 3 weekends. solids, seem to triple the life expectancy.
here are the pics. very grooved at laguna and looking pretty smooth at Sears. pics don't do the reality justice, as you can feel the difference with your fingers rolling up and down on the surface. huge difference.
GROOVED VS VERY SMOOTH COMPARED TO EACH OF THE OUTINGS. By the way, I was impressed with the pad wear... almost none. makes sense since the pads are made from more wear resitant materials vs the PFC-01, S4, and RS14s.
edit: one more picture added. what the other are using for rotors vs the GTS rotors
all material has hits structural and wear limitations.
the thoughts about adding more rear brake bias, as we talked about, can only reduce slowing time slightly, and you will still obiously us the brakes to the slowing limit of the front tires. *a side issue is with rear brakes, it does squat the rear of the car slightly , to the limit that it can, and that lowers the CG, which also determines the forces you can apply to the front and rear brakes. Those pads at laguna were too much for the clamping force for going into turn 2. same fade as the other pads when way deep in the braking zone, but with some deep grooving as a result of the compound. seems like a pretty reasonable theory to me and others in the know , seem to agree as well. just wanted some non ego biased feedback here, since this is a discussion board.
also , keep In mind, when I used the holed rotors, they were cracked and separating at 3 weekends. solids, seem to triple the life expectancy.
here are the pics. very grooved at laguna and looking pretty smooth at Sears. pics don't do the reality justice, as you can feel the difference with your fingers rolling up and down on the surface. huge difference.
GROOVED VS VERY SMOOTH COMPARED TO EACH OF THE OUTINGS. By the way, I was impressed with the pad wear... almost none. makes sense since the pads are made from more wear resitant materials vs the PFC-01, S4, and RS14s.
edit: one more picture added. what the other are using for rotors vs the GTS rotors
Last edited by mark kibort; 07-07-2014 at 10:15 PM.
07-07-2014, 10:21 PM
#7
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It sounds like you have a simple cooling problem. What temps are the rotors/pads reaching? That will determine the rest.
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07-07-2014, 11:08 PM
#8
Rennlist Member
Yep, I concur with Matt. Looks and sounds like inadequate air flow.
07-08-2014, 12:02 AM
#9
Three Wheelin'
Get some thermal data. I agree with the above that most likely your issue is with thermal capacity. Yes, more mass will help but improving cooling will help as well. Its probably why you're only having problems at certain tracks. The thermal demands on the brake hardware is different. Pads won't do much to change that. Moving the bias rearward will help to balance the thermal load front to rear but if you're already on the edge it will only delay the onset of fade. Brake cooling can then be tailored to the specific track and tuned for the specific braking demands. At a minimum temperature strips should give you a broad picture of what's happening but ultimately thermo couples on the brake pads will give you the real answer.
07-08-2014, 04:55 AM
#10
Rennlist Member
Thread Starter
Get some thermal data. I agree with the above that most likely your issue is with thermal capacity. Yes, more mass will help but improving cooling will help as well. Its probably why you're only having problems at certain tracks. The thermal demands on the brake hardware is different. Pads won't do much to change that. Moving the bias rearward will help to balance the thermal load front to rear but if you're already on the edge it will only delay the onset of fade. Brake cooling can then be tailored to the specific track and tuned for the specific braking demands. At a minimum temperature strips should give you a broad picture of what's happening but ultimately thermo couples on the brake pads will give you the real answer.
I think ideally, I would use these pads at Sears, because they do have more initial bite and more stopping power for less pedal pressure. But I think at laguna where I get into the over temp range at the end of turn 2, the extra pressure, with the aggressive material, just digs into the rotors.
One thing I wanted to do, which I forgot, was to run the temp strips. Ill make sure I get the temps for the next race.....
07-08-2014, 08:25 AM
#11
Rennlist Member
Are you running ducted brake cooling from the front of the car?
07-08-2014, 09:12 AM
#12
Rennlist Member
And more importantly, if you are running ducted cooling (which is dooubtful), are the ducts pointed at the hub area where the inner cooling vanes disperse from, or just as the face of the rotor? big difference? Also, given the weiight of the car and its high power, ideally having ducted air also aimed at the caliper would help.
07-08-2014, 10:54 AM
#13
Three Wheelin'
It seems like the over pressure during fade caused the grooving. (since no other pad over the last 10 years has shown this kind of issue. And this issue happened on a first practice where I was kind to them, and running 85%) lap times In the same range.
I think ideally, I would use these pads at Sears, because they do have more initial bite and more stopping power for less pedal pressure. But I think at laguna where I get into the over temp range at the end of turn 2, the extra pressure, with the aggressive material, just digs into the rotors.
One thing I wanted to do, which I forgot, was to run the temp strips. Ill make sure I get the temps for the next race.....
I think ideally, I would use these pads at Sears, because they do have more initial bite and more stopping power for less pedal pressure. But I think at laguna where I get into the over temp range at the end of turn 2, the extra pressure, with the aggressive material, just digs into the rotors.
One thing I wanted to do, which I forgot, was to run the temp strips. Ill make sure I get the temps for the next race.....
07-08-2014, 04:23 PM
#14
Rennlist Member
Thread Starter
Brake pads are interesting objects and do some strange things. With fade being a function of too much temperature the output (even before fade) is also a function of temperature. Another characteristic is compressibility. With all the materials packed into the brake lining they all have varying characteristics when they get outside their design intent. Its possible the grooving is coming from a change in compressibility with temperature increase. If you prefer the pad for its initial bite and total output my suggestion would be to improve cooling. VR's suggestion of cooling the caliper could be useful and/or feeding air directly in toward the inner vanes of the rotor.
however it all starts out great at laguna into turn 2, but at the end, they're cooked and im not slowing as fast as i know the tires can handle. so i push harder, on already fading brakes (due to over temp, as you say). at the end, im still pushing so hard , which is putting a tremendous force on the pads, which have lost much of their friction, and all the force is going up in heat now, and probably accelerating the heat, but also taking that aggressive pad and not just torching the rotor surface. like a brake rotor lathe.
its at this point, that i can see that if i can reduce friction force by 15% by using a larger diameter rotor, that could solve the problem. again, ive driven the course with 10mph slower top speeds, later braking points and the brakes have survived AND using much smaller diameter rotors. 11.9 and 11" rotors way back in 2000-2001.
again, the cooling over all is enough to keep even superblue from making the pedal soft or spongie.
And more importantly, if you are running ducted cooling (which is dooubtful), are the ducts pointed at the hub area where the inner cooling vanes disperse from, or just as the face of the rotor? big difference? Also, given the weight of the car and its high power, ideally having ducted air also aimed at the caliper would help.
Ill put some temp measuring tape next outing, and see what i see. the actual proof is that the inner side of the rotors are perfect. no cracking at the end of life, and smooth as silk. this is a result of the air hitting the inside side of the rotor, the outside is limited to the cooling vanes doing their job, but the inside will always be better, unless all the air is forced at the hub, which is the best way. I think a hybrid is best, but i get your point.
as i mentioned, its an integrated cooling inlet, and deflector to the inner hub and rotor area. Not ideal i agree.
However, i think the massive temp increase at the end of the straight of laguna, raises the temp so fast, that i dont think even cooling ducts can match the massive energy release. I think its a leverage thing, that a larger diameter rotor can achieve. keep in mind, i have the same fade at the end as i did with pagid black, PfC -01, but not as much initial bite . the difference is that at the end , when, i start to really push the poor pads harder during the fade area, the pads are not as agresive and dont do anything to the rotors as far as wear. this could be a "compressibility " difference as well as a material difference as was mentioned by 2Bwise.
Im certainly amazed to not see the pads wear as fast though. If i use them at the tracks where the brakes are within their capability, its a bargain for how long they last vs their cost vs others.
07-08-2014, 04:58 PM
#15
Rennlist Member
Mark, for reference, the NASCAR guys often run triple ducting like this for road course use...
