brake bias fitting change on 87
08-13-2014, 06:53 PM
#46
Rennlist Member
agree, going to the largrer diameter rotor in front, with no bias change will lengthen stopping distances, because less pedal pressure will use less of the rear brakes. But, the main reason i went to a larger diameter rotor, was to get more bite when the brakes start to fade, which requires more pedal pressure
No, it's because you think 'big' is the solution to screwing up your F/R brake balance by pooching the advice given you on brake pad upgrades, then naysaying the whole planet about it.
08-13-2014, 07:15 PM
#48
Rennlist Member
Thread Starter
When the pedal goes thump against the firewall and continues to when you pump it, there are NO BRAKES. Not fade, no brakes.
And yes i did know the limit of my car to begin with. At that time me in my 944 Turbo was the car to beat. In fact, at the local autocross the ONLY car to get within 4 seconds of my 60 second lap times was ME in my 90 GT.
I've learned that despite the rule of thumb of sliding is slower i.e., drift more than 10-15 degree slip angle, that there are some circumstances and situations where putting the car out of control and catching it, while dangerous and very risky, is faster.
And yes i did know the limit of my car to begin with. At that time me in my 944 Turbo was the car to beat. In fact, at the local autocross the ONLY car to get within 4 seconds of my 60 second lap times was ME in my 90 GT.
I've learned that despite the rule of thumb of sliding is slower i.e., drift more than 10-15 degree slip angle, that there are some circumstances and situations where putting the car out of control and catching it, while dangerous and very risky, is faster.
08-13-2014, 07:17 PM
#49
Rennlist Member
Thread Starter
Tell me that is just a cheap jab because you are too silly to figure out that was a joke. really, alumiunum vs steel pop rivits to hold my rotors together??? your really digging deep now, arent you.
08-13-2014, 07:20 PM
#50
Rennlist Member
Thread Starter
When the pedal goes thump against the firewall and continues to when you pump it, there are NO BRAKES. Not fade, no brakes.
And yes i did know the limit of my car to begin with. At that time me in my 944 Turbo was the car to beat. In fact, at the local autocross the ONLY car to get within 4 seconds of my 60 second lap times was ME in my 90 GT.
I've learned that despite the rule of thumb of sliding is slower i.e., drift more than 10-15 degree slip angle, that there are some circumstances and situations where putting the car out of control and catching it, while dangerous and very risky, is faster.
And yes i did know the limit of my car to begin with. At that time me in my 944 Turbo was the car to beat. In fact, at the local autocross the ONLY car to get within 4 seconds of my 60 second lap times was ME in my 90 GT.
I've learned that despite the rule of thumb of sliding is slower i.e., drift more than 10-15 degree slip angle, that there are some circumstances and situations where putting the car out of control and catching it, while dangerous and very risky, is faster.
08-13-2014, 07:36 PM
#51
Rennlist Member
Thread Starter
Its not that complicated. I'm at the limit down to turn 2. have no issue with any other turn. i get into fade, and its overtemp of the pad in that section due to KE dissipation. sure, im at the limit, and even if i disrupted my Bias with larger front rotor. (common, we are talking .25" largrer diamter), it would only be a few percent. plus the bias via the graph, keeps that pressure pretty constant, after a moderate braking pressure. (in otherwords, regardless of moderate to max front brake pressure -= near the same rear brake pressure).
i would say, nothing is messed up. I've had this fade since i got the KE up from the 130mph at the braking point. I do a lot with a 13 rotor, that so far, no one has come up with a success story. bias could help, but don't see by how much, due to the force created by the existing bias level, especially, since , after a downshift to 3rd gear. the engine braking alone might nearly max out the rear tires. (this is 200ft-lbs x 3rd gear 5:1= 1000ft-lbs, with 24" tire, thats 1000lbs of force on the tire, with only 600lbs of weight on the tires!! Dont know how much more the bias would help, but im willing to try. trail braking, i can get the tail to step out, with the 2nd gear thats near 6:1, or 1200lbs of decel force from 80mph to 60mph on the decel.
Let me take you for a DE ride at sears and ill show you what im talking about. you can ask to see any technique or braking point you want. I can even pull the ebrake if you want on a straight line decel to make the point!
08-13-2014, 07:42 PM
#52
Rennlist Member
Thread Starter
Its not that complicated. I'm at the limit down to turn 2. have no issue with any other turn. i get into fade, and its overtemp of the pad in that section due to KE dissipation. sure, im at the limit, and even if i disrupted my Bias with larger front rotor. (common, we are talking .25" largrer diameter), it would only be a few percent. plus the bias via the graph, keeps that pressure pretty constant, after a moderate braking pressure. (in otherwords, regardless of moderate to max front brake pressure -= near the same rear brake pressure).
i would say, nothing is messed up. I've had this fade since i got the KE up from the 130mph at the braking point. I do a lot with a 13 rotor, that so far, no one has come up with a success story. bias could help, but don't see by how much, due to the force created by the existing bias level, especially, since , after a downshift to 3rd gear. the engine braking alone might nearly max out the rear tires. (this is 200ft-lbs x 3rd gear 5:1= 1000ft-lbs, with 24" tire, thats 1000lbs of force on the tire, with only 600lbs of weight on the tires!! Dont know how much more the bias would help, but im willing to try. trail braking, i can get the tail to step out, with the 2nd gear thats near 6:1, or 1200lbs of decel force from 80mph to 60mph on the decel.
Let me take you for a DE ride at sears and ill show you what im talking about. you can ask to see any technique or braking point you want. I can even pull the ebrake if you want on a straight line decel to make the point!
08-13-2014, 07:59 PM
#53
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they are not locking up.... i mispoke.
EDIT... i didnt mispeak.. i re-read it.... it skates off into the turn... not lock up, but the braking force is so much less, its like you hit ice or are locked up, but we are not locked up. in otherwords, ABS is good for rain and snow, not on the track when talking about 928 ABS. I can prove this at any time, very easily.
20 years of racing here Greg, more experience in a 928 racing than anyone here now. I think i know the car pretty well by now.
what are you talking about. i engage ABS and its way sllower than theshold braking. what can i say. do you think ABS should work better? again, i drive many other cars and do this test the 20 year old ABS doesnt work near as good as threshold braking.. in fact, if i race you and you use it on a 928, ill fly by so fast it will make your head spin.
EDIT... i didnt mispeak.. i re-read it.... it skates off into the turn... not lock up, but the braking force is so much less, its like you hit ice or are locked up, but we are not locked up. in otherwords, ABS is good for rain and snow, not on the track when talking about 928 ABS. I can prove this at any time, very easily.
20 years of racing here Greg, more experience in a 928 racing than anyone here now. I think i know the car pretty well by now.
what are you talking about. i engage ABS and its way sllower than theshold braking. what can i say. do you think ABS should work better? again, i drive many other cars and do this test the 20 year old ABS doesnt work near as good as threshold braking.. in fact, if i race you and you use it on a 928, ill fly by so fast it will make your head spin.
I can simply tell you what I know. You can either listen and take away some of that, or totally ignore my experiences.....either way has absolutely zero impact on my life.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
08-13-2014, 08:46 PM
#54
Rennlist Member
The stop sign corner I described with no brakes was called the stop sign because it was not only the tightest slowest corner on the track it was at the end of the fastest straight. Hence the name Stop Sign, which I thought I described.
AND besides a turn tighter than the turning radius of the car, a tight chicane is another place where doing an out of control tank slapper is faster than a car "hooked up." And have an example to back that one up too. Had a course where I set fastest lap by .006 seconds against a full race prepared 914-6 that was used to setting FTD and I should not have been able to better. I was in my BMW X3 SUV. He watched my laps intently and had his pit crew timing both of us and told me I was beating him in the chicane he was quicker everywhere else on the course. I was treating the chicane like there was something in the road I was avoiding at the last minute before the chicane and throwing the car into a skid. I would then power through the tank slapping recovery from the skid. Timed right the tank slapping recovery is what carried me through the chicane without having to brake for it.
AND besides a turn tighter than the turning radius of the car, a tight chicane is another place where doing an out of control tank slapper is faster than a car "hooked up." And have an example to back that one up too. Had a course where I set fastest lap by .006 seconds against a full race prepared 914-6 that was used to setting FTD and I should not have been able to better. I was in my BMW X3 SUV. He watched my laps intently and had his pit crew timing both of us and told me I was beating him in the chicane he was quicker everywhere else on the course. I was treating the chicane like there was something in the road I was avoiding at the last minute before the chicane and throwing the car into a skid. I would then power through the tank slapping recovery from the skid. Timed right the tank slapping recovery is what carried me through the chicane without having to brake for it.
Last edited by RKD in OKC; 08-13-2014 at 09:11 PM.
08-13-2014, 10:00 PM
#55
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At the First OCIC in Wichita KS they did a DE track day at the track in Hallett OK. I was planning to take the 90GT I had just purchased from Jarrod Wise when the local 944 tuner shop offered to pay me and my expenses for the day if I took my white 88 944 Turbo S. They bought some dyno time for some intercooler testing using my 944 Turbo on the mobile Dynojet that was available for the event.
My personal goal for the track that day in the 944 Turbo was practicing my late braking/trail braking on corner entry. However, I had put on new pads the day before and not taken the time to bed them in before the first session. Towards the end of the first session I experienced the worst boiled the fluid brake fade one could possibly have.
Hallett's second turn is the tightest turn on the track, a left hander entering from the end of the fastest straight. The turn is named the stop sign and if you continued straight you don't just go off the track in about 50 ft, down hill, you go into a grove of trees. Late in the first session I was headed into the stop sign, glanced down and was accelerating past 140mph. Moved to the outside and started watching the markers leading into the corner. My brake point came up and I hit it. To my surprise the pedal just went thump against the floor, No Brakes!!
Without taking time to think I just reacted and immediately pumped the pedal a couple of times...nothing. Without further hesitation I did a scandinavian flick sending the car sliding sideways pointed towards the inside of the turn. As I slid sideways it dawned on me that I seemed to be slowing pretty well, and maybe if I downshifted and got into the throttle I could make the corner and did just that. As i got back in the throttle i counter steered to keep the rear from coming around too much and amazingly enough the car continued it's sideways slide, but arced towards and into the apex. Keeping on the gas and counter steering I straightened it out and was exiting the turn heading down the next straight.
Did a quick glance back at the corner worker, he was standing up and giving me a thumbs up with both hands. I kind of coasted blankly through the next two turns not even going fast enough to touch the brake pedal. On the next turn I gingerly tested the brakes and sure enough, soft spongy pedal and almost not brakes. It wasn't until then I realized I had boiled my brakes. So I used the last three laps left in the session to just cruise around the track, letting everyone pass me, and NOT use my brakes so they could cool as much as possible.
Kim Crumb was riding as an instructor in the track prepared 928 directly behind through that corner. He came over to me after the session and told me he saw what I did, and wanted me to know, "You only have so many of those in you!"
So, with all this talk about brake bias, ABS, and trail braking and car setup, my fastest time through that corner was with no brakes at all!
My personal goal for the track that day in the 944 Turbo was practicing my late braking/trail braking on corner entry. However, I had put on new pads the day before and not taken the time to bed them in before the first session. Towards the end of the first session I experienced the worst boiled the fluid brake fade one could possibly have.
Hallett's second turn is the tightest turn on the track, a left hander entering from the end of the fastest straight. The turn is named the stop sign and if you continued straight you don't just go off the track in about 50 ft, down hill, you go into a grove of trees. Late in the first session I was headed into the stop sign, glanced down and was accelerating past 140mph. Moved to the outside and started watching the markers leading into the corner. My brake point came up and I hit it. To my surprise the pedal just went thump against the floor, No Brakes!!
Without taking time to think I just reacted and immediately pumped the pedal a couple of times...nothing. Without further hesitation I did a scandinavian flick sending the car sliding sideways pointed towards the inside of the turn. As I slid sideways it dawned on me that I seemed to be slowing pretty well, and maybe if I downshifted and got into the throttle I could make the corner and did just that. As i got back in the throttle i counter steered to keep the rear from coming around too much and amazingly enough the car continued it's sideways slide, but arced towards and into the apex. Keeping on the gas and counter steering I straightened it out and was exiting the turn heading down the next straight.
Did a quick glance back at the corner worker, he was standing up and giving me a thumbs up with both hands. I kind of coasted blankly through the next two turns not even going fast enough to touch the brake pedal. On the next turn I gingerly tested the brakes and sure enough, soft spongy pedal and almost not brakes. It wasn't until then I realized I had boiled my brakes. So I used the last three laps left in the session to just cruise around the track, letting everyone pass me, and NOT use my brakes so they could cool as much as possible.
Kim Crumb was riding as an instructor in the track prepared 928 directly behind through that corner. He came over to me after the session and told me he saw what I did, and wanted me to know, "You only have so many of those in you!"
So, with all this talk about brake bias, ABS, and trail braking and car setup, my fastest time through that corner was with no brakes at all!
08-13-2014, 10:52 PM
#56
Rennlist Member
Thread Starter
then, i did some threashold braking stops and then a couple with just standing on the pedal. standing on the pedal was like the "car was just giving way" when the abs kicked in. then i pulled the fuse and did it again. the braking force was so much obvious, just at the edge of lockup.
I dont know, but i could video tape a 100mph to stop with feel vs ABS , and show you the difference. I dont know where you get this information , but most anyone I speak with, in the racing world, and those that own the newer cup cars, agree. the new cars you can stand on the brakes and the abs takes care of it all. the older stuff, is almost dangerous, if you rely on it for stopping as well as feel.
another example. a long time ago, going into sears point turn 11 a little hot and in a close battle, i got well on the inside and ABS engaged and at the time i wasnt skilled enough to release and feel the tires again, as i said, it was like i hit a patch of oil or ice.
Now, you can just think im imagining things , or maybe i have some experience here that is worth taking note of.
remember long ago, we were arguing about the dual disc "H" adjusters... you were just as emphatic then, and you might understand, if you do the tests ive done, that i might be right here too.
if i am not, heck, it sure would be easier to brake if i can just engage ABS on all my critical turn approaches.
08-13-2014, 10:55 PM
#57
Rennlist Member
Thread Starter
The stop sign corner I described with no brakes was called the stop sign because it was not only the tightest slowest corner on the track it was at the end of the fastest straight. Hence the name Stop Sign, which I thought I described.
AND besides a turn tighter than the turning radius of the car, a tight chicane is another place where doing an out of control tank slapper is faster than a car "hooked up." And have an example to back that one up too. Had a course where I set fastest lap by .006 seconds against a full race prepared 914-6 that was used to setting FTD and I should not have been able to better. I was in my BMW X3 SUV. He watched my laps intently and had his pit crew timing both of us and told me I was beating him in the chicane he was quicker everywhere else on the course. I was treating the chicane like there was something in the road I was avoiding at the last minute before the chicane and throwing the car into a skid. I would then power through the tank slapping recovery from the skid. Timed right the tank slapping recovery is what carried me through the chicane without having to brake for it.
AND besides a turn tighter than the turning radius of the car, a tight chicane is another place where doing an out of control tank slapper is faster than a car "hooked up." And have an example to back that one up too. Had a course where I set fastest lap by .006 seconds against a full race prepared 914-6 that was used to setting FTD and I should not have been able to better. I was in my BMW X3 SUV. He watched my laps intently and had his pit crew timing both of us and told me I was beating him in the chicane he was quicker everywhere else on the course. I was treating the chicane like there was something in the road I was avoiding at the last minute before the chicane and throwing the car into a skid. I would then power through the tank slapping recovery from the skid. Timed right the tank slapping recovery is what carried me through the chicane without having to brake for it.
08-13-2014, 11:54 PM
#58
Rennlist Member
I learned with my GTS more than my 944 Turbo, probably due to the 500 or so pound difference in weight, technique of applying the brakes made a big difference in how quickly the car stopped AFTER ABS kicked in. And much LESS forgiving than the "Don't let it go into ABS" threshold braking I had been doing. To much to quick or to little then to much and it was exactly as you describe, felt like the car was just sliding. That's the difference in the newer and old ABS systems. I had to practice.
Honestly the chicane thing was a surprise. It was initially a mistake going in to hot because the brakes were so lacking on the SUV. Then I went with it and threw it into the slide just tapping the brakes to help get the rear started swinging.
Most of my experience is on Autocross courses and they are different than road courses. It is rare to see anything over 100mph.
Honestly the chicane thing was a surprise. It was initially a mistake going in to hot because the brakes were so lacking on the SUV. Then I went with it and threw it into the slide just tapping the brakes to help get the rear started swinging.
Most of my experience is on Autocross courses and they are different than road courses. It is rare to see anything over 100mph.
08-14-2014, 01:20 AM
#59
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Last edited by dr bob; 08-25-2014 at 07:07 PM. Reason: [Done]
08-14-2014, 04:49 AM
#60
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why do your experiences out weigh mine? i just took the 928 out for a 120mph to 50mph, several sequence exercise, and got to the fade point to get temp on the rotors with the temp sensor paint.
then, i did some threashold braking stops and then a couple with just standing on the pedal. standing on the pedal was like the "car was just giving way" when the abs kicked in. then i pulled the fuse and did it again. the braking force was so much obvious, just at the edge of lockup.
I dont know, but i could video tape a 100mph to stop with feel vs ABS , and show you the difference. I dont know where you get this information , but most anyone I speak with, in the racing world, and those that own the newer cup cars, agree. the new cars you can stand on the brakes and the abs takes care of it all. the older stuff, is almost dangerous, if you rely on it for stopping as well as feel.
another example. a long time ago, going into sears point turn 11 a little hot and in a close battle, i got well on the inside and ABS engaged and at the time i wasnt skilled enough to release and feel the tires again, as i said, it was like i hit a patch of oil or ice.
Now, you can just think im imagining things , or maybe i have some experience here that is worth taking note of.
remember long ago, we were arguing about the dual disc "H" adjusters... you were just as emphatic then, and you might understand, if you do the tests ive done, that i might be right here too.
if i am not, heck, it sure would be easier to brake if i can just engage ABS on all my critical turn approaches.
then, i did some threashold braking stops and then a couple with just standing on the pedal. standing on the pedal was like the "car was just giving way" when the abs kicked in. then i pulled the fuse and did it again. the braking force was so much obvious, just at the edge of lockup.
I dont know, but i could video tape a 100mph to stop with feel vs ABS , and show you the difference. I dont know where you get this information , but most anyone I speak with, in the racing world, and those that own the newer cup cars, agree. the new cars you can stand on the brakes and the abs takes care of it all. the older stuff, is almost dangerous, if you rely on it for stopping as well as feel.
another example. a long time ago, going into sears point turn 11 a little hot and in a close battle, i got well on the inside and ABS engaged and at the time i wasnt skilled enough to release and feel the tires again, as i said, it was like i hit a patch of oil or ice.
Now, you can just think im imagining things , or maybe i have some experience here that is worth taking note of.
remember long ago, we were arguing about the dual disc "H" adjusters... you were just as emphatic then, and you might understand, if you do the tests ive done, that i might be right here too.
if i am not, heck, it sure would be easier to brake if i can just engage ABS on all my critical turn approaches.
Your experiences are with one basic configuration on a tiny handful of tracks....and you want to trump me?
I could hardly care, but until you can figure out how to get your ABS and suspension to work together, you are stuck turning endless laps on a plateau that is way below the potential of the car.
However, perhaps your own ability and potential is maxed out and this is a great place for you to be.....
Your inability to listen to anyone is your limiting factor. For all your "pretend intellect", you refuse to listen and learn from anyone.
Here's the failure of your current logic:
Of course, when one tire goes into ABS (which by definition is the tire that is doing the most work), the car is going to feel like it isn't stopping as fast....the highest loaded tire just reached it's limit and has had to release some of the brake pressure, to keep from sliding. Duh!
The "trick" here, is to press harder on the brake pedal (instead of releasing the nrake pedal) and bring the other 3 tires into the same ABS mode (assuming that the suspension and bias are not so "rookied" up that it is possible to bring the other 3 tires into ABS.)
Your, or anybody else's, tiny little brain is never going to be able to modulate and slow the car faster than 4 tires all in ABS mode....which is completely controlled by a computer that is hundreds of times faster than your brain and your foot. Again, a "duh moment".
Your arrogance makes teaching you anything absolutely impossible....and this thread has reached the same point as all your threads...your ego thinks it surpasses all other knowledge.
I seriously have no idea why you even bother posting these threads and then refuse to listen to anyone....it's a complete waste of bandwidth and time!
The only thing I can figure out is that you are completely content being a mediocre driver with a mediocre car...and progressing any farther would exceed your abilities.