FD New Brake Options
01-24-07, 06:03 AM
#201
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Originally Posted by hyperion
For those playing at home, the dimensions of the stock system are:
* Front: 2 x 36.1 mm pistons on 294 x 22 mm rotors, 122 mm effective radius
* Rear: 2 x 34.9 mm pistons on 294 x 20 mm rotors, 128.5 mm effective radius
[brake pressure] X [piston area] X [effective radius] X [pad Cf]
Assuming identical brake pressure and pad Cf, the comparison between the piston area and effective radius means that the front axle develops about 2.03 times the mechanical force as the rear.
So, why am I saying that the car is rearward biased? Let's look at what happens when the car dives under heavy braking with aggressive tires.
* Front: 2 x 36.1 mm pistons on 294 x 22 mm rotors, 122 mm effective radius
* Rear: 2 x 34.9 mm pistons on 294 x 20 mm rotors, 128.5 mm effective radius
[brake pressure] X [piston area] X [effective radius] X [pad Cf]
Assuming identical brake pressure and pad Cf, the comparison between the piston area and effective radius means that the front axle develops about 2.03 times the mechanical force as the rear.
So, why am I saying that the car is rearward biased? Let's look at what happens when the car dives under heavy braking with aggressive tires.
01-24-07, 07:59 AM
#202
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hyperion,
overall, an excellent post.
while there is an an incorrect labeling of the number of pistons the actual calculations are correct.
you do a nice job setting forth that longitudinal brake balance is a moving target based on G force, as well as explaining the dynamics of the OEM proportionng valve. you correctly, IMO, suggest that to maximize the brake system ontrack an adjustable (should be from the cockpit) brake proportioning valve is valuable.
your bias calculations are correct so you are inputting the proper amount of pistons front and rear. if you had used 2 and 2 pistons your balance would have been 52/48.
Warren is of course aware of all of this and i am quite sure he will properly size things as he has done for other cars...
interestingly most of the time when we talk about the benefits of lowering our cars we are thinking of latitudinal weight transfer in a corner. i have always said low is fast.... look what happens under braking to a lower car... less front weight transfer which allows you to run more rear brake. also, more static rear weight allows more rear brake. i run 53% rear weight.
howard coleman
overall, an excellent post.
while there is an an incorrect labeling of the number of pistons the actual calculations are correct.
you do a nice job setting forth that longitudinal brake balance is a moving target based on G force, as well as explaining the dynamics of the OEM proportionng valve. you correctly, IMO, suggest that to maximize the brake system ontrack an adjustable (should be from the cockpit) brake proportioning valve is valuable.
your bias calculations are correct so you are inputting the proper amount of pistons front and rear. if you had used 2 and 2 pistons your balance would have been 52/48.
Warren is of course aware of all of this and i am quite sure he will properly size things as he has done for other cars...
interestingly most of the time when we talk about the benefits of lowering our cars we are thinking of latitudinal weight transfer in a corner. i have always said low is fast.... look what happens under braking to a lower car... less front weight transfer which allows you to run more rear brake. also, more static rear weight allows more rear brake. i run 53% rear weight.
howard coleman
01-24-07, 03:09 PM
#203
Ah, thanks for the correction. The '2 x 34.9' is a typo--should be '1 x 34.9'! The calculations after that assume a single piston in the rear, of course.
My post is a bit confusing because I refer to the rear brakes as a single piston while I talk about the fronts as a 4-pot. In fact, when you do the calculations all you care about is how many pistons are on one side of the calipers. In other words, a single piston floating caliper behaves exactly like a two piston fixed caliper. The force generated by the single inboard brake pad must be balanced by the force against the force of the outboard pad since the two are linked and free to move radially. It's a bit counter-intuitive, but Newton assures it's right.
(The main advantage of fixed calipers is greater rigidity, higher thermal capacity, and easier pad replacement.)
The goal of most calculations is to determine clamping force. So when you see brake calculations that mix floating and fixed calipers, you generally consider half the pistons of a fixed caliper and all the pistons of a floating calipers--so you compare apples to apples! (There's Newton again.)
-ch
My post is a bit confusing because I refer to the rear brakes as a single piston while I talk about the fronts as a 4-pot. In fact, when you do the calculations all you care about is how many pistons are on one side of the calipers. In other words, a single piston floating caliper behaves exactly like a two piston fixed caliper. The force generated by the single inboard brake pad must be balanced by the force against the force of the outboard pad since the two are linked and free to move radially. It's a bit counter-intuitive, but Newton assures it's right.
(The main advantage of fixed calipers is greater rigidity, higher thermal capacity, and easier pad replacement.)
The goal of most calculations is to determine clamping force. So when you see brake calculations that mix floating and fixed calipers, you generally consider half the pistons of a fixed caliper and all the pistons of a floating calipers--so you compare apples to apples! (There's Newton again.)
-ch
01-24-07, 03:18 PM
#204
Thanks for the feedback, Howard.
I guess I'm hoping that in addition to the proposed 328mm fronts kit that RB might be convinced to try a larger 355mm front kit, and design it to work with a hydraulic proportioning valve.
What would be REALLY cool is a device that could marry this:
http://www.tiltonracing.com/content....ist2&id=38&m=b
To this:
http://www.tiltonracing.com/content....ist2&id=35&m=b
So that the bias valve could be mounted where the factory one is now but still be adjusted from the cockpit.
-ch
I guess I'm hoping that in addition to the proposed 328mm fronts kit that RB might be convinced to try a larger 355mm front kit, and design it to work with a hydraulic proportioning valve.
What would be REALLY cool is a device that could marry this:
http://www.tiltonracing.com/content....ist2&id=38&m=b
To this:
http://www.tiltonracing.com/content....ist2&id=35&m=b
So that the bias valve could be mounted where the factory one is now but still be adjusted from the cockpit.
-ch
01-24-07, 08:37 PM
#205
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as you may know the cockpit adj bias dial is designed to work w a dual master cylinder setup and i don't think that it could provide the substantial torque necessary to adjust a spring loaded proportioning valve.
that said i am going to mount my proportioning valve in the cockpit. i haven't figured it out yet but will during february.
howard
that said i am going to mount my proportioning valve in the cockpit. i haven't figured it out yet but will during february.
howard
02-03-07, 06:27 PM
#206
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Howard, for the future front and rear BBK for FD. What kind of disk do I need to order for the wheel? I am going to order Gramlight 57 pro next Monday. I need to know if I need A disk in all four wheels. I need to make sure your rear BBK is going to fit my wheel.
02-07-07, 12:41 PM
#207
Howard,
Are these rotors available yet?
To be clear, these are replacement rears in 322mm (aproxx. 12.75") diameter and roughly stock thickness that are meant to work w/ the OE 93-95 rear caliper with an extention bracket?
Are these rotors available yet?
To be clear, these are replacement rears in 322mm (aproxx. 12.75") diameter and roughly stock thickness that are meant to work w/ the OE 93-95 rear caliper with an extention bracket?
Originally Posted by howard coleman
RB is getting it done...
"We have just completed the design of rear big brake kit and tooling is also released."
designed to balance out the front BBKs running around w inadequate rear brake torque as well as to be the companion to a front rotor and RB caliper that will follow shortly.
i expect to run a set of the 328 X 28 front and 322 X 20 rear rotors along w the RB front 4 piston caliper and a relocated OEM rear caliper w Warren's special pads as soon as they are available.
"We have just completed the design of rear big brake kit and tooling is also released."
designed to balance out the front BBKs running around w inadequate rear brake torque as well as to be the companion to a front rotor and RB caliper that will follow shortly.
i expect to run a set of the 328 X 28 front and 322 X 20 rear rotors along w the RB front 4 piston caliper and a relocated OEM rear caliper w Warren's special pads as soon as they are available.
02-07-07, 01:09 PM
#209
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the first sets of standard sized (front and rear) 2 piece RB rotors arrive on Feb 10th. on schedule. they may be ontrack at Roebling Road feb 16-18th.
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
02-07-07, 01:23 PM
#210
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the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
I'm currently tracking my FD in the Nasa TT series about once a month and would pay for a beta version if available.
02-07-07, 02:45 PM
#211
Is that rear rotor size a match for the '99, or is it bigger?
Originally Posted by howard coleman
the first sets of standard sized (front and rear) 2 piece RB rotors arrive on Feb 10th. on schedule. they may be ontrack at Roebling Road feb 16-18th.
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
02-07-07, 05:01 PM
#214
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Originally Posted by ptrhahn
Is that rear rotor size a match for the '99, or is it bigger?
02-07-07, 08:55 PM
#215
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Originally Posted by howard coleman
the first sets of standard sized (front and rear) 2 piece RB rotors arrive on Feb 10th. on schedule. they may be ontrack at Roebling Road feb 16-18th.
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
the second FD brake option which is the roughly 13 inch front and 12.67 rear w extension brackets for the rear and a RB 4 piston front w bracket.... pads, lines should be available around april 15. pretty much on schedule.
howard coleman
02-08-07, 08:49 AM
#217
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"is the rear rotor size a match for 99/later?"
no, option 2, is larger and will not fit up w the 99/later caliper. just go find a set of OEM calipers and upgrade the system.
i do not suggest you do the math re a comparison of the 99/later rotor and the RB 12.67 rotor. there are a great deal of other factors in play other than the somewhat larger diameter. pls re-read post one of this thread. not the least of these factors is the differing brake pads that will be specially made to work w the different rotor alloy.
i am not attempting to "tell" you this. i am merely postulating. no RB brakes have turned an actual wheel on an FD. until they do all is engineering theory w the except of the fact that RB brakes have already demonstrated on the NSX and EVO that they perform as well as they should given excellent engineering.
i am greatly interested in how the stock dimensioned 2 piece rotors and compatible pads will perform. i personally think they may be the sleeper in the mix.
as mentioned they may be ontrack in about 10 days.
as to the ? re option 2 not having a bigger rear caliper... just to restate, the primary problem is the emergency brake. multiple piston caliper = no emergency brake within the caliper. option 2 should be on track and fully evaluated by me and perhaps others in april.
it is my firm belief that option 2 will provide what i think is potentially the strongest mass produced road course chassis w commensurate brakes.
for the first time.
stay tuned,
howard coleman
no, option 2, is larger and will not fit up w the 99/later caliper. just go find a set of OEM calipers and upgrade the system.
i do not suggest you do the math re a comparison of the 99/later rotor and the RB 12.67 rotor. there are a great deal of other factors in play other than the somewhat larger diameter. pls re-read post one of this thread. not the least of these factors is the differing brake pads that will be specially made to work w the different rotor alloy.
i am not attempting to "tell" you this. i am merely postulating. no RB brakes have turned an actual wheel on an FD. until they do all is engineering theory w the except of the fact that RB brakes have already demonstrated on the NSX and EVO that they perform as well as they should given excellent engineering.
i am greatly interested in how the stock dimensioned 2 piece rotors and compatible pads will perform. i personally think they may be the sleeper in the mix.
as mentioned they may be ontrack in about 10 days.
as to the ? re option 2 not having a bigger rear caliper... just to restate, the primary problem is the emergency brake. multiple piston caliper = no emergency brake within the caliper. option 2 should be on track and fully evaluated by me and perhaps others in april.
it is my firm belief that option 2 will provide what i think is potentially the strongest mass produced road course chassis w commensurate brakes.
for the first time.
stay tuned,
howard coleman
02-08-07, 12:41 PM
#218
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I would like to know how much of a difference between option1 & option 2. Basically is it worth loosing the emergancy brake if it's only a slight gain in stopping power. I have allways wanted option one beleiving if done correctly it could be better then other company's bbk's (simpler, easier, cheaper, sleeper). Is there no comparion feedback on these two fro the RX8, EVO, NSX testers? If no one has physically tried both setups then what does the engineering data say the extimated difference would be?
02-08-07, 01:36 PM
#219
>>Basically is it worth loosing the emergancy brake if it's only a slight gain in stopping power.
I just want to point out the clarification of stopping 'power' vs stopping performance. Howard and other road racers already know this and can probably make a more articulate version of the babble I am about to spew.
I just want to clarify that putting on bigger brakes does not really mean you get more stopping 'power', power is not a good word to use as it implies you can stop in a shorter distance than the previous bakes on the car, when in reality that is determined by your grip (tires to road surface), not your brakes.
Instead think of it as a measure of consistent braking performance rather than braking 'power'. In other words, what you want is be able to achieve maximum braking performance over and over and over, lap after lap, with the minimal amount of braking performance loss due to heat.
This is the main benefit of a larger and/or better made brake kit can provide. The stock system can only mitigate a moderate amount of heat before the performance quickly degrades, however a upgraded braking system (larger, better design, et) has the ability to manage a much larger amount of heat and thus maintain braking performance consistency as more and more heat is generated from using the brakes over and over again, as in a road racing situation.
Its not about the first time you hit the brakes on the track, its about the 40th time you hit the brakes. Idealy you want that 40th time to be just as consistent as the first time, and that is what a proper brake upgrade can give you. I am greatly oversimplifying things here, but you get the idea.
Since the rotors and calipers tand to be larger, et, et, ...yes it does provide more clamping force, et, et... but it is a misconception that this diretly turns into more stopping 'power', ... no matter how massive your brakes are, you can not stop better than the grip your tires will provide. On the other side, if you upgrade tire size and compound, then you may reach a point where you are out 'gripping' your brakes as well, but that ratio is typically so one-sided that it rarely happens.
A great example is comparing what we have seen between my race car and Andy's street/track car (he is gooroo on the forum). My race car has massive brakes in front and jspec rears, and Andy has stock brakes. Both cars brake about the same in terms of stopping distance, however his brakes over heat within a few hot laps and he has to back off, where I can go hard to the very last lap with minimal braking performance loss. Again, the benifit is not that I am able to out brake him in one particular braking zone, but rather that I can out brake him over the entire session. On the 15th lap I can still be threshold braking where a car with stock brakes has to coast for a few laps to cool the brakes down or risk putting a caliper piston through a pad backing plate (Andy has done this twice i think...heheh) :-)
Again I am oversimplifying as there are other benefits and other complexities involved, however from my perspective, better braking performance consistency is what you should expect from a bbk.
And they look sweet as hell too!!!
I just want to point out the clarification of stopping 'power' vs stopping performance. Howard and other road racers already know this and can probably make a more articulate version of the babble I am about to spew.
I just want to clarify that putting on bigger brakes does not really mean you get more stopping 'power', power is not a good word to use as it implies you can stop in a shorter distance than the previous bakes on the car, when in reality that is determined by your grip (tires to road surface), not your brakes.
Instead think of it as a measure of consistent braking performance rather than braking 'power'. In other words, what you want is be able to achieve maximum braking performance over and over and over, lap after lap, with the minimal amount of braking performance loss due to heat.
This is the main benefit of a larger and/or better made brake kit can provide. The stock system can only mitigate a moderate amount of heat before the performance quickly degrades, however a upgraded braking system (larger, better design, et) has the ability to manage a much larger amount of heat and thus maintain braking performance consistency as more and more heat is generated from using the brakes over and over again, as in a road racing situation.
Its not about the first time you hit the brakes on the track, its about the 40th time you hit the brakes. Idealy you want that 40th time to be just as consistent as the first time, and that is what a proper brake upgrade can give you. I am greatly oversimplifying things here, but you get the idea.
Since the rotors and calipers tand to be larger, et, et, ...yes it does provide more clamping force, et, et... but it is a misconception that this diretly turns into more stopping 'power', ... no matter how massive your brakes are, you can not stop better than the grip your tires will provide. On the other side, if you upgrade tire size and compound, then you may reach a point where you are out 'gripping' your brakes as well, but that ratio is typically so one-sided that it rarely happens.
A great example is comparing what we have seen between my race car and Andy's street/track car (he is gooroo on the forum). My race car has massive brakes in front and jspec rears, and Andy has stock brakes. Both cars brake about the same in terms of stopping distance, however his brakes over heat within a few hot laps and he has to back off, where I can go hard to the very last lap with minimal braking performance loss. Again, the benifit is not that I am able to out brake him in one particular braking zone, but rather that I can out brake him over the entire session. On the 15th lap I can still be threshold braking where a car with stock brakes has to coast for a few laps to cool the brakes down or risk putting a caliper piston through a pad backing plate (Andy has done this twice i think...heheh) :-)
Again I am oversimplifying as there are other benefits and other complexities involved, however from my perspective, better braking performance consistency is what you should expect from a bbk.
And they look sweet as hell too!!!
02-08-07, 01:45 PM
#220
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Originally Posted by howard coleman
i do not suggest you do the math re a comparison of the 99/later rotor and the RB 12.67 rotor. there are a great deal of other factors in play other than the somewhat larger diameter.
Originally Posted by howard coleman
not the least of these factors is the differing brake pads that will be specially made to work w the different rotor alloy.
02-08-07, 02:05 PM
#221
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I want to add the bias note to Damian's excellent points. Getting the bias right is critical to that "first stop" performance, and the wrong upgrade can improve consistency while harming braking force. Howard's current setup is a great example of this (GooRoo's car should be able to outbrake Howard's into the first corner), which explains why HC started down the RB path.
02-08-07, 03:33 PM
#222
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Eggie is correct. if you run big brakes on the front and stock brakes on the rear you move 8% from the rear and add it to the front. result: rears don't work as well as stock. fronts have too much force as Damian properly points out and the end result is less brake performance.
just to make sure i am clear w Goracer: the emergency brake is of course part of options 1 and 2.... as to the differential, i have an XL spreadsheet and it grinds out better numbers of course for option 2 but there are other factors in play. of course option 2 will create more braking force and maintain it... how much more? that's what we will soon discover as option 1 may be ontrack in 10 days.
howard coleman
just to make sure i am clear w Goracer: the emergency brake is of course part of options 1 and 2.... as to the differential, i have an XL spreadsheet and it grinds out better numbers of course for option 2 but there are other factors in play. of course option 2 will create more braking force and maintain it... how much more? that's what we will soon discover as option 1 may be ontrack in 10 days.
howard coleman
02-08-07, 05:10 PM
#223
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Sounds great Howard. *If* these brakes will fit with my Fikse FM5s, I'm extremely interested. For comparison's sake, the wheel just barely scrubbed the front edge of the mandeville caliper (where it says 'mazda) and the techs over at Fikse tell me the Stoptech caliper will overlap the wheel by 1mm. I'm trying not to use the 4mm spacers I have sitting in the garage for fear of chewing up my fenders.
02-08-07, 07:10 PM
#224
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^ This version may interest you then. I may get the Enkei's if the Buddy Clubs fall through but I really beleive the RB OEM size at worst will be negligably less efiective then the RB bbk and actually better then most bbk's. Allthough they are affering aluminum calipers.
http://www.racingbrake.com/Fits_Enke...set_s/4411.htm
http://www.racingbrake.com/Fits_Enke...set_s/4411.htm
02-08-07, 07:35 PM
#225
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Originally Posted by GoRacer
^ This version may interest you then. I may get the Enkei's if the Buddy Clubs fall through but I really beleive the RB OEM size at worst will be negligably less efiective then the RB bbk and actually better then most bbk's. Allthough they are affering aluminum calipers.
http://www.racingbrake.com/Fits_Enke...set_s/4411.htm
http://www.racingbrake.com/Fits_Enke...set_s/4411.htm
