M104-AMG

iTrader: (8)

Do you know yet if the 328mm rotor and respective caliper will clear the stock 16-inch wheels ?

I'd really like to ditch my Wilwood project . . .

Thanks again for RB's and your hard work.

:-) neil

Howard Coleman

iTrader: (6)

neil,

immediate answer i don't know.

i do know that i threw a stock wheel on my M2 AP 13 by 1.1 rotor the other day and it would have taken a hand file and 5 minutes to make it fit.

as i understand, warren's 4 piston is of smaller general dimension V the AP caliper. further, the front rotor is 12.91 according to my calculator which is a touch less than the M2 rotor.

i am sure warren will give this every consideration along w the rear.

right warren?

howard coleman

turbogarrett

iTrader: (1)

If the rear caliper bracket is extended any farther than the '99 rz's you will not be able to fit the stock wheels. Kinda hard to see, with my shitty camera work, but here is a pic of mine with a stock wheel. The gap is paper thin and yes, they were filed down. I'll only be using them for the dragstrip, so that's enough clearance for me

Looks like I will be going with the stoptech fronts because I plan on tracking the car april 14 + 15th . Nice to see racing brake offers replacement "upgraded" rotors for the stoptech kits.

turb0x2

iTrader: (71)

Thanks for the update Howard! I will definitely purchase the front/rears in April

GoodfellaFD3S

iTrader: (213)

I'm glad to see this is becoming a reality . Any reason for the curved slot vs a straight slot?

jimlab

OEM '93-'95 rear calipers, or OEM '99+ rear calipers?

Howard Coleman

iTrader: (6)

please edit post 175 "there has been talk re a caliper for the RZ setup" to read:

"there has been talk of making another caliper mounting bracket to accomodate the 99+ rear caliper to the RB bigger rotor."

maybe a moderator could do an edit. TIA

the rear caliper mounting bracket will initially be cast so as to accept the standard pre 99 caliper. warren will look at the 99 plus if someone ships him same. while there are a number of 99+ out there the numbers needed to justify the investment for another caliper mounting bracket are probably not conducive to making a profit. why not just mount a set of pre 99 calipers? they probably go for close to scrap value and i believe have the same piston.

as to the comment about the rear rotor diameter situating the caliper so it interferes w the stock wheel... my guess is if this is true it may negate using stock wheels. it would be too much of a give-up to shrink the rotor. again, i do not know if this is a dealbreaker re the stock rear wheels firsthand.

howard coleman

Howard Coleman

iTrader: (6)

http://www.racingbrake.com/main/two_piece_compare.asp

you might be interested int the recently posted discourse re brake surface features as RB sees them. perhaps someone could post the page to this thread as it has some interesting pictures... and includes a RB patent.

howard

twokrx7

iTrader: (1)

I have the 99 calipers and they appear to be identical to the pre-99 calipers, just a different bracket to accomodate the larger rotor. Can anyone confirm this?

turbogarrett

iTrader: (1)

The rears are the same sized piston with different bracket, the fronts have different sized leading and trailing pistons.

Herblenny

iTrader: (13)

Thanks for the update Howard!

wanklin

iTrader: (2)

dis1

I have to say that I'm surprised that the original idea of a BBK using the stock calipers has been ditched. The Mandeville kit does it. So there is a bit of pad material that hangs over the edge because the caliper isn't ideal for larger diameter rotors. Big deal? I guess I'll get flamed for this but let's see where the price on this kit lands with their calipers.

hyperion

iTrader: (2)

Jumping on this thread. I really like to see innovation in this area, as I think it is the weakest area in the aftermarket for the FD. I have a couple questions:

1) Comparing the RB setup to, say, the N-tech/Stoptech/99RZ setup, what are the differences? (performance, weight, cost, etc.)
2) Is there any chance that RB will do a 6-pot front, 4-pot rear with a mechanical spot caliper? (this is what I'm personally looking for.)
3) Is RB planning a backing plate and ducting for the fronts? I don't care how nice these brakes are--any endurance racing setup should have ducts to stabilize temperatures.

I think the good news is that if we keep the piston sizes the same as stock and simply increase the diameter, we shouldn't need to change the master cylinder.

The one thing I should mention is that racing calipers generally use larger pistons to reduce spot boiling on the backside of the piston. Larger area means lower temperatures.

-ch

Black91n/a

One thing that I was wondering, with the rotors attached to the hat from both surfaces you end up with a gap there. What do you do when you want to use brake ducts? A portion of the air will leak out through that gap, reducing the effectiveness of the ducting (so it would seem). Is there something you can do to block up the holes to make the ducting work better, or does it not adversely affect it at all? Other than that issue it seems like a good way to do the joint.

Howard Coleman

iTrader: (6)

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.


to address a few questions:

the "Mandeville" option. firstly it really isn't an option as Roger has lots of other higher priority items on his plate including fishing.

the reason that the OEM front caliper won't work is that it will only fit an approx 11.8 inch rotor without being spread and machined. RB is not in the business of reworking OEM calipers. RB will design a purpose built 4 piston to optimally match up w the rear OEM caliper.

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.

i will try to run them into oblivion at Road America where i have held the GT3 track record "back in the day." we will be measuring temperatures, padwear etc. i will have a cockpit adjustable brake bias and we will develop and share the info.

should it be that the FD needs even more brakes in it's most tuned out format we will make the case and Warren will make his judgement. i do note that RB is releasing what i consider to be the ultimate brake solution for the Z06 and there just might be a crossover. the key word is "might."

Warren is spot on as to his judgement that his 328/322 setup w RB 4 piston front calipers should be evaluated first.

i have a distinct impression, based on Warren's body language, that i will be shocked at how much brake this package will deliver. (there is alot of positive performance margin in the unique rotor material and special pads for example). i could go on.... and on...

as to Hyperion's ?s... please re-read the first post in this thread as to RB brakes. i don't do comparison's nor w Warren. i have read all the 07 brake vendor's sales brochures as a friend brought them back from PRI a few weeks ago. at the moment we have no on-track RX7 data but RB does have lots from an NSX that ran very well at 2 Daytona races including a 6 hour. if you want to see some beautiful rotors check out the thread on RB's site w pictures of an EVO's rotors after 2nd in class at the 25 hour Dec Thunderhill race. #2.... maybe... see my comments above. #3 since the RB rotor is a center mount it does not lend itself to thru the center ducts. there are many many factors that determine rotor temp and most favor RB's centermount.

as to maintaining OEM bias thru the totality of the new brake system... absolutely, that's at the top of the list and that allows you to run the stock master cylinder.

it won't be long and i will be looking at turn 5.


stay tuned,

howard coleman

sherman2k

iTrader: (1)

So we are going to have complete front and rear BBK kit later on and also keep the E-brake for the rear? I am saving my money now for the GB.

Howard Coleman

iTrader: (6)

i love your brevity.

yes.

hc

hyperion

iTrader: (2)

Howard, I read a bit more carefully. Are you saying that the RB setup doesn't use cooling ducts because the rotor/hat design naturally inducts enough air through the center to cool things as efficiently as a duct?

-ch

Howard Coleman

iTrader: (6)

i wouldn't presume to speak to that point on a bottomline basis.

on my fd at my ride height when you bolt on 9.5 inch front wheels along w the rubber and go to full steering lock there isn't alot of room for duct hosing.

my car is a dual purpose street/road course car and i doubt if i will ever need ducts. one thing i do know is that if you don't plan to run hosed ducts to the center of the inner hub you will be way ahead w the RB centermount.

for my purposes i really like the centermounts.

contrast them to my current M2 AP setup... i see a completely closed off outboard area. No air entering there. i still have my OEM backingplate inboard so little air entry there... so really no air currently anywhere.

and i compare that to the new RB design where, after i remove the backingplates, there will be air entry from both sides.

given i don't plan to run ducts to the center of the inner hub, i figure the RB setup is the way to go.

the other factor is heat transference from the frictional surfaces. it is equal on the RB and one sided (think rotor warp) on most others.

your question is: might a track dedicated FD w ducts maybe have more air going thru the rotor? yes if designed properly..

could there be other RB superior design features that could offset this? maybe.

do take a look at the Evo rotor though if you want to see a happy rotor.... after 25 hours of racing w no ducts.

it will be interesting to see how things work out in 07..

regards,

howard

hyperion

iTrader: (2)

Sounds very interesting, Howard. I think temperature strip testing will set all these what-ifs to rest. I'm really looking forward to the data you're gathering. I was very close to going with a Stoptech/ducted setup, but like you my car is a street/strip hybrid. I'd like to simplify things and if I can get an aggressive hour of lapping on slicks, I'd be happy. Like you said, ducts are a pain on a street car...

-ch

hyperion

iTrader: (2)

BTW: anyone know what the effective radii of the stock brakes are? I've seen guesses, but no hard data.

-ch

hyperion

iTrader: (2)

I know I'm spamming this thread, so let me put my overall thoughts here. Howard, I'm interested in your feedback here as it has some application to what you're doing with your project.

First off, it turns out that most OEM braking systems are hydro-mechanically biased towards the rear under threshold braking. Now, I can see a lot of you scrolling down to the Quick Reply to tell me I'm an idiot, but just bear with me. Let's look at a bit of theory as applied to the stock FD system.

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

(For effective radius, I measured the annulus of each rotor and subtracted half that. This assumes that the piston is in the center of the pad height. I'm not sure about this, hence the question in the previous post, but it's a reasonable assumption.)

So, what's the 'balance' of the stock system? Well, with the above information you can make some calculations. On a pure mechanical basis, the force applied to the car is:

[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.

The 3000 lb car (with you in it) has a natural 50/50 weight distribution. The wheelbase is 95.5 inches, the center of gravity is about 18 inches (est.) and the maximum braking is 1.2 Gs. Based on this data, the weight transfer looks like:

* Front: 2179 lbs
* Rear: 821 lbs.

Or about 73% of the weight of the car on the front wheels. (This fits well with test data on other cars. Here's a nice article on calculating weight transfer under braking.)

See how the ratio of force (2.65) is much larger than the mechanical ratio of the brakes (2.03)? Curious. Let's keep going.

We now know that the front brake system can generate up to 2179 lbs before the front wheels will lock up, while the rears can only handle 821 lbs before lock.

On the FD, both the front and rear circuits are fed by the same (15/16") master cylinder. So the pressure in the master creates the same line pressure front and rear.

At what pressure will the wheels lock? Again, assuming the same Cf front and rear, the lock pressure is related to the required force and the mechanicals. Skipping some math, we find that the lock pressure of the front brakes is 997 psi, while the rear brakes need only 764 psi.

Say what? This is odd. Even though the front brakes provide a much greater raw force than the rears, the requirement of the front axle under dynamic braking is even higher. Or, to put it another way, as you raise the master cylinder pressure (with your foot on the brake pedal) the pressure will build. When it reaches 764 psi, the rear brake will lock--long before the fronts reach 997 psi.

Or, in other words, the balance of the system under threshold braking is rearward biased!. The rears will lock first!

Ok, not really. This doesn't happen in the FD because of the system described on P19 of the manual (shown below).



There is a built-in proportioning valve that has a knee at around 530-610 psi. After this knee, the pressure build is no longer 1:1, but at a lower rate. This allows the front circuit to reach lock pressure before the rear system does--without it, the rears would lock first.

Just about every modern car has one of these. It's on the 1972 Datsun 240Z, the 1993 MR2, and our car as well. Why? Because most of our braking isn't done at the threshold of grip. Under a leisurely 0.4 G stop, you only transfer about 250 lbs from the rear to the front. So you want to use more of the rear brakes for stability and optimal pad/rotor wear.

Okay, so, why am I bringing this up? Because I'm convinced that any serious brake kit needs to address the factory proportioning valve. Also, I want to point out that the rear circuit is already rear-biased, and that with an adjustable valve we would have more flexibility on what kind of brake combo to run.

Which leads me to my ultimate point: I'd love to see the following kit made available for the FD:

Front: 4-pot (32mm/36mm) calipers on 355 x 32mm rotors
Rear: stock (34.9mm) on 322mm x 20mm rotors (the proposed existing RB kit)

Based on some assumptions around effective radius, this setup would slightly shift the balance rearward. However, if the stock proportioning valve were replaced with an adjustable one, the original balance could be restored. And for track junkies, the valve will probably be necessary anyway for fine tuning.

We could also use 30mm/36mm calipers which shifts it just a little farther back.

An interesting thing to think about is every 1" you lower the CG on the FD, you transfer about 40 lbs (about 1.4% change) from the front axle to the rear under heavy braking. But each 0.1 G you gain under braking, it's 60 lbs in the opposite direction! So again, an adjustable valve would be nice for dialing it in.

This may also be key because the lock pressure of the RB rear kit should be around 610 psi. This means that the factory proportioning valve won't even be at its knee, meaning that the stock system may prematurely lock the rears.

So, that's my $0.02. Happy motoring. I'm looking forward to seeing the project develop.

Whew!

-ch

Black91n/a

Ummmm, the FD has 4 piston calipers up front, so that calculation is wrong...

A sliding caliper acts as though it's got 2 pistons for every one it actually has (fluid pressure acts on the piston and the bottom of the cylinder), so that number works.

hyperion

iTrader: (2)

Which calculation again?

-ch