Howard Coleman

iTrader: (6)

yes. stock 93-95 calipers w bigger rotors is job 1.

howard

sdoow

Dave sent me these (rotor) pics prior to his departure to airport and I lost contact on him so I couldn’t help Howard questions but thanks to Gooroo’s digging into those stories. Dave deserves a break as he ended up in hospitable briefly due to the extreme endurance he had to sustain from the race (only him and Ralph run 25 hours – Normally 4 drives)

This EVO originally comes with Brembo 4 pot front (using D1001 pad) and 2 pot rear (using D961 pad) calipers which has been upgraded to RB’s 4 pot caliper (using D647 pad).

WORKS is one of RB’s dealers who has extensively tested all the major brands' brake products and ended up with us. The rear pads are Hawk’s HT-10, and the front is a racing compound that RB has provided for WORKS to test in various track events including this 25 hours. According to Dave at the end of the race he still has 15% front and 10% rear friction left.

Both compounds are proven to be an excellent companion with RB two piece rotors and we are glad to sponsor this exceptional brake package that not only saves their lap time but also gave them the needed confidence to brake hard and late to win the race.

p.s. We are completing our 6 pot caliper kit (14” two piece rotor) for EVO that will fit under 17” wheel (normally requires 18”) to replace Bermbo’s 4 pot front - Highly demanded kit but still not available in the market. RB listens and responded to their need and this kit will be tested in 2 weeks and release in about 6-8 weeks. Both
RB street and track pads will be offered in early spring on aluminum calipers applications.

Warren

jimlab

Not to rain on the parade again, but...

The why is obvious; stock replacement rotors represent the biggest potential market segment. However, it's not something that we're currently missing and can't get elsewhere.

If a brake company truly wanted to serve the FD community by providing something much needed and not previously available, they'd produce an OEM-style floating single or fixed 4-piston rear brake caliper that allows the use of a 12.8-13.0" rear rotor, balances piston area front to rear with the common 13.0" front brake kits already available (and that most track drivers already have), and retains OEM parking brake functionality. Obviously the potential market isn't nearly as large, but that's what we really need.

In 10 years of FD ownership, the only thing I've seen that comes remotely close is Mazda's '99-spec rear caliper; unfortunately, there's no increase in piston area. M2 Performance was supposedly going to provide a 4-wheel big brake system that retained the parking brake but was never able to deliver. At this point, even a bracket to mount another manufacturer's larger rear caliper with identical parking brake functionality (Corvette?) would be a major step in the right direction, assuming piston area was compatible.

Until someone solves this problem, it's hard for me to get excited about stock replacement rotors, no matter how much better they are than what's currently available.

88GT

Ditto! 17in. wheel

Great reading. Thanks to all

wanklin

iTrader: (2)

Perhaps the viability of an E-brake extension could be investigated?

94RHDFD

iTrader: (3)

Has anyone seem this: http://www.revolutionbrake.com/index.html scroll to the bottom of the page the "Mr. Parker"

sdoow

In the past years we have observed that the newer models the larger the brake rotors become. See the trend:
http://www.racingbrake.com/main/oe_c...it_compare.asp
As to RX7 rotors we have gone through these (size) changes and here are what we have made:
Year RB P/N Size (front rotor)
79-83 9171 227x18
84-85 9175F 227x18
86-88 (4 lug) 9178F 250x22
86-92 (5 lug) 9074 276x22
93-95 90411/2 294x22
Not to say we are the only brake company around for sometime but we know we are probably the only brake company still exists today over 20 years and still makes and tracks all these brake changes on RX7 and continuing to RX8.
We build our brake upgrade by following motor companies’ act and believe brake power (torque) essentially lies in the rotor size (brake leverage) and the friction (brake pad), not master cylinder nor piston sizes like other big brake companies make you to believe. We have evaluated and compared numerous rear set ups (from other car makes) to RX7 and found out the rear piston is not inadequate and is in fact proportional to front caliper so our approach is to build a larger brake kits with proportional increase of rotor size (front and rear) retaining the OE calipers for the most of folks and we are confident it will work by our experience, but if you know someone already made the same set up available you should share it with other RX7 owners, and if you have those great idea in how the rear calipers should be made you should approach those big names like AP, Alcon, Brembo or Stoptech and express your expectation so the RX7 community can be better served.

Warren - RB

jimlab

Thanks for responding Warren.

Actually, master cylinder size and piston area does affect brake torque.

Brake torque = effective rotor radius (inches) * clamping force (lbs.) * coefficient of friction / 12

Increasing or decreasing the line pressure or piston area (clamping force) increases or decreases brake torque even without a change in rotor diameter or pad compound.

When upgrading to 13.0" rotors in the front with aftermarket calipers, you shift brake bias towards the front. You cannot offset the change in front brake bias simply by increasing the rear rotor diameter unless you also increase the piston area of the rear calipers. That's why '99+ spec rear calipers with 12.4" rotors aren't really a balanced solution for a 13.0" front brake kit, but it's certainly better than stock diameter rotors.

When compared to the stock front calipers, sure. How about when the front caliper is an AP Racing CP5200 (2 x 38.1mm + 2 x 41.25mm)?

The stock '93-'95 piston area ratio is 2 x 36.1mm / 1 x 34.8, or 2.07:1 F/R.

With '99+ spec front calipers (2 x 33.9mm + 2 x 38.1mm), it's 1.99:1 F/R.

With AP Racing calipers in front, however, it changes to 2.28:1 F/R.

Ignoring the change in rotor size for the moment, are you stating that the change in piston area would have no effect on brake torque bias and the stock rear caliper is still adequate?

Which is fine, if everyone is happy being limited to 12.4" rotors and buying '99+ spec calipers. Some of us already have a considerable amount invested in aftermarket 13.0" front brakes and would like a matching rear solution.

Thanks, but obviously none of them would have an interest in producing an OEM-style caliper with an integrated parking brake for a potential market as small as the 3rd generation RX-7. I guess we can add you to that list.

GooRoo

iTrader: (4)

I'm confused, you do know that the main project here that howard is interested is the 'new' racing brake system for front and rear right? RacingBrake already has stock size replacement one and two piece rotors for sale on their site.

They are going to take the rear caliper, re-cast the non-piston part to move it out further, and try to run a 324mm rotor in the rear. That is what they are terming re-using the 'stock rear caliper' It's not just a replacement of the rotor itself.

I believe based on the numbers in this thread that the proposed setup would be substantially more brake torque than even the '99 spec 12.2" rotors.

The next step (not really started yet) is that they would fab a front kit, with ~ 13" rotors and proportional overall torque so that the stock master cylinder (or a 929 if you want a harder pedal) and proportioning valve (and ABS) are all basically unaffected. This would also attempt to re-use the 'stock front caliper' however that remains to be determined once the rears are done. And people could forgo this alltogether if they already have some sort of 13" calipers that they can balance manually, or that they believe will balance correctly with the stock master cyl/abs/prop valve setup.

Some people on the thread are also asking about two piece front and rear rotors from them for the '99 setup, but that is a separate issue that I haven't heard is something they are considering yet.

I think we need a summary email on everything discussed so far with regard to RacingBrake setups and potential setups from Howard (or Warren) to get us all back on the same page.

wanklin

iTrader: (2)

I think it's clear that creating a custom rear setup is just not a financially sound avenue for Warren to take unless it can be built to be cross combatible with other applications.

The pragmatic solution is to settle for the bracket extensions stock calipers and make them adaptable to the 99spec calipers if at all possible. With that being said, before any final sizing decisions are made we should make sure that the E-brake cannot be easily extended.

Eggie

Those ratios compare piston diameter.

jimlab

If you read back a page or two, you'll notice that Rishie stated that their only intention at this time was to provide stock diameter ('93-'95) replacement rotors.

Nowhere have I seen a commitment to providing anything else, including '99+ spec rotors, which is why I asked for clarification 3-4 posts ago...

Yep, you're right. I originally intended to compare area and then decided to leave it as simple as possible and compare diameter only. My mistake.

The stock '93-'95 piston area ratio is 2047.08 mm^2 / 951.15 mm^2, or 2.15:1 F/R.

With '99+ spec front calipers (2042.68 mm^2), it's 2.15:1 F/R.

With AP Racing calipers in front, however, it changes to 2.60:1 F/R.

Better?

wanklin

iTrader: (2)

see above ^

wanklin

iTrader: (2)

Typo above: Howard said rotor when he meant caliper.

jimlab

Yeah, I saw Howard's post about 324mm rear rotors. That's not a post by the supplier or the vendor. As far as I know, Howard's not manufacturing or selling anything.

Regardless, it still won't balance the brake torque bias for those of us with existing aftermarket 13.0" front brake kits.

wanklin

iTrader: (2)

Yes, but it can be safely assumed that he did not take delivery of the stock mounting brackets to simply use them as paper weights ;o)

I feel your pain Jim. Maybe you can get a GB interest thread together and show RB that custom rotors are financially feasible. That would certainly be a sweet option....

jimlab

I've sent a lot of stock parts to vendors over the years without reaching a positive result and I don't have an earful of kisses from said vendor, so frankly, I'm not overly excited... especially since I've seen nothing so far that is of any benefit to me or people like me.

If stock calipers (or their pistons) are reused front and rear it eliminates a lot of the cost for the vendor and eliminates any imbalance in piston area and clamping force. Proportionally increasing the diameter of the front and rear rotors also reduces or eliminates a potential imbalance in brake torque. So far, so good. If it pans out, and IF you're one of the people who doesn't have anything invested in brake upgrades yet...

However, there are a lot of FD owners who were part of the Precision Brakes/RX-7 Store group buy and now have '99+ spec rotors and calipers, either front and rear, or rear only. There are also many of us who have aftermarket 13.0" front brake kits. We're not interested in replacement rotors or calipers unless it means a vast improvement in performance, or more realistically, a chance to resolve an imbalance in brake bias. I haven't seen anything so far that indicates to me that there's any interest whatsoever in taking us into consideration.

Apparently, I mistakenly believed this thread was a chance to share what we want/need with a vendor interested and capable of providing it. It's now become quite obvious that they have no intentions of producing something that works in conjunction with parts purchased from anyone but themselves. Maybe that's being unfair, but that's what I've seen so far. Frankly, I'd like to be proven wrong.

GooRoo

iTrader: (4)

Ah ha, now I understand. I think you are correct, there's nothing so far that says that all the random 13" or similar front brake upgrades that people have made/purchased over the years will be balanced by this rear upgrade.

<<<Jimlab skip this part as you probably already know it all but I'm clarifying for others>>>

What is true, is that this potential setup (RB modified stock 93-95 caliper + 2 piece rear RB rotors) will have more rear brake torque and capacity than anything that has been known to be offered for the rear. Therefore, if the problem that you (or anyone else) have is that you have done the numbers and know that you do not have enough rear brake, that this new RB setup may be of help to you.

For everyone else who still has stock brakes, or is willing to sell whatever upgrade they may have, the front and rear setup - STILL UNDER DEVELOPMENT - may end up being the way to upgrade all around, and still maintain proper balance.

<<< END Jimlab skip part>>>

I think that they believe that the largest remaining market for brake upgrades would be the front and rear balanced kit, so that is what they are focusing on. (Of course as stated, they already have OEM size 1 and 2 piece rotors for sale) Perhaps we could run a poll to check this? I would suspect that after that kit is done, that some numbers could be run for other front brake upgrades, either by RB or yourself or whomever and potential custom configurations (based on the main version) could be done.

I think that Howard and Rishie are both working with warren, Howard from a more personal perspective with regard to his car, and Rishie from a sales/marketing perspective. I could be wrong on both counts.

sdoow

In our point of view the performance brake market has long been misled by those big names that making aluminum caliper big brake kits, as they actively promoting their standard BBK (mostly front only) they never address the possible bias issue resulting from the front BBK installation and left the rear compatible kits unattended.

Ample incidents everywhere, including those RX7 owners who failed to calculate their numbers “prior” to their purchase of these BBK. Also, this one was posted on Corvette Forum from another brake company informing their customers about whether they need to purchase a compatible big rear brake kit or not.
http://forums.corvetteforum.com/show...4&postcount=49

RB builds its BBK fundamentally different from others, we always build rear and front at the same time, and we build from OE configuration up, and our upgrades are progressive as the owners feel the need and the investment is incremental. For example we have customers from RX8 and 350Z currently own RB OE caliper big brake kits (with RB two piece rotors) now can upgrade to aluminum calipers kits and all they have to do is to purchase the calipers and adaptors. http://forums.racingbrake.com/viewtopic.php?t=501

This incremental upgrade can work for the same to RX7 owners who want to eventually upgrade to the full track brake package.

We have scheduled to make those RX7 brake just like we did for Corvette and NSX. Whoever is interested in those brake upgrades please continue your feedback and comments by posting here.

Here is the summary of the upgrade.

GooRoo

iTrader: (4)

Thanks for the update.

dis1

Jimlab,

I think there are still a lot of people out there that have a front only BBK that could use the rear only deal being considered here. There are also people like me that never upgraded because I didn't see a cost effective AND balanced choice available. I envision that 4 rotors (2 piece or normal 1 piece) and 4 extending brackets could cost much less and be better than your standard front only kits that sell for around 2K.

Personally I think that is exciting news!

TRISPEEDFD3S

iTrader: (26)

This seems very promising!

moconnor

iTrader: (14)

Am I right in concluding that the price will be in the ballpark of $1k for two piece rotors and caliper relocation hardware for all four corners?

Howard Coleman

iTrader: (6)

i am pleased re Warren's first step as to offering an upgrade path that for the first time balances out the FD.

and it is a path.

the first step is to custom design FOUR rotors for our cars.

they are two piece, cast left and right so the air vanes actually work. the center mount rotor transfers an equal amount of heat from the inner and outer frictional surface to mitigate warpage. the rotors are made from Warren's own mix of materials and both the molds and casting are completely controlled by him. these are not just another set of larger rotors. if you have been reading the thread you know that.

it appears that the size will be 12.75 front and 12.67 rear... approx equal in diameter to retain the OEM 68/32 torque at the wheel balance.

since the rotors are larger there is mechanical advantage v stock:

frictional surface area increases 11.2%

leverage increases 9.8%

rotor mass increases 19.6% in front and 11.2% in the rear. (doesn't change OEM bias)

and all this functions approximately 150 degrees cooler according to the NSX racers and their pyrometers.

in addition very little has been said about brakepads. warren is planning to make, in partners w Hawk, special street and track pads which will work very well w his rotor material.

special cast caliper mounting brackets will allow the reposition of the OEM calipers which will work well. SS brake lines complete the package.

step 2 is to offer RacingBrake calipers which will fit the rotors.

step 3 will be to offer a racing setup which will not have the E brake and will feature larger rotors and calipers.

all specifically for the FD. all properly sized. all bolt in w no hacking around.

so that's the deal.

very soon one of the greatest sportscars ever mass produced will have a custom tailored FOUR WHEEL brake system that will perform to FD standard.



Here’s warren’s rx8 package…


rotor size matters


looks good...... is good


howard coleman

Kento

Looks good...and will be good, as long as they'll fit underneath my 17" FM-5 Fikses...