Sorry, no photos... we're in "super-secret development mode" right now...

Soon though... very soon!

 

I haven't read through all of this but wanted to interject a couple of points.

1. Remember that 4 larger pistons can consume the same amount of fluid as 6 smaller pistons. The increase in piston qty will aid in more even/stabler pad contact. I think this all comes down to the engineering of the system. Is it a universal caliper or one specifically designed for an application.

2. A few things I've highly regarded in my Endless 6Piston Brake setup.

Phenomenal Pedal Feel, WAY WAY Better than stock. Proof that 6piston can work.

Explanation:

Staggered Piston Diameters
Staggered Piston Arrangement

Will these calipers have the same setup?

Will these calipers use an off the shelf OEM Pad, like Stoptech and RacingBrake?

I greatly apologize if those questions are redundant.

I'm happy with the OEM Size Rotors to tell you the truth.

If you came up with:

1. Affordable OEM Caliper Replacement Kit Front and Rear it would sell well.
2. This way the client has several options for Rotors and Brands

Key Issue is definitely the retention of the ebrake function. It will be interesting to see if they will cast a whole new caliper that contains this mechanical function.

For those of you who want a Rear Caliper you can always move to a

HYDRAULIC EBRAKE, in theory i don't see why this wouldn't work. It's gonna be as good as the parts and your installation. You basically terminate the mechanical ebrake and replace it with the hydraulic one. This would then T into your hardlines leading to the rear calipers. I assume it has some type of piston/hydraulic booster to hold the pressure.

Rishie

 

I agree with Endless Rotaries. I'm not a big fan of the two piece design. After speaking with the guys over at Stoptech they brought to my attention that the weight savings from the aluminum hat is not as impacting as one would think since due to the laws of physics the weight reduction benefits would be better felt if the outter diameter of the rotor was lighter and not the inner. Please don't ask me to explain further as I'm just passing along what was told to me. My personal preference would be an upgraded red caliper (front & rear inlc. ebrake) and slotted oem size 1 pc. rotors. Parts would be more readily available and I won't have to worry about proper torquing of the aluminum hat bolts.

My 2 cents.

 

yes need photos Dont forget us that cant make SSX

 

Two popular misconceptions in one post...

First, not only does a lighter rotor still accelerate faster rotationally, it allows the suspension to respond to vertical inputs much faster. Less mass anywhere in the system makes the strain on the power steering easier too (spin a bicycle wheel in your hands and try to turn it left and right, high school physics folks).

Simply, a company like Stoptech, who might have invested in having a Chinese company cast a one-piece 13" brake rotor will WANT you to believe that there's not much savings to be found here. There IS a savings and it CAN be proven.

BTW-a properly torqued and Loc-tited hat bolt is no issue at all. I'm sure all 12 on each rotor will be torqued to the proper 58 ft/lbs of torque necessary to retain them. If we use the Wilwood parts, they'll likely be safety-wired too. Or at least they could be.

 

1. It is a universal caliper but we've requested a pisto size change to make it work well with the RX-8.

2. It will use a "staggered diameter" piston setup.

3. They will use an off-the-shelf pad, but Wilwood makes compounds from street to the most brutal race conditions imaginable.

OEM rotors are NOT compatible with aftermarket calipers. They are an oddball size.

 

Good correction, with qualification. The bicycle wheel analogy points to rotational inertia. To really understand the points under discussion, the concept of rotational inertia must be separated from the concept of simple mass.

This post really isn't meant to be a thread-jack at all. I'm not sure what is meant to be implied by the quote above, because it doesn't point to anything that's true or relevant to the discussion in this thread. I've had friends at StopTech for about six years now, and have a pretty good understanding of their products. First off, as long as the discussion is big brake kits, let's keep it on big brake kits. StopTech's two options for the RX-8 use 328mm (12.9-in.) or 355mm (14.0-in.) rotors. Both are two-piece, floating assemblies with anti-rattle hardware and 7075 aluminum hats. The rotors in these kits are identical to those used to win many races in World Challenge TC and GT.

StopTech also has a program it calls SportStop, which includes the stainless steel lines and drilled or slotted OE-style, one-piece rotors. Many of the SportStop rotors do indeed come from China. But guess what? There is literally zero manufacturing of aftermarket OE-style replacement rotors in the US today. The vast majority of it comes from China, with some coming from other Asian sources and a little from Mexico.

Quite the contrary to what PhotoMunkey implies, the weight savings of the aluminum hat is discussed in StopTech's promotional materials. Additional benefits it promotes about its BBK rotors are improved cooling of the outer face of the disc due to the AeroHat's directional standoffs, and the fact that a rotor that is able to expand radially (floating, not fixed-bolted) will maintain greater parallelism of the two friction plates through all operating temperatures.

I suspect the original misunderstanding on the part of AGLRX8 comes from the subtle and complex nature of the discussion. The benefits of reduced unsprung mass described by PhotoMunkey are real and unqualified. A car with less unsprung mass will ride better and stick to the road over bumps better.

I would speculate that people on the phone at StopTech have been thinking a lot about moments of inertia lately, possibly to the point of over-emphasis, because they are beginning to get serious about marketing the ceramic rotor technology they've been working on.

What was described to AGLRX8 was the phenomena of rotational inertia. The effect of a bit of mass on rotational inertia is proportional to the square of the distance of that mass from the axis of rotation. That means moving a piece of iron from four inches away from the axle centerline to eight inches away will not double, but quadruple its contribution to rotational inertia. This is the main reason a car with 17s may accelerate measurably faster than the same car with 18s, even if the 18s are equally lightweight.

So back to StopTech soft-selling its products. If you go from a 288mm Volkwagen GTI stock disc (I just made that measurement up) to a 328mm disc in a BBK, even if the 328mm disc weighs less because of the aluminum hat, it will probably have quite a bit more rotational inertia. In fact, this was once measured as a couple hp loss on a Dynojet - on TV - so StopTech is a little sensitive to the point. With a 355mm rotor, the effect would be much greater. You might be able to measure a reduction in acceleration when you put a BBK on your car, even if the overall unsprung weight is reduced. No BBK company can claim any high ground there as long as the rotors are made of cast iron, because they're all in the same boat with Isaac Newton (I hate that guy sometimes). I'll still take the benefits of the BBK, because I care about decelerating on lap 10 of Buttonwillow.

Fortunately, RX-8s are RWD, so you don't have to worry about losing hp on a Dynojet when you install a BBK on the front axle.

With an RX-8, where the OE Sport rotor is 323mm, going to a 328mm rotor may come out close to a wash on rotational inertia. The 28mm disc is 4mm thicker than OE RX-8 Sport discs, so there is probably a little more metal farther out. You'd have to build the assembly in a CAD program and have it calculate the rotational inertia, then compare it to a model of the stock rotor. The thicker rotor will have a lot more air going through it to cool it.

I hope this helps people understand the technical issues better.

PhotoMunkey, you can have your thread back now.

 

You have over simplified the rotational inertia by leaving out leverage, i.e. the distance from the rotor center to the outside edge. Granted, going from 323 to 332mm (in this case) will move mass outwards, the overall weight of the rotor drops from just over 18 lbs to 12.3 lbs! That is a SIZABLE reduction of weight; over 5.5 lbs. Now with the new aluminum hat and hardware we're looking more like 14.5 lbs, but still, a very large difference for just one component.

The engine must accelerate two front rotors, and no, this doesn't show on the dyno, but can certainly be measured by a stopwatch at the track. Any weight that the engine doesn't have to push will make the car faster at the end of any straight-away.

Now, in regard to steering, spinning 18lbs of mass versus spinning 14.5 lbs of mass at a slightly wider diameter... I'm not sure of all of the physics involved but I'm darn certain that the power steering WILL have an easier time turning the 14.5 lbs.

As far as suspension control, any bump will move 14.5 lbs faster than 18 lbs, making the load on the tire easier, which enhances the tire's grip on the road. The less you upset the tire by forcing it to deform over bumps, the better the car will stick to the ground. Again, inconsequential on the dyno but proven on the track.

 

accelerating rotational mass is a function of the weight relative to it's radial position squared, so taking weight off the lower end of the radius (the aluminum hat) has much less of an impact, there is a lesser impact for the engine having to accelerate overall mass in general

however, reducing unsprung suspension weight has has advantages for people who have access to custom shock valving, etc.

the effect on power steering is inconsequential, not even worth discussing

 

Hay! you forgot about me! I was your first reply.

 

After a little debate, it looks like the vendor might make both 13" and 14" front 6-piston kits available.

Look for my red RX-8 at the Mazdatrix display out front at Sevenstock tomorrow!

There will be pieces on display, but no full kit available as of Sevenstock. Work on both front kits and the rear kit will continue next week.

 

Red 8?

I saw the Mazda Trix 8 in Blue that had the 14" kit on it.

Unfortunately it looks like it won't fit on Enkei 17" wheel.

We will have to wait and see.

Damn that 14" rotor is large. It felt very thick and heavy.


I'm sure the 6 puck slave and Rotor are more weight than my stock set up.

But that doesn't make any differance as that was only a display and not the real thing!

 

Okay, there are some issues with the kit, as presented at Sevenstock.

First, it is unlikely that we'll be able to use this caliper due to cost. The buy-in to have this caliper made in an RX-8-friendly size is north of $15k, and represents a volumne far larger than anyone I've met in the brake business is willing to handle. Basically, no one but me thinks they'll sell 25 sets world-wide.

Second, that 14" x 1.25" rotor is too heavy.

Dave at Mazdatrix is out-of-the-loop for a few weeks, and I'm the point man for further developments. Lucky me has all of the parts in his garage right now!

I have, however, learned of another vendor who is 99.5% done with a 4-piston 14" x 1.10" front brake kit using Wilwood components. He's done this for far longer than I've been working with cars, so his ideas are good. He also believes that his kit will fit inside the stock 18" wheels. He will also be producing a heavy-duty race application with a smaller 13.3" rotor and forged 4-piston calipers which is meant for 17" wheels. It's highly likely, when Dave's attention returns to this, that he'll evaluate and retail this kit instead of developing his own. There's simply no sense in reinventing the wheel.

However, the cost of the calipers in this kit is slightly higher for the purchaser because they're sealed and dust-booted, which is not a bad idea in my estimation.

It's likely that I'll be using a version of this kit on my car at SEMA, but not certain at this point. I still wouldn't mind using the 13.06" x1.25" rotors I've got here, just because they save SOOOOOOOOO much weight! If this vendor and I can come together on brackets, there might be an in-between BBK which will fit 17" and 18" wheels, fit on an MX-5, and still fit behind stock wheels too.

My main concern with 14" rotors is that the leverage becomes too great for street tires to handle, which activates the anti-lock earlier, resulting in worse braking distances. Without testing though, that's just speculation. Some of that could be adjusted with pad compound, but then you're fighting against the advantages of going to a BBK in the first place.

Anyone have any bright ideas or thoughts?

 

Admittedly this has no bearing on the questions you just asked, but what's the status on rear calipers? To be honest that was the main thing that grabbed my interest in this thread, as Racing Brake's BBK seems to have the 4-pot front caliper segment covered pretty well...

 

In any kit...all I would like is the rotors, calipers, and MAYBE pads...if you can say slap on a set of Hawk's and just be done with it...

Everything else I have already and do not want to pay for again...

Interested +1...

 

Early ABS intervention comes from poor balance.

There is a company with a 328mm kit that fits 17s and a 355mm kit that fits 18s and has the ability to deliver caliper piston sizes in each kit that yield a result within a couple of percent of the stock system's torque at the axle.

I am a fan of these products and will be using their kit if I go with a BBK.

 

All;

I've been following this thread for some time as I have also spoken to Eric many months ago about a kit for the RX8. While Eric was working with someone on this my shop was also working towards the same final product. In fact, short of the final hose kits we have completed this project and produced not one, but two front kits.

The kicker here is that while I'm telling you about them I cannot pay to be a vendor and sell them...! Seems this board is in a transition and nobody is taking new business accounts. I'm happy to keep the money in my pocket however I'd rather share with you the full details and pricing of both kits!

I'm fully aware of the ups and down, ins and outs, of this proposed custom six pot caliper set up and while I could have contributed to the plan, neither I nor Eric, nor the other vendor who was involved were prepared to front about $15k on hopes that we might move these items. Eric has been a great inspiration but we know better in this business and don't wish to look at our profits in the last 3-4 sets sitting on the shelf.

Personally I've taken 14yrs of experience and selected parts that will be best suited to the requirements of the customer. With two different kits available both are targeted at a specific market where the needs are a bit different. Of course one of them clears the stock wheel very well as this is a must.

I've also looked and and will further review the rear. While I'd love to use a certain manufactures rear caliper (as I've done on other kits) it cannot be done with the current parking brake cable design. Replacement custom cables would be required and added to the basic kit cost would drive up a rear price beyond what most folks are willing to pay. *I know this as the current one is costly now with low sales. And does not need cables!

As soon as I can get the business issues resolved with the good folks here I hope to be sharing more specific news. Be patient.

 

ok......I'll be patient.

 

Ok I have a few months to wait.

 

I am going to try Todd's TCE Performance Products BBK in the next week. I also hope to run his rear BBK setup before SEMA too. If all goes well, it's likely that Mazdatrix will also retail Todd's package.

$15k for 6-piston calipers was just too steep of a buy-in, as Todd said, and there are substantial benefits to using the 4-piston version of the same caliper. In truth, the mounts are identical on the two calipers, and in the future, should Wilwood decide to make this change themselves, converting from the 4-piston to the 6-pistion caliper will be a small matter of two nuts and one brake line on each side!

I had a chance to look at Todd's "hardcore race kit" too, and by the numbers, it's fantastic. More than what most anyone wil ever need on the street though, and more than what most of us could ever use on the track.

BTW-for those who don't know this Todd has 4 Pike's Peak class wins. This man really does know his stuff about brakes! I was very impressed in talking with him.

 

Installed, done, no problems and on his way home as you read this. Hopefully Eric can get you some pics shortly. Rear kit in due time.

 

Interesting story....We just had our nationals last weekend. One of the attendees had a local manufacturer of GM/Ford BBK's do up a 6 pot front kit for the 8.

His initial thoughts when he had them installed the Thursday before was that the pedal felt soft. Experience on the track that weekend led him to have them removed and replaced with OEM calipers which ended up being 100% on the new kit.

Moral I think is that just about anyone can do a kit for a car, but the kit needs to be tuned to the car they are going on.

I dont know what the exact issue was but I suspect it has to do with changing the amount of pressure required. If anyone can chime in with ideas I would appreciate knowing.

Cheers

Andrew

 

Yes you are correct in part- the issue is proper area.

This has an impact on travel, responsiveness, modulation and of course; bias or balance. I'm compelled to say however that if the "local builder" doesn't know or understand this I'd find a new builder....Sadly too many such kits are scabbed together and then the caliper manufacture is faulted when that's not the case at all. (I fought this at length on the WRX so I know it well)

 

Thats pretty much what I figured.

btw, those people looking for info on this kit can do a google on "tce rx8 brake" (without the quotes) http://www.google.com.au/search?hl=en&q=tce+rx8+brake

 

The lower the rational unsprung mass the better. You don't even really need gigantic brakes. Brakes decelerate the wheels, when there is less mass to stop, it will stop earlier. I say take as much unsprung mass off as possible, results in better acceleration, better steering response, better breaking, better handling.