zli944

In general, Miata guys get the RX8 calipers as an upgrade but I'm trying to understand general brake theory to see if it's viable to put a NC BBK in a S2 RX8. This is on a daily car so a pedal box is not viable. I'm also not married to putting this kit on the car, just curious if it was possible since I already own the thing.

Overall hardware is the same between the NC and RX8, it's a common upgrade for NC guys to go to the RX8 rear calipers or even on all 4 corners. The rotor diameter is the same as well on the BBK. So I'm not worried about overall fitment, it should bolt in, what I am concerned about is going to be overall pedal feel and safety. I've read that mismatched calipers can often lead to mushy brake feel, long pedal travel and general lack in performance.

From a cursory search, it seems like the brake systems are pretty comparable and I shouldn't have too many issues.

Brake Master Cylinder (BMC):
From what I gather, part of what makes BBKs car specific is the piston to BMC ratio.
Miata NC BMC Bore Size: 7/8"
2010 RX8 S2 BMC Bore Size: NOT SURE, I've read both 7/8" and 7/8" + 1mm

Booster and boost ratio:
Honestly no idea what the actual numbers are but I'm also not sure if this is taken into account when doing BBK R&D

Given that there are so many factors not listed in play here, I may just throw the kit in and see at least how the pedal feels.

Loki

iTrader: (1)

The stock brakes on this car are very good, especially with brake pads appropriate for your needs. Also the NC BBKs I'm seeing are barely bigger than a stock RX8 front rotor (12.7" vs BBK 12.88"). Depending on which kit you're getting, it's almost guaranteed to have more piston area than the stock ones (by virtue of having more pistons), so maybe this will help figure out where you land and whether its worth the squeeze: https://www.joesracing.com/master-cylinder-math/

zli944

The kit came WITH the car, which is the only reason I'm considering it.

Fair point on whether or not its necessarily an improvement, but I would like to maximize seat time when I do track the car having experienced some pucker factor brake fade late in some sessions on the FD running just plain rotors and carbotechs front and rear.
I'm absolutely fine with losing some laptime if I get to stay out longer while retaining confidence in the brakes. Though from my recent experiences, the limiting factor may still be engine heat. Maybe i should've bought a miata...

Unaffiliated plug but Turn8 runs track days with 45 min to sometimes 1 hour, 1.5 hour open pit sessions on top of the usual 3-4 20 min sessions. Don't think many other orgs have that setup.

Loki

iTrader: (1)

Which track are you running? And which Carbotech compound?
I would start with the stock set up and good pads fir for the speeds/braking zones (Hawk DTC60 have been great in all my outings, and cheaper than Carbotech) and go from there. Of all the things on this car, the stock brakes have never let me down, the only reason I have a BBK is because it was basically free and I stopped racing.

As for engine heat, depending on what you're experiencing there may be simple solutions. If you're going to race any RX8 with its original radiator, I'd look closely at replacing it anyway. That plastic is 10 years old at best.

zli944

@Loki I was running XP8s front and rear on my FD and on Thill East, West and once at Buttonwillow. The 8 will most likely also be running these tracks, hitting Laguna later in Oct and hopefully I can hit Sonoma and Willows as well eventually.

I did like the Carbotechs but they wore fairly quickly, might give the DTC 60s a shot if the NC BBK feels awful. The kit also came with front pads but I had already picked up G-LOC R8s for the rears.

I plugged in some numbers based on the links you sent me and the kit should run fairly similar ratios to what you would find on the NC, so in theory, It should feel similarly.

I have the 48mm koyo and some foam I'm hoping resolves at least some of my heating woes but we will see.

speed7

Personally in the past I had a few pucker moments with my FD. But I never tracked it… now fast forward 15 years later.. on the track I’ve boiled my fluid at Spring Mountain Motorsports Ranch, I’ve been 4 off, 2 feet in, at streets.. and I still feel way more comfortable in my Rx8 than I ever did in my FD. You have to push the brakes really hard in this car to cook them when running a track compound. And the 4 off I did at streets was a stiffness setting too high, which I had to do a think on but fixed at the next session. I wouldn’t overthink the brakes too much on the Rx8. Race section has info on pads, I use ST43’s and love them. Not for the street though. And oem rotors. In the past when I did street the car I just used oem pads and rotors. Would swap everything in back for a track day. This was pads and rotors.

and on your radiator comment, I personally use the Ron Davis Racing competition radiator. Part number 1-30RX08.

TeamRX8

iTrader: (25)

again, you don't really share the appropriate information from the beginning, such as the comment above or that you intend to track the car as mentioned after this

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