Vtbandit has a set for sale in the classifieds

That could be an option.

mx5-kiwi my two cents.
I sold my sport rear kit (sport calipers and rotors) because i didn´t lock rear brakes (as you).
I´m planning to mount Wilwood 11" vane rotors with Wilwood calipers and MC4 for parking brake. It will fit over 15" at the limit.
Rear proportion valve and dual master cylinder (booster deleted) with remote brake bias to fine tunning.

That´s best rear brakes you can get to mix with 11.75" Superlite TSE at front.

There is no justification for a rear vented rotor in these cars, IMO. No need for that much heat dissipation. The stock 10.9" Sport rotor does a perfectly adequate job and weighs far, far less than any 20mm vented rotor.

I ran 11" vented rear rotors a couple seasons back with IR temp sensors. Rotor temps were too low. Way overkill - unnecessary rotational mass that you just don't need. I later switched to a non-vented sport size rear rotor and all further temperature monitoring has shown they're right in the happy operational window (a bit on the low side of it, if anything).

Huge thanks to AA-Ron for helping me source a used set of Sport rears. Now just need to (hopefully) change my order of 1600 rear G-locs to sport, fingers crossed with 949 :)

and ship the whole lot here.

Opinion on r12 versus r14 rear compound with 225 NT01 and Z214 mediums....with the superlite front R18 and no bias adjuster?

My :2cents: I would run R18/R14 if I had your pw/wt.

I am currently running R10 rears and my next set will go up to R12s in the rear.

FYI - Comment from 949 is that the R14 is an endurance pad and not of the same family as the R8 -12 and that it would be best, in this situation at least, to stick to R12 with th R18 front.

What calipers are you running? Sport calipers are not the same that a powerful Wilwood one. Of course brake bias is also a setup to take in consideration.

We need a facepalm emoji.

The only thing that matters in this regard is piston size, and more is not necessarily better. Assuming you have sufficient front torque, choice in the rear all comes down to balance.. Most 11.75" front kits use calipers with piston area in the range of 3.0-3.5 in^2. To balance with that in the rear, on a ~11" rotor, a caliper with piston area of 1.2-1.6 in^2 can work, with the ideal combo for each car coming down to lots of variables like weight balance, aero balance, tires, setup, etc. More piston area beyond that in the rear just adds more rear braking torque which creates an imbalance with the front that you can't fix without increasing front piston area accordingly (Speaking from direct experience here, we've had custom Wilwood calipers made to experiment with this). That's a slippery slope into having to re-do the rest of your brake system from the ground up; dramatically increase the piston sizes in all the calipers and you'll need to change master cylinder size, pedal ratio, etc. which is exactly why most front BBKs match the piston size in their aftermarket calipers at least pretty closely to the factory piston sizes, and thus why the piston sizes in the rear calipers need to also remain fairly close to factory specs. Now, if you couldn't get enough braking torque with the piston and rotor sizes discussed here, then you'd have a good reason to go down that road... but in fact the rotor and piston sizes discussed here with pads of the right friction level can supply sufficient braking torque for a Miata of typical race weight on race tires with significant downforce. So then, Wilwood, OE, or any other brand of rear caliper is inconsequential - you need the piston size you need to maintain balance, and so the only deciding factor between a vented or non-vented rear rotor comes down to how much heat you're putting in that rear rotor. Aaaaand we come back to what's already been pointed out; that you won't put enough heat into the rear rotor to justify the added mass of a vented rotor.

Thanks to clarify this mess.
So 120-13517 Powerlite with integrated handbrake (1.58 sq area) over 10.9" sport rotors should be best "allinone" rear kit to mix with Superlite TSE... What´s sq area for oem sport rear brake and non sport rear break?

The Powerlite is indeed just about the only Wilwood caliper with a piston size suitable for the rear of a Miata. That said, it's not an amazing caliper and the parking brake is virtually useless - it exists mostly to satisfy rules for certain race series that require that you retain a parking brake but don't regulate how effective it is. The stand-alone MC4 idea would be a lot more functional, but also obviously a lot more involved in mounting a second caliper than an all-in-one... and add up the weight of a Powerlite (which is one of the lightest calipers) plus the MC4, plus the large bracket needed to adapt both calipers to the car and you end up not far off (if not the same as) a factory rear caliper.

Piston diameters for non-Sport rear: 1.25" and Sport rear: 1.375". You can calculate piston area from there, it's a good thing to learn how to do if you want to start blazing a trail beyond just picking a kit that a company has already done the development on. You can find the equation to calculate caliper piston area with a quick google search. Pay close attention to number of pistons in a sliding factory-type caliper vs a fixed position multi-piston caliper and how that affects the equation.

Great posts Ryan!

In addition to all Ryan said keep in mind the faster you go often the less rear you need. Especially when combined with sticky tires. Pay attention to pad torque ramp rates. Some pads are more ideal on one axle vs the other. I like a flat rate on the rear and rising rate on the front. If you get your hydraulics wrong and get forced into a pad for torque only reasons you may fight bias issues. The rear brakes are most effective during initial application. As weight transfers less grip is available so you want to decrease torque as this occurs. Then as the car settles how a pad releases is important for trail braking. The right pad can help or hurt you here. Rear rotor temp is often overlooked. If outside ideal operating temps operation become unpredictable. Most choose larger rear rotors for additional torque. In some cases a sport caliper on smaller factory rotor would be best. Nothing needs rear vented that I have seen.

Great
 

Thanks for your post, very useful. I have to check calculations in the web.
Anyway i have right now a dual master cylinder (.625" bore front and .7" bore rear) without booster and superlite tse at front. Still thinking about election brake pads so your last post is a great help to take the right one.
About rear calipers.... I don't like so much powerlite because handbrake add is useless, it carries small and thin brake pads... In the other way around D501 has a just a little more sq, bigger brake pads.. The only problem is that it needs vented rotors because Willwood hasn't a solid rotor solution with minimum thickness require.

To reiterate: If you put vented rotors on the back of your Miata, you are doing it wrong

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I think V8R has dual piece solid rotors.
Those rotors/hats should be a solution to use D501.

Is this still in the pipeline?

Yes. Just finishing up our 11" ND rotor Wilwood Dynalite kit for the NA/NB using our patented Boxmount tech for production. The 11.75 x1.25" floating rotor 4 piston Superlite radial kit will follow. No ETA though, sorry.
That CAD drawing (not ours) you linked to in the other thread.. the duct will hit the shock at full lock. We know because or 11" and 11.75" kits both have integrated 3" ducts ;)

Thanks for the info. I’m guessing the 1 inch rotor is going to be a proprietary one? The box mount should be a real improvement, the amount of flex in a standard lug to lug adaptor there is truly worrying. Probably not the kit for me though since I need brakes now. I’ve basically parked the car until this is sorted.

The CAD was mine, using Alec’s scanned upright. Just a quick bit of CAD to 3D print some test calipers and see what could fit. I had a 6UL professionally scanned today so hopefully can skip a few prints. A caliper is roughly a full 24 hour print! Thanks for the hint on the duct, I thought it odd no one had done that before.

We will start a new thread on our Boxmount stuff when the time comes. More details then.