hey all,
i'm looking to buy a BBK for my 1990 Miata. The car will be making around 250whp with a 1.6 turbo set up and will see around 6-10 track events with four 30-45 minute sessions a year, plus occasional autox events, and weekend canyon and mountain driving. it'll remain a nice-weather street car as well, and not a dedicated track or race-only car. Based on my research and needs and wants, I have decided to go with a StopTech STR-42 front set up on 11.75" rotors. As for the rear, I would like to retain the parking brake while still upgrading to a BBK kit if possible. I have a few questions I was hoping someone could help answer or guide me with before I make any purchases.

- For the rear BBK, I would like to retain the parking brake as long as it serves some sort of purpose. I know StopTech STR-21 rear caliper does not offer a parking brake solution, but the Wilwood 4 piston Powerlite rear kits from FM and V8R do. Knowing the front STR-42 kit has 36/38mm pistons made to balance with the OE sport rear caliper (which is 34.925mm I believe), and with the StopTech STR-21 rear caliper (which is 36mm), would it be adequate to match the front STR-42 kit with the Wilwood 4 piston Powerlite caliper that retains a parking brake, since it is a 35.052mm size? Would this mix-and-match of kits work properly/make sense in terms of piston size/brake balance/pads available? Would a proportioning valve help in making any mix and match setup work, regardless of piston size discrepancies? I will be using a 1" Wilwood master cylinder unless there is a better suggestion.

- I am aware the parking brake on the Powerlites is not as powerful as the stock parking brake, but am looking for someone to shed light on just how much weaker it is. Would it be able to hold the car on, say, a 5-15 degree slope, similar to the one you would find at a gas station parking lot or apartment complex parking lot/driveway? If It cannot hold the car on a moderate slope like your average driveway or parking lot, I will likely skip the Powerlite setup and go for the STR-21 rear kit.

To reiterate, I am set on the STR-42 11.75" front set up, but would like some guidance on the rear kit in terms of mix-and-match capabilities between front STR-42 and rear Wilwood Powerlite, and how weak the parking brake on that Powerlite caliper actually is.

Please feel free to give any other feedback or suggestions you might feel are relevant in regards to my questions and goals, appreciate the help

 

Subbed for any feedback...

 

reached out to V8R and GWR also with this question .. the consensus is that the parking brake on any rear bbk - including the mentioned Powerlite - is useless at holding the car in any kind of slope, and is only designed for race classes that require a car to have a parking brake, regardless if it’s actually useful or not. GWR also noted that the powerlite caliper is a downgrade in terms of pad size and overall has no real advantages compared to the OE rear caliper. Best performing set up with parking brake is ST(R)-42 up front, with factory sport caliper/rotor in the rear. Also reached out to FM, have yet to hear from them but i assume they will say the same. i’ll probably go with str front and rear, and wave goodbye to the parking brake. or carry a block of wood in the trunk lol

 

I have the Powerlite rear setup on our track NA. I would not recommend it for the street. Holding power is pretty minimal... it usually won't hold on my slightly sloped driveway. It's barely adequate for torqueing lug nuts on level ground.

I have the 11.75 fronts with Dynapro radial mounts, a Wilwood 1" master and original 1.6 booster. Braking feel is FANTASTIC. Pad changes take less time than it takes to get the wheels off, and you will want to change pads from street to track. I know the Stoptech are the new hotness, but the Wilwood combo works really well.

 

I know you said you're set on the STR-42 front, but the BX1175 is on sale for black friday... If it fits your wheels, it's the most brake for the money. https://supermiata.com/Supermiata-bx...brake-kit.aspx

Otherwise, just echoing others that there's little point in going rear BBK.

 

I'm running a dual duty turbo NA . I pieced together my front 11" Wilwood based on the Dynapro calipers. In the rear I maintained the OE caliper with the NB1 bracket and rotor. More then enough braking for what you want to do. The 11" Super Miata kit is a very good option. When I did mine it was not available.

 

If you need a parking brake, get the brackets to run stock calipers with sport brake sized rotors. If you want to waste money, put a hydraulic e-brake into the rear circuit that has a latching mechanism and use the STR-21's, but then you run the risk of the pressure bleeding off over extended periods of time then the car will just randomly start moving.

If you don't need a parking brake, feel free to go to the STR-21 rear setup. It looks great and drops a decent amount of unsprung weight but realistically the stock rear sport brakes can hold their own.

Piston sizes indicate you could mix and match but the parking brake on those Wilwoods is absolute garbage.

 

appreciate the feedback from those with sport and powerlite rears. I'm aware the sport rears can hold more than their own with my power goals and above, but my train of thought is to always overbuild when doing important supporting mods for power (never hurts to have too much brake as long as its properly balanced). Partially because I know this car will only become more and more powerful in its life, and it's nice to know if I go with ST front and rears, I'll basically be one and done forever in terms of brake mods (plus saves me the $$ from doing sport rear upgrade now, then far down the line having to change that set up again). Also because I'm a man of bling and street cred yo when it comes to nice performance mods, and the rear STRs simply look miles better than stock sport rears, and it comes with the unsprung weight and consumables cost savings, and simpler pad changes, which are good enough selling points for me. I ran a sticking left rear caliper for close to a year that prevented me from using the handbrake at all, so at least I know what I'm getting into. @turbofan , unfortunately that kit was sold out by the time I checked the link.

anyway, the whole brake upgrade plan was put on the backburner for now thanks to some really good black friday deals that popped up, meaning my turbo build has officially (kinda?) started

 

in the meantime, check out my fully restored thread here. it'll very soon turn into a fully restored turbo build thread, since that's where the real boys party. it'll also give a bit of insight as to why I like to ball out on fancy parts (emotional connection to the car, blah blah)