I need to sovle a brake riddle - SCCA STL
 

I am changing from T4 to STL because the changes to the T4 rules have made STL a more attractive proposition plus the STL group seems to have a some good growth momentum.

So.. BRAKES!

We CANNOT upgrade front rotors! We can, however upgrade the caliper. The rules spec a maximum front rotor diameter of 300mm and since OEM are 292mm, I'm basically stuck with the OEM rotor size.

So I am looking for non-floating monoblock calipers that work on the OEM rotors. Must also clear 17" wheels.

*06-07 WRX calipers look like the easy button
PROS: bolt on, cheap, symmetrical piston size so orientation doesn't matter, no issues with bias
CONS: heavier than aluminum, limited race pad options, especially where SCCA contingency exists.

05-ish WRX STI calipers
PROS: light, inexpensive remans available, lots of pad options for racing.
CONS: Do they just bolt on? Have to swap sides to make bleeder upright but then pistons are oriented wrong, or don't swap sides but swap bleeder location.

Any other "bolt on" options that work with OEM rotor size that would be an upgrade over the oem floating caliper?

Forgive me as I'm not familiar with SCCA, just NASA, and this is tangental.

With NASA, factory optional brakes are considered stock in terms of points in ST/TT5. What this means is the BRZ/86/FRS can use OEM Brembos without taking a point hit.

1. Does SCCA require downsizing brakes for classing if they're larger than your specified numbers there?
2. At what point can a FRS be called a BRZ if they're picky enough that the FRS isn't a BRZ and can't use the BRZ optional brakes? Are the bumpers/badges enough?

I think you are onto something. It appears that the stock rotors are 272mm and the PP rotors are 292mm. If that's the case, switching the Performance Pack rotors and calipers should be on the table. Wouldn't that be the case since they are an option on the platform?

#1: Not sure because the STL class is for cars that are NA 2.0L and under and cars that fit that criteria generally don't have brake rotors >300mm but I suppose the ones that do would need to be compliant with the rules.

#2: AT ANY POINT! However, Subaru does NOT participate in any contingency programs so there is ZERO value in representing the brand (unless you have your own sponsorship). Toyota has contingency so in certain classes if you win, they pay $400 for each win and they also provide an amount of travel reimbursement for towing to Runoffs. So I'm fine to use ANY brakes so long as my rotor diameter doesn't exceed 300mm. The problem I find is that most other compatible calipers works so long as you put on a rotor that exceeds 300mm.

Only in other markets. North American cars all had 292mm rotors.

Stock brakes with the right pads are pretty good on these cars. If that isn't sufficient, run PP Brembos. AP Sprint is 299mm also.

PP Brembo’s would probably be your best bet. I would be afraid of the WRX calipers may mess up bias too much.

What braking issues are you having with the factory calipers?
Don't get me wrong. I run an Essex Endurance setup because I want to, but I'm also not subject to your restrictions.

Sounds good. Are they a direct bolt on and work on our 292mm rotors? Secondly, will they fit under a 17" RFP1?

The issue I have is that they are floating calipers. They are pretty good, sure, but now that I am in a class that allows me to not use "pretty good", I need to better optimize within my restrictions.

The Brembo setup is heavier than the cast iron setup by 2lbs, unsprung. If that doesn't matter, have at it. You will need the PP rotors. RPF1s are one of the most restrictive wheels available. I never understood their popularity.

Isn't the PP rotor larger than 300mm? So it looks like the WRX caliper may be front contention.


Why are RPF1 popular? Weight, price and availability. It's a nice flow form wheel, works great for air flow and maximized rule allowance (In T4 the rule was 17x7 with a minimum weight of 15lbs and the RPF1 fit that criteria perfectly, none others did at the price range). In STL we are still restricted to 17x7" wheel which is great for me since it means I don't need to buy 16 new wheels!

Rotors are 326mm, 316mm in the rear, but the fact that they're a factory option should keep you in class.
For that size, that's not all that light, but if it fits the class rules, I understand.
Good luck. I don't feel simply being a fixed caliper outweighs the cons of the Brembo package still being a commuter car brake setup. Especially the added weight. You're not really gaining anything other than the weight. Perhaps some more thermal mass, but you don't sounds like you're at the limit of the cast iron setup from a thermal mass standpoint.

Ok, so this won't work. Class has a hard ceiling of 300mm rotors.

Closest application I could find. $4k.

https://trialengineering.com/product...rz-toyota-gt86

"Front brake kit utilizing 4 piston forged monobloc caliper and fully floating rotor, designed specifically for use with 15" gravel wheels. Developed to provide the superior performance for Open Class and regional competition.

PFC ZR94 caliper's monobloc design increases stiffness for a firm, consistent pedal feel. The internal fluid crossover eliminating the risk of damage or failure compared to calipers with an external crossover pipe.

299x32mm rotors are the go-to dimension for gravel brakes from group N production cars to R5. They offer maximum braking power and heat dissipation within the space of a 15" rally wheel rim."

You basically have to use stock brakes. However, with the weight of the cars being low in STL, you'll be totally fine with just good pads and fluid.

C12 front C1 rear is a super popular combo for classes with this type of restriction; you won't run out of ceiling with this pad combo unless you're just blatently sitting on ABS at every braking zone.

In the NC Miata world there's a "little big brake kit" which is Wilwood calipers on stock rotors. Thinking about it, you only need caliper brackets and custom lines for such a setup. Perhaps there's a fabricator out there that could do the brackets? I realize these are brakes and the fabricator has to be skilled, but maybe some company that does brackets for other cars would be willing to make some for this platform? I'd expect getting custom lines wouldn't be too difficult, I know there are suppliers for those.

Confused here, if the only restriction is rotor size, AP sprint would work.

If more, then I would suggest the wrx Sumitomo calipers. Those are good and pads may be limited here, and would require to use japanese sourced ones.
Save 4lbs per corner

Note that while the WRX caliper is non-floating (fixed), it is not a monoblock caliper. The caliper consists of two halves that are bolted together. A monoblock caliper is machined out of a single piece.


Do you have a definitive source for that 4lb/corner delta? I've seen people quoting each other back and forth on the weight savings, but the actual measured weights I've seen suggest it's much much less of a difference than that.


https://www.ft86club.com/forums/showthread.php?t=44669
gives the weight of the stock front caliper+bracket+pads at 7.8+3.8+1.8 = 13.4lbs per wheel


https://forums.nasioc.com/forums/sho...5&postcount=12

gives the Sumitomo front calipers+pads at 24.5 lbs, or 12.25lbs per wheel.

These put the weight savings around 1.2lbs per front corner. Other measured values I've seen vary a little bit, but not enough to get to 3-4lbs/corner.

I haven't looked into the rear weights but it may be closer to the 3-4 lbs there given the rear calipers are aluminum. But between the need for an adapter bracket and the shift in brake balance, I haven't considered this option.

That is a good question, I saw in different discussions numbers thrown. Best way would be to get a GC8 caliper and weight, let me ask around and confirm.

I bet you're fun at parties.

Thanks to a GR forum piening2150 member, who had a GD Wrx caliper and pads at hand, now I have a confirmed weight.
GD Wrx Sumitomo Opposite piston Iron casting: 4.575 kg
Pads: 740g
Loaded caliper: 5.315 kg

Compared to OEM, which have the measured weight (loaded) of 6.342kg, we have about 1kg reduction (2.2 lbs) per corner, or 2kg (4.4lbs) per axle.


Hope this data helps folks here.

Just updating this thread for the outcome...

I have installed the ESSEX AP Racing kit with 299mm rotors. The supplied hat/rotor combo is great, however they are a bit too wide for STL rules. I will run these in other classes but when I run STL I will use a Wilwood rotor. I was able to source a Wilwood 8bolt Hat with a rotor that is a legal width. Because the wilwood rotor is narrower, I needed to utilized spacers behind the pads to take up that space.

On the rear of the car I installed the FHI WRX calipers with the KNS adapter - I did not weight these but they do feel lighter than the floating caliper that came off the car.

AP kit:
https://www.essexparts.com/essex-des...0299brzfrsgt86

Wilwood Hat: https://www.wilwood.com/Hats/HatProd?itemno=170-9206

Wilwood Rotor: https://www.wilwood.com/Rotors/Rotor...emno=160-15877

Spacer: https://allstarperformance.com/calip...hick-all42042/

Weights: (according to my bathroom scale!).
Oem rotor: 17.2 lbs
Oem caliper: 12lbs
AP rotor: 12.6 lbs
AP caliper: 4.8
Wilwood rotor: 8.2 lbs

OEM caliper+rotor = 29.2
AP Caliper + Wilwood hat/rotor = 13
Weight saving per corner: 16.2 or 32.4lbs total off the front end


Edit: My ESSEX rotors may be for sale. Just the rotor, not the hat. https://www.essexparts.com/ap-racing...nd-60-vane6603

These retail for $299/ea, meanwhile the Wilwood equivalent is $75/rotor so it makes sense for me to sell these to someone who wants them and swap to the Wilwood rings. If you have the AP kit and need to replace your rotors/rings - ping me, I'll make you a deal.