The Ultimate ABS Solution for the NSX

[Honcho]

The 91 NSX was over-biased to the front, which is why they added much more brake to the rears for 97+. No one really knows why, but best guess is that is what their test drivers (Senna, Rahal and Nakajima) preferred. Most open wheel racers prefer a loose car since it rotates easier, but for us mere mortals it means a car that spins. A lot of car industry reviewers crashed the 91 NSX after losing the rear end, including famously Car & Driver in their first test of the car.

As John mentioned, the 97+ rear caliper is a great way to go.

 

[RYU]

The ultimate ABS indeed!

I've ran several brake packages off-the-shelf and custom from the RYU garage (lol). I currently run the RFY rear oversize kit which is a BIOT special order I believe. After running at least half a dozen BBK setups I settled on a ST40 front with the stock NA2 (or NA1 is a little better) oversize kit. I've also ran 3 different E-Brake setups. Stock setup still works the best in this regard.
LMK if I can help. @GUNDAN323 has experience with custom kits as well. Maybe he's willing to post his awesome spreadsheet on brake bias with various caliper/rotor combinations.

 

[RYU]

If you're running the NA1 rear calipers still with the larger rotors then upgrading to NA2 rear calipers will probably get the bias much closer to ideal, they use a much larger piston and still have an integrated hand brake.

They can be tough to find though, if you keep an eye on rockauto you can occasionally pick up a set for $500ish.

I'll just provide my experience here for folks...

If @MotorMouth93 is referring to using the larger NA1 caliper with the larger *NA2* rotors and caliper brackets then yes... great combo. However, if John is referring to NA2 being better than NA1 using an upgrade kit like the BIOT I have to strongly recommend using the NA1 caliper bracket for this. It's just less cumbersome given clearances with the BIOT caliper adapter bracket. I'm only referring to the bracket here... not the caliper itself. I believe the NA1 and NA2 calipers are interchangeable with the different brackets.

This is the RFY/Biot rear oversize setup i'm referring to. You can see the pad sweep area isn't exactly optimal but the setup has worked quite well for me. It's really really nice having the stock e-brake for what is mostly a street car now.

 

[MotorMouth93]

I'm referring to the NA2 caliper itself. @blaketjones has an oversized rear setup already similar to the one you have @RYU, so I believe he can keep his oversize rotors, keep the adapter bracket and NA1 bracket, then just bolt the NA2 caliper onto the NA1 bracket/adapter setup and get the larger rear piston.

 

[Honcho]

@RYU I love seeing those blue JRZ peeking out.

 

[stuntman]

s

The 91 NSX was over-biased to the front, which is why they added much more brake to the rears for 97+. No one really knows why, but best guess is that is what their test drivers (Senna, Rahal and Nakajima) preferred. Most open wheel racers prefer a loose car since it rotates easier, but for us mere mortals it means a car that spins. A lot of car industry reviewers crashed the 91 NSX after losing the rear end, including famously Car & Driver in their first test of the car.

As John mentioned, the 97+ rear caliper is a great way to go.

If he puts a 97+ rear caliper (48mm) on his current setup, his brake bias will go from a front-heavy bias of 62.1% down to a 55.7%. I need to go back through all of my notes because I think the 97+ NSX has a proportioning valve that brings its static 52.2% up to 60% front bias.

More front bias causes the front brakes to lock up first, and more braking stability, not the opposite. I will update this thread when I have time to go back through all of my notes an calculations to verify the NA2 97+ brake setup is at 60% with the proportioning valve. If so, going with the 97+ rear caliper might be worse than sticking with his current setup.

 

[Honcho]

s

If he puts a 97+ rear caliper (48mm) on his current setup, his brake bias will go from a front-heavy bias of 62.1% down to a 55.7%. I need to go back through all of my notes because I think the 97+ NSX has a proportioning valve that brings its static 52.2% up to 60% front bias.

More front bias causes the front brakes to lock up first, and more braking stability, not the opposite. I will update this thread when I have time to go back through all of my notes an calculations to verify the NA2 97+ brake setup is at 60% with the proportioning valve. If so, going with the 97+ rear caliper might be worse than sticking with his current setup.

Makes total sense. I was thinking about it from a weight transfer standpoint. Having the fronts grab really hard versus the rears throws the weight forward and unloads the rear tires, but it's probably irrelevant if your rear tires are already sliding!

 

[MotorMouth93]

Maybe I misunderstood but I thought he wanted to move the static bias rearwards, hence "larger rear calipers"?

 

[mhawke_2]

Is consideration being given to supplying a kit without the Bosch brake module if we can supply our own?

 

[blaketjones]

Is consideration being given to supplying a kit without the Bosch brake module if we can supply our own?

That would be a discussion with 909 Motorsport. I’m sure it’s possible, you’d just need to work through the other parts required (sensors, switches etc.) assuming you don’t also have those since you’ve mentioned ‘module’ and not system/kit.

 

[NessexFurrball]

This is very interesting. Awesome work!

 

[Valhalla]

Very exciting stuff. I was talking with our local club racers with NASA and they all raved about the Bosch system. Following this thread closely, but that price point.......

 

[bsansx]

Looking forward to the final results and price for my 1993.

 

[gesundlich]

Any updates?