BBK brake piston sizes - technical question

[kuni]

Guys,

I've been looking at a lot of BBKs and wanted to get the experts' opinions on the topic of piston sizes and how they affect braking/pedal feel.

Limiting the discussion to 4-piston calipers - it seems like the 36/40mm piston sizes are most common and popular for our cars. Stoptech and Brembo GT/Lotus uses these piston sizes in their calipers. (Please correct me if I'm wrong!) As a side note, I know the Spoon monoblocks also use 36/40mm pistons.

My main question is in regards to the F40 and F50 calipers that I've seen some people using on their NSX. These calipers have piston diameters of 38/44mm and 40/44mm respectively. I've heard a lot of people say that these larger pistons are too big for the OEM NSX master cylinder and this results in a softer/mushier pedal feel.

Does this mean the F40/F50 calipers are still more effective than the 36/40mm piston calipers, but just require more force on the brake pedals? I imagine there's some benefit to the F40/F50 calipers over the standard ones, but would love to hear some input from others who have tried this setup or considered them.

Thanks!

 

[Shooze]

You are correct in that the different piston sizing will not match up to the master cylinder bore. As a consequence, you will more than likely change the front to rear bias, pedal travel will increase and feel spongy and it could significantly affect the operation of your ABS.

In closing, Brembo and StopTech both supply OEM car manufacturers. And, with all the time and experience they have in supplying the aftermarket, I would go with the set ups that they have researched, engineered and suggested for the car. IMHO, you will be much better off and happier.

 

[stuntman]

The F50/Lotus package has a very good bias to it (much better than lotus/lotus), and does not cause a long pedal.

We ran it on the FXMD Time Attack NSX before switching to the Performance Friction NSX-specific 14" rotor package.


0.02

 

[kuni]

Thanks for the input guys - and very interesting to know that the F50/Lotus setup doesn't have pedal feel issues.

 

[stuntman]

Thanks for the input guys - and very interesting to know that the F50/Lotus setup doesn't have pedal feel issues.

It was a great package with proper piston sizes but those calipers are old technology and are heavy.

 

[f1racr]

Slightly off topic, but hoping Billy might have an answer.

I have some F40/F50 calipers and just wondering what Billy would suggest for brake pads ??

Even though car is track only car, I don't expect it to be a 20-30 lap full time racer, but more like a trackday style car.....

I was looking at the Performance Friction 7780.01.18.44 Race ready pads, but was a bit worried that I would struggle to get them to a nice working temperature range without going 100% for some laps...... ?? Any experience you can unload on me ??

Sorry to hijack the thread Kuni, but I thought it was kinda related.

 

[stuntman]

Slightly off topic, but hoping Billy might have an answer.

I have some F40/F50 calipers and just wondering what Billy would suggest for brake pads ??

Even though car is track only car, I don't expect it to be a 20-30 lap full time racer, but more like a trackday style car.....

I was looking at the Performance Friction 7780.01.18.44 Race ready pads, but was a bit worried that I would struggle to get them to a nice working temperature range without going 100% for some laps...... ?? Any experience you can unload on me ??

Sorry to hijack the thread Kuni, but I thought it was kinda related.

One of my favorite pads. Ryneen uses them too. They will be fine and get up to temp quickly. The concern for all race pads needing a big warmup is over exaggerated.

 

[f1racr]

Awesome, thanks Billy.

 

[CB72]

I'm using Porsche 993 turbo calipers upfront that are the equivalent I believe to the F40's.
After trying many types of pad material, I settled for Pagid "yellow" pads.
They work very well both on the track and on the road.
Don't forget to upgrade your rear calipers at the same time as the front to keep the appropriate bias ( around 60% upfront) .
Failing to do so will lead to a great disappointment:redface:

 

[RYU]

I'm using Porsche 993 turbo calipers upfront that are the equivalent I believe to the F40's.
After trying many types of pad material, I settled for Pagid "yellow" pads.
They work very well both on the track and on the road.
Don't forget to upgrade your rear calipers at the same time as the front to keep the appropriate bias ( around 60% upfront) .
Failing to do so will lead to a great disappointment:redface:

Nice setup. Mind if I ask which rotor/hat combination you're using?

 

[CB72]

Nice setup. Mind if I ask which rotor/hat combination you're using? 28, 30, or 32mm? I haven't seen a rotor with that much radial surface area.

The rotors are pure 993 turbo measuring 322*32 mm.
The hats are specific to take the Porsche rotors.
The system was sold by Movi't from Germany but I had to devise my own kit for the rear...

 

[puma]

The rotors are pure 993 turbo measuring 322*32 mm.
The hats are specific to take the Porsche rotors.
The system was sold by Movi't from Germany but I had to devise my own kit for the rear...

So you took a set of floating rotors for the 993 and changed the hats?

Do you have a pic of the bracket you used to install the caliper?

 

[CB72]

I didn't do it myself.
It was part of a BBK kit sold by Mov'it from germany a couple of years ago.
The 993 disks are non-floating.
After 5 or 6 track outings I change the disks by keeping the NSX specific hat.
Sorry I don't have a picture handy of the caliper brackets but the design follows the typical BBK kit layouts such as those from AP Racing or Stoptech.
Be aware that this kit requires wheels with an ET of 33 mm to accomodate the 32 mm disks.
I use CN 28s with an added 5 mm spacer...
The good news is that the stopping power is superb and you can modulate the breaking on the verge of locking the wheels easily.
It's compulsory to use a high boiling point fluid.
I use Motul RF 600.