I couldn't find it in the thread, but can someone list the leading and trailing piston diameters for the RB fronts?
Thanks, Heath

 

Gee, you couldn't find it somewhere in the 1500 posts?

sure, i can help you....

the front RB pistons are 38 and 36 MM dia.

that makes overall piston area (front) 6.66 sq inches V stock at 6.335

the stock FD longitudinal total brake effort is 68% front 32% rear

the RB balance (w the larger rear rotor) is close at 70% 30%

just a front AP caliper w a 13 inch rotor results in a 74% 26% (im)balance

i continue to love my RB setup.

please do keep in mind that FD uprated brake performance turns on a larger more efficient front rotor mass and more rotor leverage in the rear and a longitudinal balance between piston area. there is actually not much wrong w the FD front caliper, just the rotor mass.


howard

 

Thanks Howard! Is the 68% front 32% rear under max line pressure? (just wondering at what point that is measured as the proportioning valve changes bias depending on line pressure). Since it's not a static value, I've been looking for a prop valve graph but so far nada.

 

Ah also, does anyone know the pad height and width for the fronts? I cant find a pad diagram for it... I'm most interested to know the height of the pad itself (no backing plate). Trying to do a few calculations here.

 

fsm, p-19.

 

So are the DTC-70s still the one to have for a serious track fd? I have f&r racing brake bbk and stock master cylinder. My ET700s are fading and feel very mushy with long pedal and bad initial bite.

 

The DTC 70's are great. Warm up quickly. I can get multiple events on heavy braking tracks at 400 RWHP. Buy with confidence, but make sure you rotate pads inside to out each event at there is heavy taper due to caliper flex. Run at least ATE if not Motul/AP fluid too as the calipers get hot.

-ch

 

Sounds good. I also probably need to change the ATE as it is a few years old. I'm at about 2830lbs with me in it and 315 rwhp.

I've heard some people say that DTC-70 has too much initial bite? Maybe this was a different car though.

 

Pedal feel is a pretty personal thing. For my style, initial bite is a good thing, but YMMV. It's one of the things I like about the DTC compounds...you might get a chirp if you're too aggressive but ABS makes that a non-event and it has the advantage of getting your weight transfer done so you can get on to threshold braking.

At 120 MPH you're covering about 180 feet per second. For my money, I want to load that front axle quickly so I can take full advantage of big brakes and sticky tires.

-ch

 

Ah yes, good point. I think that I will try the 70's because I have the stock master, if I had a 929 I might try the 60's. But I'd like to remove the ABS and go to dual masters soon, the car is becoming track only.

 

Oh one thing to note, I can't find the DTC-70 for the stock rear caliper (RB BBK). Is it ok to run the front with DTC-70 and rear with DTC-60? Or will this mess up the bias? Thanks

 

Yep, DTC-70 front and DTC-60 is the "safest" setup.

BTW: this is what I'm running.

:-) neil

 

Ah I see, so will the fronts tend to lock before the rear given the more immediate torque? And this is more stable or safe?

 

It is always more safe & stable to have front tires lock up before the rears on a short wheelbase car like the FD. Half of good braking is having properly matched tires to work with the brakes. Something to think about. It is perfectly normal to run a low to mid friction pad in the front, with a low friction control pad in the rear on the FD.

If you have extremely good brakes and your tires are crap, you will always lock under 90% to full pedal pressure. Nothing wrong with the brakes in that case, other parts of the car need to be modified.

 

using the RB big brake kit, will the stock brake cylinder work with the kit?

 

Yes, the pedal will have a bit longer of a throw, so try it out and if you don't like it you can go to the 929 master cylinder.

 

I'm resurrecting this thread because I'm looking for OE-size performance rotors and upon contacting Racing Brake they can offer a 4-wheel set for a great price but only if 10 or more sets are ordered...

So I decided to create a GB for these! OE size only, full floating, 2-pc, open slot. Hopefully we can get to 10 or more sets.

I got approval for the GB and it's here: https://www.rx7club.com/group-buy-center-69/gb-racing-brake-oem-size-2-piece-performance-rotors-1000219/

Anyone need new brakes??