jimlab

Actually, the discussion got started with a comment about 6-piston calipers stopping "better" than 4-piston calipers.

With the exception of RZ-spec fronts, of course, but they're certainly better than nothing, and some of us aren't willing to lose our parking brake functionality.

Your 13.0" front rotors are about 12% larger than the stock 11.6" rotors. In the rear, your 12.2" Precision Brakes rotors are about 5% larger than stock, so that's a ~7% imbalance, give or take. If you increased the rear rotor diameter to 13.0" also and moved the caliper a corresponding amount, you'd probably have a pretty good match for a front kit. Not perfect, but pretty damn good. Maybe someone should make a bracket.

Still, it's better to have less rear brake bias than it is to have too much rear brake bias.

neit_jnf

iTrader: (17)

I'm surprised my comment above started this great discussion

I'm Puertorrican btw...

rx7dv8

Grind down the "Approved in Japan" and repaint them....then they'll look great

maxcooper

Don't forget about the pistons! Both my front and rear calipers have different piston sizes from stock (I included the RZ sizes, too, which have the same area as 93-95, but the fronts have differential bore pistons):

FRONT:
stock = 1.42" + 1.42" pistons = 3.17 square inches
RZ = 1.33" + 1.5" pistons = 3.17 square inches
AP 4-pot = 1.5" + 1.63" pistons = 3.84 square inches (+21%)

REAR:
stock, RZ = 1.37" piston = 1.48 square inches
Wilwood NDL = 1.12" + 1.12" pistons = 1.97 square inches (+33%)

(Note that you only count one side, or half the total area, for calipers that have pistons on both sides. You count the full area for calipers that only have pistons on one side, like the Mazda rear calipers.)

So, I don't have any specific calculations, but I have a larger piston area increase over stock in the rear, and I suppose that helps to balance out the larger rotor diameter increase in front.

Very true. But I can tell you that way-too-much front bias feels like crap.

-Max

jimlab

???

He was referring to the original poster, ccw998.

jimlab

Agreed. I don't think anyone should upgrade only the front brakes and do nothing about the rear, but I do think the '99-spec rears are a good substitute for a 4-piston caliper with no parking brake option.

RX794

I know we're talking about the 929 master cylinder here. I think Fujita Engineering(FEED) may offer the same thing with an adapted brake line, here's a pic of it:


I can't read Japanese, so I couldn't get any info on it, can someone check to see what it reads and let us know?
Here's the link to the website with the info:
http://www.pac-gate.co.jp/feed/index.html

jimlab

Gotta love Alta Vista's translator...

fd3s777

iTrader: (3)

hehehe I got my brake from a 2001 FD. brakes are larger (330mm) I do really feel they brake alot better than U.S spec.

rynberg

OEM '01 FD brakes are 12.4", or 315mm

There will be zero difference in stopping power on the the street between those and the OEM 93-95 brakes, except from speeds that exceed the ABS threshold (hint, very high). It is certainly possible that they have better feel than your old brakes, and they probably require less pedal effort/distance as well.

fd3s777

iTrader: (3)

really... I guess they are just newer. Feels better.

Scrub

iTrader: (25)

did you ever consider the old brakes could have had problems?

Node

iTrader: (1)

Oh god, are they going to start selling e-bay big brake kits now?

spiceboy82

unless ive missed it does anyone know if there is a link for the JBT brake kits?
cheers

SlingShotRX7

See what you guys did..

Now he's selling his brakes..

https://www.rx7club.com/showthread.php?t=424091

jpandes

Don't give the crap about spending money on big brakes... He may get bitten by the "track day" bug. Those will come in handy! $1495 is cheap, too.

Prôdigy2nd

iTrader: (3)

wow holy crap, this is kinda funny, cause i just learned all thise brake crap in my AST program and forgot it all, but i beileve the reasont the 929 master cylinder will incresase brake efectiveness is rather simple i believe. the whole design behind the internals of the 929's probly allow it to shift more brake fluid at once, thus resluting in the brake pedal being depressed less then originaly, but same amount of flius shifting. Also if you put 50lbs onto the brake pedal with stock setup then change it to a Big Brake kit setup, then you will still put 50lbs worth of pressure on the brake pedal but since the amount of fliud that needs to get shifted is higher the pedal falls father to the floor. In the 929 i believe that it shifts more brake fluid through the lines therfore "stiffing" the pedal feel, this should also allow for harder braking applications because you can shift more fliud in the same amount of pedal travel. well thats my ranting and raving, i'll try to help clear this mess up if i can in the next few days.




Prôdigy

Kento

It's called "master cylinder piston ratio", and although I've heard good things about the 929 master cylinder used with brake upgrades, simply going to a larger master cylinder piston on any application won't necessarily "allow for harder braking applications" because if you use too high of a piston ratio, the brakes become "grabby" and lose a lot of feel and modulation.

Improved FD

the stock master cylinder is notorious for spongy feel and lack of initial bite....I've talked to several people who said the 929 makes a night and day difference with the stock brakes

I'll follow up as soon as I get mine installed