911Jetta

Your knowledge and thoroughness is simply amazing! Wow.

964russ

Bill.
Forgive my ignorance.
My c2 is on 993 fronts with the larger twin pot rears.
Do you recommend I change the bias valve?
I think its brakes well, smoke & lock ups when drivin hard!
But you can never have too much brake!

964russ

And bill.
You are the brake Oracle.

FeralComprehension

Don't bull**** your besties; we know better...

BLACK-BETTY

Two questions,

Did your pads need filing down to avoid over hang on the discs....

Mine did. Although Grant didn't and has no probs. Mind you we're running different front callipers.

I assume you are running four pot rears? Otherwise your brake bias would be way out?

Congrats on the mod. For me the most enjoyable aspect was how less pressure was needed on the pedal. Inspired so much more confidence.

Cheeksyboy

The only problem with my car is the monkey behind the wheel!

Bigger breaks aren't a must for track work as Boxsey has shown over many years, but a nice and reassuring upgrade when on long runs. Like Boxsey i found break ducts made a huge improvement in reducing brake fade due to temp increases.

I'm so glad Bill is on this forum....is there anything you don't know Bill? Hats off to you.

STUARTQ

Steve, Bill, anyone else,

I'm replacing sometime in the next few months the standard rear calipers on my C2 with C4 calipers.
The discs are cross drilled.
Will I need to make any other adjustments?
Fronts

Rears

Cheeksyboy

What do you have on the front?

STUARTQ

From what I've been told just the standard front calipers with cross drilled discs.

Just noticed this is my 1000 post

Is that good or do I need to get a life! Hehehe.

boxsey911

The pads fit fine without over hang so there was no need for filing anything off the top or bottom. Yes, I did the four pot rear conversion a while ago. I have the 55 bar p/v in at the moment but will most likely gut that to shift some bias to the rear (as per Bill's suggestion).

boxsey911

All you need to go with it is a 55 bar valve in place of the existing 45 bar valve. The valve sits in part of the ABS unit. That was the first conversion I did.

I forgot to mention in my first post that we removed the spring plates on the used 993 calipers and cleaned up the minor amount of corrosion. It's always worth doing this on used calipers so that you don't run in to issues later down the line of pads not fitting in them.

boxsey911

Mr.Alex

Hows the RS shifter in terms of notchiness? On occassion I'd really like a shorter throw, but I really wouldn't want the notchy feel that occurs when pushing the gears in.

Bill Verburg

assuming you are using 304mm front rotors and not 322s front is 2306 rear is 1309nm and bias ratio below 45bar line pressure is 1.762 and above is 3.262
For street use that's fine, though you can profitably use a p/v w/ a higher knee or even get rid of it entirely

Keep in mind that some of the best 1 stop braking on the planet in a car is the '69-83 911 w/ a ratio of 1.491

By going from 1.7 to 1.4 you move some of the heat, wear and brake torque to the rear and off the front, that's a good thing, but you don't want to go to far as you do want the fronts to lock before the fronts at all times
Ii have 1.426 on both of mine, having an effective lsd and a low stiff car helps to put more rear to work

Bill Verburg

964 4 pot rears have less brake torque for the same line pressures as the 2 pots, this is because the slave piston area in the 2 pots is larger.

993 4 pot rears have more brake torque than 964 4 pots for the same reason.

oe the 4 pots come w/ a 55 bar p/v and the 2 pot rears come w/ a 45 bar valve

again std 964 2pots ratio below 5 bar is 1.734 above 55bar it is 3.21, the 2 pots below 45bar are 1.683 and above are 2.792

I'd take steps to get more rear
possibilities are p/v w/ a higher knee ie 55 or60 bar valves for a small increase in rear above the knee

gut or remove the valve all together to eliminate the knee distortion