Thomas Baumann

Hi every one
I was thinking to mount 993 TT Big Red (disk:322x32) as front break upgrade to my C2 and use the C2 original front break caliper in the rear and replacing only the disk. I found adapters letting me fix the caliber correctly as well as disks. All OK.
The C2 front caliper differs from the 993 TT rear break caliper with slightly bigger pistons. So I thing that to keep the optimal bias between front and rear some things (like break pressure regulator) must be adapted
Is that possible?
Has any one of you done this?
What is you experience if any?
Cheers

ThomasC2

Discussed a 1000 times here. Do a search.

But in short... not recommended. They are too powerful and will give you a dangerous balance. Find a pair of 964 or 993 C2 rear calipers.

Thomas Baumann

Thank you for replying
Well I did search, but the search function on this site is quite cumbersome, that's may be the reason the question is asked and answered a 1001 time :-)
But could not proportioning valve help adjust the pressure going to the rear calipers?

FormulaRX

You need to upgrade to 993 C2 rear brakes along with the 993 master cylinder. The stock 964 C2 master cylinder is not sufficient for 993 big reds

Thomas Baumann

I was thinking about some thing like this but placed under the bonnet
https://rennlist.com/forums/attachme...-s2-tilton.jpg

Bill Verburg

The 2 issues are
1) rotor size the 964 front wants a 26mm min 28mm nominal and can be used on up to a 32mm rotor, at 24mm the 964 rear rotor starts out 2mm undersized.

2) brake bias. a 911/964/99 wants ~1.5 overall brake torque bias, the low end is ~1.4 and that requires that the car be carefully setup to utilize it. w/ 964 fronts in back you approach 1.0. Have some guys done this? yes, but they get away w/ it by being very good and by never skirting over the line pressure where lock up at the rear happens, This isn't all that hard to do when you are thinking and in full control, in a panic it's another story. The bottom line is that for safety you want the fronts to lock a tad before the rears in a panic stop.

a p/v helps w/ a minor imbalance but isn't so good at that much discrepancy, to correct that big an error you would want an adjustable twin master setup.

a 993 rear w/ 993RS/t front is ~1.65 front below the p/v knee and ~3.07 above the knee. You can run w/o the p/v to give ~1.65 all the time.

The best bias I have ever experienced is the thru '83 911 @ ~1.49 and the 993RS/Cup/RSR @ ~1.43

W / cockpit adjustable twin masters the latest 991RSR runs 1.3 to 1.9

Thomas Baumann

@Bill Verburg
Ok me trying to be smart while reusing my front break as rear ones will not work without major investment...
Further I understand that the 993RS brake system is best...
from following link
http://forums.pelicanparts.com/uploa...1359425821.gif
I can see that the pressure for 993RS is at 40bar but the 964C2 is at 45. Will that have an influence? Or is this just less pedal pressure from the driver?