slips2

Yes, I've kept the stock P/V.
The new suspension, wheels & tires, and rear brake upgrade have combined to produce significant handling improvement - very pleased.
First roadtrip since the upgrades was to the local mountains this past weekend:



Climbed from sea level (home) to over 7,000 feet via winding mountain road switchbacks. Woo-hoo, what a ride!
My wife and I are the original owners, and now our 964 is "new & improved" with 77K miles on the odometer.
We think it's more engaging and fun to drive than a recently owned 997.

As regards braking, my impression is as follows ... prior to the upgrades, under hard braking the stock 964 felt somewhat like it was "standing on its nose" and there was the very near potential for push/understeer if simultaneously in a turn. Now, after the upgrades, under hard braking the feel is more like the car "squats down" at all four corners, as if it's being pulled into the pavement. In addition, the Michelin 225 PS2s up front delay the onset of understeer. YMMV.

The late 964 4-piston (30/28mm) calipers have less piston hydraulic x-sectional area than the '90-91 2-piston (40mm) calipers, if that's what you're replacing. Without other brake system mods, the result is less rear brake torque (thereby work) at any given braking level. For more rear brake torque, to levels as intended by the factory during harder braking (higher brake system fluid pressures), you may want to replace the '90-91 stock 45-bar P/V with a 55-bar unit as came on late 964s.

christallon

Thanks Slips,

Yes, I'm replacing the 90-91 2 pot with the 92/93 4 pot calipers. I understood from your post that I will not be able to utilize the greater braking aspect of the larger calipers due to smaller P/V allowable pressures.

Has anyone simply bolted in a later set of calipers, as described above, without changing the P/V valve and experienced better overall braking? I made the change assuming it was an upgrade.

Cheers...

slips2

By my calcs your brake hydraulic bias ratio is 1.72, which relative to what you had (1.50), indicates the fronts will carry more of the braking, especially during hard braking without an upgrade to the 55-bar P/V. Should be stable with less chance the rears would lock-up first, that's with no regard to ABS intervention or other changes. I'd be interested to know how it feels during threshold braking, once the pads/rotors have been bedded-in.

Last item, will need to save-up.

sturm

Bill is the guru on this (and many other) subjects. I will add that some years ago a rennlister (or maybe p-fans) measured his before and after pad wear with his STOCK 964 brake set-up after a day at the track. As I recall, his rear pads had very minimal wear especially compared to the fronts.

As result of this he installed a different proportioning valve (turbo 964?) that provided greater rear bias and he had no detrimental effects from this

Just an FYI


'93rsa 3.8