I thought there were three different factory brake bias bar valves for 928's.....the early 78-79 that had the smaller 9" booster had a 55 bar valve....then the 80-86.5 had the 32 bar valve and S4+ had the low 17 or 18 bar valve....

A common upgrade for track driven 928's to improve rear braking....

I just looked in PET and it appears there only is two...the 32 and 17?

2nd ??? My racer has the early 9" booster with GTS front and S4 rear brakes...the pedal is a bit on the firm side.....how hard is it to change to the larger 10" booster to reduce pedal effort?

 

Should'nt be that hard. I'm thinking lees than a day for two guys .I would change the master cylinder too so you have a matched system.

 

Test #1 is installing your rotors and pads...... I'm guessing thats probably 90% of the improved braking vs mine

 

IIRC the 55bar one was a 911 part.

Myles

 

Easy to change , bolt the old unit off and change to the later unit , Jost done that on my build using the early hydraulic lines and master , dont know how it will all meld together yet as havent got any fluid in the lines yet. But all fits in.

 

Brake bias also depended on market at least 84-86.5 with antilock.
Euro had 33, USA 18.

 

Brake Bias Valve 60 bar 965 355 305 01
Brake Bias Valve 55 bar 964 355 305 10
Brake Bias Valve 45 bar 964 355 305 00
Brake Bias Valve 33 bar 928 355 305 02
Brake Bias Valve 18 bar 951 355 305 01

 

I agree with RKD on the brake bias valves "available". I've used everything but the 60 bar at various times, and settled on the 45.

Last I heard, it was NLA from Porsche (except Roger can probably get it!!! - Ha). That 45 bar valve was used on 964 models of the 911, and those guys frequently "supersize" their bias to 55 or higher. Sometimes they have the one they removed tucked away somewhere - that's how I got the two I'm using.

Gary--