3/20 proportional valves

[MMamdouh]

i have premature rear lockup under braking after my rear disk conversion... after doing some research i found out that i should be using 3/20 proportional valves and those are a problem to find for the Opel/vauxhall guys and their are no 3/20 for daewoos which makes it almos impossible for me to find specially that the opel astra versions that came with rear disks never came to Egypt ... i am currently running 3/30 valves as those are closest match for the time being but they are still dangerous (i almost lost the car last Thursday)

now i would like to know what is the difference between the 3/30 and the 3/20 valves in terms of composition... i know the valve is made of a housing and a spring and a ported valve and the only difference i could find between the 3/40 and 3/30 valves is the spring... it is some 20% longer in the 3/30 valve

i imagine that the 3/20 valve will have an even longer spring but i need someone to confirm that... if this is the case then maybe i can replace the 3/30 spring with a longer (stronger) one and add more reduction to the pressure going out of the valve to cure the lockup issue so can someone confirm this piece of inf??

MMamdouh

[MMamdouh]

2 hours of searching on the internet... finally understood the numbers marked on the P valves

http://jenniferandjon.com/ABRacing/inde ... &Itemid=48

3 refers to the proportional increase in rear pressure compared to front... in our case it is 3 bar increase in rear pressure for every 10 bar for the front... this will reflect the inclination angle on a graph showing the relation between front and rear brake pressure

20, 30 & 40 refers to the pressure at which the proportioning starts... 20 refers to 20 bar, 30 refers to 30 bar and so forth, this will identify the knee point on a graph showing the relation between front and rear brake pressure

in my case this means i am stating the proportional effect at 441PSI of brake pressure whereas i should be starting that at only 294PSI... also at 500PSI front brake pressure i am getting 100PSI more than required to the rear brakes

now i got to figure out which component of the P valve affects which characteristic... does the valve port affect proportioning value and the spring strength affect where proportioning effect starts??

MMamdouh

[Daniel]

does the valve port affect proportioning value and the spring strength affect where proportioning effect starts??

Hi MM,
Seems logical to me that spring strengh set the knee point. For proportioning value (slope) I would have said it's set by the shape (area) of internal piston.
Why not use adjustable proportioning valves?

Some "white papers" about brakes: http://www.stoptech.com/tech_info/tech_ ... pers.shtml .

[Daniel]

You should have a look at this site in french http://www.unchemin.org/cours/freins/28 ... einage.pdf . From pages 18 to 33 there is some kind of "animation" for uncompensated proportioning valve.
The slope is set by area ratio while knee point is set by spring tension.

Hope it helps,