Attn Adney Re: Proportioning valve

I posted this yesterday in a thread dated 12/24/03, so I decided maybe I need to do a re-post!

Jim, I suspect there's a difference between a modern proportioning valve used largely in the hot rod market and the proportioning valve VW used on the buses - am I correct? The one used on the buses was inertia reactive with the steel ball rolloing to partially block the outlet port to the rear brake circuit. That said, would a modern hot rod market proportioning valve work to balance the front disk / rear drum circuits if a person was to remove the original VW unit?

How would you recommend proceeding with such an installation, as far as adjusting for the correct balance? In my feeble mind, this seems overwhelming, but could it be as simple as some test skidding on hard gravel road?

I don't know that I want to remove the PV, but over the years there have been some peculiar things happen with my brakes. Years ago, I pulled the PV and replaced it with one I had bought at a wrecking yard and cleaned up inside. What I had perceived at that time to be a bias realated issue (don't remember the particulars) was dramatically improved with the cleaned up PV. I have flushed fluid about every 3-4 years (usually not intentionally!) so that should not be an issue.

It seems to me that sometimes in the past 14 years that in a panic or near-panic stop I had little or no braking from one end or the other whereas I'd try it again after the adreneline subsided and had all 4 working in unison, practically standing on end! The only thing in the circuit that is somewhat flexible in its manner of operation is the PV. Everything else is relative to a slight displacement of a column of fluid and the pressure behind that displacement. The PV is a rolling ball.

From a thread we had a year or more ago, I shortened the rod from pedal to MC and the braking became almost 100% predictable (thank you.) I had adjusted it before that but not enough. Apparently there is enough wear in all the linkage points and enough change in geometry from the front end collision back in '91 that the piston was not returning far enough part of the time, but returning far enough most of the time.

When the AH slams his brakes on directly in front of you, you don't have time to guess if this is a 2-pumper (related to return / not air in line!) or the first application will do it. So many considerations in that split second, like is the shoulder available? Is the guy behind me or the one behind him going to stop? If I swerve will I flip it? Should I try to pull UP on the column? (That trick NEVER works!)

Thanks for the discussion.

- Dave

Reply to
Busahaulic
Loading thread data ...

My response is with the original thread.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

Reply to
Jim Adney

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.