Is a separate proportioning valve needed when converting a 1961-1964 Continental with front and rear brake drums, from a single to a dual chamber brake master cylinder? In other threads knowledgeable forum members toddallen, autostick and jleonard have reported no problems after upgrading to a dual master cylinder without a proportioning valve. With safety in mind, the reason I'm still asking this question is printed in bold in the quote below:
Source: http://www.studebaker-info.org/tech/brakes/bf50014.html Thanks to Gary/kultulz for the link.Proportioning Valve
The proportioning valve is designed to prevent rear wheel lockup during panic braking. It is needed for two main reasons - most vehicles use drum brakes in the rear and all vehicles experience weight transfer during a panic stop. Rear drum brakes are hydraulic over mechanical in design. If too much pressure is supplied to the wheel cylinders, lockup will occur. All vehicles, those with both rear drum and rear disc brakes, will experience weight transfer during a panic stop. When weight is taken off the rear wheels during a panic stop the tendency for the rear brakes to lockup will increase. The proportioning valve is designed to limit the pressure to the rear brakes during a panic braking situation.
The most important point to understand about proportioning valves is when they work - only during panic braking. This means that a vehicle could potentially go its whole life without ever using its proportioning valve. Think about the little old lady that drives to and from church and the grocery store. It is possible that she will never have the need to make a panic stop and therefore never activate her proportioning valve. The other half of that equation is all those who drive near her will probably get a chance to see if their proportioning valves work!
Cheers,
Reijer
Addendum:
This topic has come up before in several threads, I know. But the discussion seems to veer off the road when front (and rear) disc brake conversions are thrown into the mix, as well as when confusion arises over the differences between proportioning valves, metering valves and pressure difference switches.