Fatdaddy

I’m going to install wilwood disc brakes on the front of my 62. I plan on using a 10 lb residual valve on the rear drum brakes. After reading numerous post I still don’t know if I should use a proportioning valve on the rear or not. Some guys say you do some say no. Maybe I should put one in the line just in case. But I really am curious if you do need one. Does anybody know for sure?

Easy Rhino

Depends on not just your front brake set up but both your front AND your rear brake set up.

So, what are you using for rear brakes?

Fatdaddy

As posted rear brakes are drum.

Easy Rhino

With using the 10 pound residual valve, I don't know the answer. Why not use a proportioning valve instead to allow adjustment?

Fatdaddy

A residual valve and a proportioning valve do different things I think.

65GGvert

I had to put an adjustable proportioning valve to the rear drum brakes on my 60 with front discs. Single master cylinder system. Rear wheels would lock up long before fronts did anything without it. I tried it with and without residual valve, came out the same. So I took the residual valve out so the front disks wouldn't rub all the time. Everything's okay now, rolls free and the brakes stop equally

Fatdaddy

Does it make a difference if you use a single m/c or a double m/c ?

Powershift

Factory built cars with disc in front and drums in rear used both a proportioning valve and a residual valve.

Larry

Powershift

Yes..........many single master cylinders for (all) drum brakes had the residual valve in the mc. If you go to discs in front and drums in rear you do not want this.....as it will cause drag on the new front calipers.

With a dual mc you may be able to get the front reservoir without anything and a rear reservoir with a residual valve. Then you just add a proportioning valve.

If the mc does not have a residual valve you can add it in the line to the rear. I think the combination of a proportioning valve and a residual valve was called a "combination valve"..........although the type valve may also have provision for a brake failure light (if you also wanted that).

Bottom line, make sure you know what you have and what you are ordering.

Larry

alexandervdr

I converted my 64 to front disk brakes, kept the rear drums, converted to dual MC. I have a 10lbs residual valve on the drums (for all I know the valve is simply mandatory). On the front disks, there is a 2lbs valve, that one seems to be optional (according to the vendor of the disk upgrade). I have installed a proportioning valve, and I needed to tune down rear brake force substantially otherwise the rears locked up way earlier than the fronts.

Fatdaddy

this is what I’ll probably do

Factoid

Residual valves are need for two reasons. One, when the MC reservoir is lower than the calipers/cylinders (think older cars where the MC is under the floor). Then you must have the blue (2lbs) valve for discs and the red (10lbs) valve for drums to prevent the fluid from draining back to the lower MC. Not an issue for our cars.

Two, when using drum brakes with discs. The red valve prevents the drum shoe springs from pushing the cylinders (fluid back to the MC). Nothing is required for the discs. One of the many advantages of discs over drums is the range of brake pedal pressure before the pads lock the disc. This gives you more control and braking finesse. Drums on the other hand provide a more limited range before lock up, but they will lock up before discs. Using a proportioning valve in the rear drum circuit allows you to attenuate rear braking to balance overall braking. Remember, the only thing the p-valve does is reduce pressure to the rear brakes based on the adjustment of the ****.

Long story short, use both!