[Lplus10]

Anybody have a 2 lb residual pressure valve on the front, disc brake circuit? Has it improved braking? -or- why is this a dumb idea? ::

 

[Ronstang1966]

Why do you want to wear down your pads and rotors prematurely and decrease gas mileage? Disc brakes require no residual valve. Drum brakes use them because there are springs pulling back on the shoes that would force fluid back into the master cylinder and pull the shoes too far away from the drum, severely hampering braking performance.

 

[grentis]

Well i always thought that factory master cylinders have residual valves built into them. And today some master cylinders do not have them built into them and require an external valve to work. Factory master cylinders have a 10lb residual valve built in for drum brakes and 2lb built in for disc brakes. They have them in the master cylinders to keep the pads or shoes near the rotor or drum.

 

[Ronstang1966]

You may get away with 2lb residual valves but I have never had any in my cars and have no complaints with braking performance. The pads need to pull away from the rotor to cool. Even with only 2lbs of residual pressure I do not see how they would pull back as there are no springs like in a drum setup. I will stick with no valves.

 

[Lplus10]

Appreciate the comments - sounds like it's a dumb idea on my part. I was hoping to increase braking force and responsiveness but it sounds reasonable that that 2 lbs is just going to keep the pads up against the disc. Thanks

 

[grentis]

Go here to understand what a residual valve is for. I don't think you understand what it is for. Cause it sounds like you want to add a 2lb residual vavle on a factory master cylinder that already has on in it. It will not help in breaking but will cause them to lock up. If you buy a Dual Master cylinder like the one i have, which is a JMC dual master cylinder, you have to have a residual valve for disc brakes or it will cause a soft pedal until the pads were actually applied to the rotors. The residual valve just stops all the fluid from calipers or wheel cylinders to flow back up into the master cylinder.

 

[Helmantel]

67fastbackguy: Residual valves for disc brakes are usually used when the MC is mounted lower than the calipers, as in a hot rod (where it is mounted under the floor). It's actually one of the first things they mention in your link. ::

There may be other applications, but as far as I know, you normally don't use one for disc brakes.