Fat Larry’s Garage Brake Quetion

[Fat Larrys Garage]

Just wondering if anyone put residual valves in their brake system the last two cars I built I put them in the brake systems

[DanQ]

Are you referring to a residual check valve, usually placed in the port on the master cylinder, and maintains 1-3 psi of brake fluid pressure after releasing the brake pedal? I was taught residual valves are for drum brake applications only, and are used to prevent the return springs from pushing the wheel cylinders all the way in, causing low brake pedal. I would have to assume most of us are all running disc brakes on our projects and therefore would not want residual valves, as disc brakes needs the brake fluid to free flow as when they retract. A residual valve in a disc brake system will surely prevent the square cut o-ring on the caliper piston from returning fully, causing the brake to drag. Would you be referring to the proportioning valve, by any chance? A proportioning valve is a great safety device to save one brake system in the event of the failure on the other side of the system, and it notifies the driver when there is a pressure differential in the system by lighting up a brake warning light on the dash.

[edwardb]

I have not put residual valves in any of my builds (all 4-wheel disk systems) and have not seen them mentioned or discussed on the forum in 10+ years.

[Skuzzy]

DanQ is right. You do not want to install residual valves on a disc brake equipped car. That will cause problems.

[Jkviper]

Larry,

Here is an excellent video on why you would use a residual pressure valve. Basically they are used in disk brake applications where the master cylinder is below the height of the calipers.

https://youtu.be/DIVDjqniUX8?si=UUEEIfqYaw24CU8m

[Skuzzy]

Yes, if you are mounting the brake master cylinder lower than the calipers you will need a check valve. I always use an adjustable check valve, rather than a fixed residual valve, for that purpose so it can be set to keep the calipers from having too much pressure causing drag and excess heat.

I considered that situation in a Coupe to be really unique and not neccessary.

[Fat Larrys Garage]

Thanks everyone for your reply’s makes a lot more sense now that I think where the master cylinder was on some of my other builds

[Skuzzy]

One other thing to mention. Make sure your brake lines never get above the master cylinder, when you are running them.