Q: Why is my brake pedal soft?
A: The usual cause of this issue is air trapped in the lines or the calipers. Bleeding the system may help. Don’t force new fluid into new lines; that might cause foaming, which makes bleeding extremely hard.
Important: The caliper bleeding screws MUST be facing upward!!
Is all of the air removed from the system? If so, the booster pushrod that’s under the dash may need to be adjusted to lengthen it (some can’t be adjusted). Don’t go overboard; if it’s too long the fluid won’t return and your brakes will drag. Use ¼ turn adjustments and check after each. SSBC offers adjustable pushrods for many vehicles.
If the booster to master cylinder pushrod can be adjusted, you might try that as well.
If after trying the above the issue persists then you might have a failing master cylinder. Before replacing it first ensure that you removed all the air from the system. Always bench bleed prior to installing a new master cylinder. If you didn’t, remove the master cylinder and bench bleed it. Instructions for doing so are below.
Q: Why does my vehicle pull to one side when I apply the brakes?
A: Because the caliper on that side is the only one that’s working.
Rebleed the opposing side then try braking once more.
Q: Why can’t I feel the power assist?
A: The booster might not have the vacuum it needs to work properly. On engines with high lift cams sufficient vacuum may not be generated. A booster at idle needs a minimum of 16 inches of vacuum to function correctly. You may need to add a vacuum pump if your engine doesn’t provide this.
A vacuum leak may also be the culprit. Leaks in the manifold or the hoses can cause vacuum problems. Also, the booster itself might be defective. The way to determine the issue is to perform a vacuum test. Does the booster hold a vacuum for at least 3 minutes after the engine is off? Then you’ve got a good booster.
Important: ALL master cylinders MUST be bench bled in a vise before installation!
Q: What’s the proper method for bench bleeding a master cylinder?
A: Use a vice to secure one ear. Push the piston in with a large screwdriver. Using clean fluid, top off the reservoir. Attach our M/C bleeding kit or a dummy line to the two ports. The front line should run to the front, the rear one to the rear reservoir. Stroke the master slowly. It should return slowly, creating plenty of air bubbles inside the fluid. Stroke slowly again, doing so until there are no more air bubbles. Then stroke 10 more times to ensure a hard pedal. The instruction sheet for SSBC part #0460 has more details.
Q: How do I choose the best pads for my vehicle?
A: Ask yourself how and where you drive. Stop and go conditions warrant a different pad than the stress of racing does. SSBC customer service can help you in choosing the proper pad.
Q: How can I know when to change the brake fluid in my street vehicle?
A: By looking at the color. Brown fluid has been contaminated by water and dirt and should be replaced. DOT #3 and #4 fluids absorb water. Don’t use silicone fluid for track racing.
Q: How do I tell the master cylinder’s front reservoir from the rear one?
A: Generally, the front one is larger than the rear. In a select number of vehicles they are the same size, however. GM vehicles use the rear reservoir for the rear brakes. On Ford the front reservoir works with the rear brakes. In most cases the disc brakes are fed by the larger bowl.
Front wheel drive vehicles have brakes that are diagonally split.
The cylinder has four bowls, one for each wheel. That’s crucial to remember when installing a residual valve, distribution block or proportioning valve.
Q: Where should a proportioning valve be placed?
A: After the distributor block and before the rear flex hose. Never, ever install it between the master cylinder and the distributor block. If you do you will have a very soft pedal.
Q: When should the flex hoses be replaced? Will I be able to tell from a visual inspection?
A: Flex hoses do a lot of work. They move up and down continuously like shock absorbers while under high inside pressure. Over time their interiors will collapse, blocking the flow of fluid.
To be safe, install new hoses whenever the calipers are worked on, even if they look fine.
Q: Will replacing my flex hoses make my pedal harder?
A: Sorry, no. However, when you do replace them you should always bleed the system. That will make the pedal harder. Take your time and always do brake bleeding properly.
Q: Can a soft pedal be caused by the flex hoses expanding?
A: Only in very rare circumstances. The number one cause of soft pedals is improper bleeding that allows air in the system. Flex hoses are tough; they’re designed to withstand 3000 PSI.
Braided stainless steel hoses look great, but they’re not necessary for fine brake performance.
Q: I want to stop! How much brake pressure will it take?
A: A normal stop will generate 1200 PSI, whether or not you have power brakes. In emergency braking conditions 1400 PSI is common. If the factory installed a proportioning valve then the rear brakes only create 600-700 PSI.
Drum brakes need less PSI because they have a quicker grab. Installing rear disc brakes can raise PSI to 800-1000 PSI or more.
To ensure that your brakes are creating enough pressure, use SSBC part #A1704, brake pressure gauge. If a vehicle isn’t generating at least 600 PSI then don’t drive it. It won’t stop!
Q: How many pounds of torque should be my wheel bearings be tightened to?
A: For rear drive vehicles with separate bearings and races, bearings usually require 12 -15 foot pounds of torque, though you might need to back off just a bit so the cotter pin will fit. Always use a torque wrench and never over tighten, as this will reduce bearing life.
If your vehicle has one piece sealed bearing or hub assemblies refer to your service manual.
Q: What kind of differential fluid does my rear axle require?
A: For Positraction, a hypoid or limited slip additive is best. Use the one meant for your particular rear end. For non-Positraction vehicles, any 80-90 weight gear lube is fine. Change the fluid frequently if you’re are towing, pulling a trailer or engaging in other high stress uses, as it does degrade over time.