You have to explain, "brakes were not really there" better. If the brake pedal is solid and as high as normal, but the car doesn't stop is easily as normal, the linings on the pads could be glazed. That's all too common with brand new pads. They haven't worn yet to match the microscopic grooves in the rotors, so braking power is reduced. That means we push harder on the pedal to stop, and that increases the amount of heat being dissipated. The higher temperatures melts the binders and resin in the lining material, causing that glazing. That glaze is like a hardened varnish with less friction, so braking power is reduced more, and we push still harder on the pedal to stop. When this gets bad enough, we scrub the new pads with a wire brush or sandpaper to remove that coating. Another trick is to lightly machine the rotors to true them up and form small grooves. Those grooves will grind the coating off the pads.
The best way to prevent glazed rotors and pads is to perform a test-drive after installing them. That test-drive includes two or three rather aggressive stops from highway speed, with time in between for the parts to cool down. That gets the linings worn to match the rotor so they make full contact, then the increased friction means it takes less pedal pressure to stop, and the brakes run cooler.
Braking power could also be weak yet just because the pads are new or the rotors were just machined. Anything that changes the amount of pad surface that contacts the rotor's surface reduces friction and stopping power. If the brakes don't become overheated, braking power will gradually come back to normal. In fact, we tell customers to brake carefully for the first 100 - 200 miles to give the new linings time to seat.
One thing that should not be an issue is the quality or composition of the pads and shoes. All manufacturers put a real lot of resources into developing brake systems that are balanced front-to-rear. The variables include master cylinder piston diameter, caliper piston diameter, rear wheel cylinder diameter, pad and shoe lining surface area, and weight distribution including with or without air conditioning. The weight distribution variable is handled with the spring-loaded valving in the combination valve and, when used, the rear height-sensing proportioning valve. All of these things work together to ensure the front and rear brakes do their share of stopping with no tendency for easy wheel lock-up. One variable that gets factored in is the "coefficient of friction" of the lining material. That means how well it grabs the rotor and tries to stick to it. Every manufacturer of aftermarket replacement shoes and pads has to adhere to those values. If their material has a higher coefficient of friction than the original parts, the surface area will be smaller to offset that. This is why we don't believe advertising that says their pads will stop faster. The best you can do is have a brake lock up and the tire skids. The cheapest pads and shoes will do that, so how can you have some replacement part that stops faster?
What some aftermarket replacement pads and shoes CAN do is be less susceptible to another type of brake fade. That involves "off-gassing" of the lining material when it gets hot. That's the same high heat that can cause glazing, but before that happens, the gasses given off act like a layer of tiny ball bearings between the rotors and linings. The symptom is you can push harder and harder on the brake pedal, but the vehicle doesn't reduce speed any quicker. This is most likely to show up in mountain driving when the linings don't get a chance to cool down.
At the same time, when the pads get that hot to cause off-gassing, that heat migrates into the brake fluid and when it gets over 212 degrees, any moisture will boil and vaporize, leading to a different type of brake fade. Since air can be compressed, it causes a low and soft brake pedal. Couple a mushy brake pedal with ineffective pads and shoes, and you can see why overheated brakes don't stop well.
When glazing hardens, it can become sticky, leading to brakes that grab too easily. If one front brake is affected more than the other side, it can cause a brake pull on some car models. Most front-wheel-drive vehicles use a "split-diagonal" hydraulic system, meaning the left front and right rear brakes are on the same hydraulic circuit. If a leak develops in one circuit, this leaves you with 50 percent of your brakes. With the older front-rear systems, if a leak developed in the front circuit and you only had rear brakes, you'd have roughly 30 percent braking power with rear-wheel-drive cars and only about 20 percent with front-wheel-drive cars. They have a higher percentage of weight in the front. The split-diagonal system ensures you still have one working front brake.
In older rear-wheel-drive vehicles, if you'd block off fluid flow to one front brake, the one working brake would tear the steering wheel out of your hands with enough force to break wrists. Two working brakes offset each other when the wheels are tied together through the steering linkage. With the split-diagonal systems, and a leak in one side leaving you with just one working front brake, the geometric relationship of the suspension parts and alignment angles have been modified so the braking forces cause that wheel to pull toward the center of the car. That offsets the hard brake pull that's making the wheel turn away from the car. Chrysler has that so well perfected that the only way to know there's a leak in the system is by the red "Brake" warning light on the dash. For most other manufacturers, if you pay attention, the most you might see is a tiny wiggle in the steering wheel, but the car will still stop in a straight line.
The suspension geometry is also important when the model is available with anti-lock brakes. The ABS Computer will block fluid flow to a wheel that's slowing down faster than two of the others, then bleed off fluid pressure if necessary to get that wheel back up to speed, then reapply stored or pedal-supplied pressure to reapply that brake. This "block, bleed, apply" sequence can occur as fast as 30 times per second but 15 is more common. That's what causes the buzzing you hear and feel in the pedal when the system activates. The point is a normal condition is to modulate brake fluid pressure to just one brake. You don't want to have a brake pull when that happens, so the geometry of the suspension system parts works for anti-lock brakes as well as for the split-diagonal system.
As a point of interest, vehicles with anti-lock brakes will usually come with rear disc brakes. Caliper pistons require very little movement to apply its brake so they respond quickly to modulating brake fluid pressure. Drum wheel cylinders and shoes have to move a lot to push the shoes out to the drums before any braking force can be developed. That typically takes way too long for ABS function to be effective. The exception to this is on trucks with the less-involved rear-wheel-ABS, (RWAL) systems. Those use a dump valve under the driver's seat area, on the frame rail. All they do is when the two rear wheels slow down too quickly, the valve blocks additional brake fluid pressure to the rear wheels, or it dumps the fluid pressure until the rear wheels get back up to speed. It's okay that this takes longer to activate. The goal is only to prevent the rear of the truck from trying to pass the front. Skidding tires have no traction, so their stopping power is gone. Stopping distance is increased, but directional control is maintained. The goal of four-wheel-ABS systems is not to reduce stopping distances, although that is an additional benefit on many models. Instead, the goal is to maintain steering control by preventing skidding tires, so you can steer around the car that ran the red light.
One of the more frustrating and confusing causes of poor brakes due to a low and mushy pedal on vehicles with anti-lock brakes is air that gets trapped in the hydraulic controller. Brake fluid flows back and forth through the bottom of some chambers with valves at the top, where, coincidentally, is where air can get trapped. The only way to expel that air is to open the valve, then push that air all the way to the wheels to bleed it out. Those valves can be made to open while driving the car and putting it into a skid, but without the bleeder screws open, the air can't travel to them. The only way to get that air out is to perform a brake bleeding procedure with a scanner. With that, you can talk to the ABS Computer and command it to open the valves. The steps are listed on the scanner's display. It will tell you to open one bleeder screw while your helper is pushing on the brake pedal, then do that again at a second wheel. This all takes less than a minute but it's the only way to get that air out. To my knowledge, only the Bendix-9 system on GM vehicles and the Bendix-10 on Chryslers, all from the early 1990s, will bleed without a scanner or any special procedures. There are likely some other systems, but the majority do need the scanner. This is why it is so desirable to remove air without allowing it to flow down to the wheels. If the calipers are replaced, the air in them can be bled out like normal. That air won't go backward into the hydraulic controller unless the hoses are left disconnected so long that the brake fluid drips out of them.
To get back to your question about bleeding, the only reason to do that is if there's air in the system. Even very small bubbles in the lines leading out of the master cylinder can be ignored. They aren't going to float down to the ABS controller or the wheels. When you push the brake pedal, brake fluid goes down the lines, then the air floats back up. When the pedal is released, the air bubbles wash up into the reservoir with the fluid that's rushing back. This is one of the tricks I briefly mentioned earlier. It has to do with replacing the master cylinder. I can go into more detail, but it works best for car models other than Fords. It still works, but many Ford models have four lines leading out of the master cylinder instead of just two. Regardless, it is pretty easy to replace a master cylinder without having to bleed at the wheels. That eliminates a lot of heartache and frustration when air gets pedal-pumped down to the wheels and gets trapped in the ABS hydraulic controller.
In your case, when you're just replacing old brake fluid with new, there's no reason air should get into the system if you don't let the reservoir run empty. Just run new fluid through to each wheel until you see reasonably clean fluid show up.
You also made a comment a while back about the bleeder screw being on top of the caliper. That is correct as that's where the air will be. Chrysler, for one, is famous for parts interchangeability, and as such, you will commonly find calipers with two flats where the hole can be drilled for the bleeder screw. The only difference between the left and right calipers is the location of that bleeder screw and hose connection. The result is either caliper can be mounted on either side. I actually ran into one that had a left caliper on the right side. Come to find out the auto parts store didn't have one side in stock, so the owner put the wrong one on, and held it upside down to bleed it. GM is famous for just the opposite. They like to make mirror images of their parts so nothing can interchange from side to side.
Apr 10, 2026 at 7:22 AM