How do brakes stop a car?
When you depress the brake pedal, hydraulic pressure is created in the master cylinder. The cylinder is filled with brake fluid which is pressurised along a series of brake pipes and hoses to the hydraulically activated pistons in each wheel's hub assembly that force the friction material on your pads or shoes on to rotating parts (disc brake or drum brake), causing your car to stop. When braking, 80% of the braking force in a car goes through the front wheels.
Like all components, brakes deteriorate over time. As it happens gradually, many people don’t notice the difference. As new cars continue to get more powerful, so this deterioration can become more and more dangerous.
If you’ve noticed any of the following, your brakes require inspection.
- Grinding noise when applying the brakes. Your pads could be excessively worn and needing to be replaced along with potentially damaged discs.
- Your car pulls to one side when braking, this usually means a sticking or seized mechanical or hydraulic component.
- Your brake pedal feels spongy, there could be air in the hydraulic system due to a brake fluid leak.
- Soft Brake Pedal. If the brake pedal is limp and goes all the way to the floor, this indicates a serious braking system fault which you should have inspected immediately.
- Your brakes pulsate, you could have a distorted brake disc or drum.
- The brake warning light on your dash illuminates.
- The handbrake is pulling up higher than it should (more than 6 to 8 clicks in modern cars).
- Squeaking, there are many reasons why brakes squeal. It could suggest the brake calliper has stuck and the brakes pad remains partially applied to the disc but some pads have wear indicators that squeal when worn to let the driver know the brakes need changing.
When to replace your brakes
Different driving patterns have a dramatic effect on how often your brakes need servicing. For example, a set of brake pads could last up to 60,000 miles or more on a car driven mostly on the motorway. However, the brakes on the same car driven mostly in busy city centre traffic may last only 25,000 miles or less.
Front brakes normally wear out before rear brakes because they handle a higher percentage of the braking load, especially on front-wheel-drive cars.
It is often recommended that brake pads should be replaced if the pad friction material has worn down to a thickness of 3 millimetres. Brake disc thickness should be measured if they are at or below the manufacturer's safe minimum thickness specification they should be replaced.
Questions and Answers
What is included in a brake inspection?
During a brake inspection, the entire brake system is checked. This includes the following:
- The brake pedal.
- Brake fluid.
- Brake lines and hoses.
- The brake assemblies (whether they are disc brakes or drum brakes).