Good brake performance can make the difference between having and avoiding an accident and having a minor impact or a major one. How do your brakes work, and what can you do to make sure you’re getting the best performance from them?
How Your Vehicle Stops
When you push on the brake pedal, you’re moving fluid from the master cylinder through pipes and hoses to each corner of the vehicle. This fluid enters wheel cylinders that clamp brake pads against discs or push wheel cylinders out, rocking shoes against drums. This friction turns momentum into heat, slowing your vehicle. Over time, these parts will wear down, reducing friction and thermal mass. This leads to longer stopping distances and brake fade.
The parking brake uses a mechanical linkage or an electric motor to apply the rear brakes. This can use a lever built into a drum brake or a screw mechanism inside the caliper. Some disc brakes have a “drum in hat” system with a small drum brake inside the disc behind the hub. While this braking system will work if the main hydraulic system fails, it provides a fraction of the braking force.
Engine braking uses momentum from the wheels to spin the pistons and camshafts when you’re off the throttle. Shifting to a lower gear raises engine RPM, which increases this braking force. Downshifts can keep vehicle speeds down on long descents through mountains. Some cars do this automatically when using the brakes, increasing total stopping power.
Regenerative braking used on hybrid and electric vehicles switches the polarity of the drive motor. Instead of using the motor to spin the wheels, the wheels spin the motor shaft, generating electricity. This can create enough stopping force in electric cars that the brakes rarely need to be used.
ABS and Traction Control
To stay in control of your vehicle, you need to maintain the grip between the tires and the road. Anti-lock braking systems and traction control do this by controlling braking and acceleration.
Each wheel is connected to a gear-shaped reluctor ring, mounted on either the CV axle or the hub. Next to this ring, there’s a magnetic sensor that counts the teeth as they pass by. A computer counts the pulses from these sensors. If it notices a sudden drop in speed on one wheel, the ABS system activates a valve on that brake circuit, briefly reducing hydraulic pressure. This prevents wheel lockup. If wheel speed suddenly increases, the traction control system uses a pump to increase pressure on the brake to keep the wheel from spinning.
Tires, the Most Important Factor in Braking
Most new tires have a tread depth around 10/32 of an inch, and replacement is recommended when they reach a tread depth of 2/32 of an inch. However, it’s safer to replace the tires when they reach a tread depth of 4/32. Once below this depth, the tire can’t adequately channel water away, reducing road contact. This can double stopping distances on wet roads.
Tread depth can be checked with a couple coins. Place a quarter in the tread with George Washington’s head facing the tire. If the tread doesn’t touch his head, you have less than 4/32 of an inch of tread left. If it doesn’t touch Abraham Lincoln’s head when you do the same test with a penny, there’s less than 2/32 of an inch of tread left.
These type of tires also affect stopping distances. Performance tires use softer materials that conform to the road surface better, providing more grip on dry pavement, but won’t grip as well as an all-season on wet pavement. Winter tires have tread compounds that stay pliable at low temperatures, offering better grip than all-season and summer tires, even if the pavement is dry.
Speed Really Does Kill
Speeding doesn’t just reduce reaction times, it also dramatically increases stopping distances. An average stop on a dry road takes 120 feet at 40 mph, 240 at 60 mph and 315 feet at 70 mph. On average, braking distances will double if the road is wet, and increase up to 10-fold if the road is icy.
When Brakes Don’t Prevent an Accident, Go to Merton Auto Body
When you need collision repairs, bring your car to Merton Auto Body. We’ve been in business over 70 years, and we’ve kept up with the times. Our staff is ASE certified, our shop is I-CAR Gold Class certified, and we have an estimating center to get work approved by your insurance company. We can get your vehicle looking and working as good as new as quickly as possible. Stop by our website or visit our Sussex, WI location for an estimate. We proudly service Waukesha County and the surrounding Lake Country areas including Oconomowoc, Delafield, Hartland, and Pewaukee.