Once on a trip to Maui, we took a day trip to the Haleakala Volcano. This is a road that goes from Sea level to over 10,000 feet in about 27 miles, with plenty of pedaling on and off the brakes. I noticed several signs that suggested to downshift instead of using my brakes and I thought to myself, “that would be a great blog post!”
Photo Credit: JoshBerglund19 via Compfight cc
The reason that you want to downshift is to protect the brakes. When your brakes are applied, they create friction, and this friction is what slows the vehicle down. But friction also creates heat, and too much heat will damage the brakes. Too much heat can also make brakes completely fail. Brake failure happens when brake fluid gets too hot and starts to boil. When brake fluid boils, brake pedal fade will occur, or complete brake failure can happen while driving downhill.
A vehicle’s downhill speed will increase due to gravity. Heavier use of the vehicle’s brakes is needed in order to slow down the vehicle’s progress. Under heavy braking, brake fade can occur. Brake fade is a result of overheating and reduces friction between the brake pads and discs. When brake fade happens, it reduces the effectiveness of the brakes, which is dangerous and often more common in larger vehicles.
The good news is that you can descend down most any hill without ever using your brakes. This is done by a method of “downshifting,” or selecting a lower gear. This method uses the vehicle’s drivetrain to slow the vehicle. Large trucks have been using the downshifting technique for years.
How To “Engine Brake”
If your car has a manual 5-speed transmission, you would typically use 3rd gear if you want to descend a hill around a 40mph speed limit. Most of the time, that will help you maintain your speed, and you may even have to accelerate a few times. If you are going too fast, then a 5 second push of the pedal will slow you down without overheating the brakes. When you downshift into a lower gear, the brakes will have a chance to cool before you use them again. If you hold onto the brakes by riding the pedal for an extended period, the brakes will overheat and will become damaged. When you get to the bottom of the hill, simply put the vehicle back into drive and it will go back to computer-controlled shifting for optimum fuel economy.
Several types of vehicles, like the Acura MDX and BMW x5, come with sport modes that give you enhanced control over the vehicle’s transmission. Most Automatic Volkswagens use a tiptronic transmission switch. When you shift into that mode, it allows you to select the gear you want like a manual transmission without a clutch pedal to push.
If you have questions about downshifting and using the engine to help slow you down hills, contact one of our experienced technicians at Central Avenue Automotive. You can give us a call at (253) 854-6762, or schedule an appointment using our convenient online appointment booking service. You can also come into our repair shop, located at 1514 Central Ave. Kent, Washington 98032.
