Imagine the following scenario: You’re driving straight at high speed and you’re getting ready to make a right turn, instead of pushing the brake pedal, you pull up the parking brakes which slow the car down and you make your turn. Does this in fact shift some of that front heaviness towards the back and therefore easing the right turn?
It’s more accurate to say that it causes less weight shift than normal braking.
You’re still slowing the car down, and the car will try to rotate around its center of mass due to inertia, which means your front suspension will still compress, but less so. Mainly because the parking brake is weak relative to the normal brakes and so the car is not slowing down as rapidly.
It will not “ease the right turn” via weight-shift.
Now, what braking on the rears only does do is use up more of the total available traction on the rear tires, which makes it easier for them to break loose. This can be used to your advantage if you discover yourself understeering (say, on ice). A quick stab of the e-brake will make the back of the car rotate - but you should only do this if you know what you’re doing as it’s easy to lose control completely.
All that aside, especially on modern cars with 4-wheel disc brakes, the emergency brake is often a drum brake mounted inside of the rear rotor, and it has a very thin shoe on it. It’s good for only a few stops before it’s worn out and needs to be replaced, so as a general practice you should use it for parking and not braking.
Weight shift is the reason using only the rear brake on a motorcycle gives you almost no stopping power. Not only are you using only half your brakes, but using that brake takes weight off the rear wheel and you just skid through the intersection with a locked up rear wheel.
Weight shift is the reason that front wheels do the lion’s share of the stopping in a panic stop and why it’s so easy to spin the wheels on front wheel drive cars during acceleration.
Let the brake off before entering the turn or you’ll easily spin out.
In fact it’s a nifty way to do a quick 180 on purpose.
You’ll always have weight shift to the front as long as the center of gravity is higher than the ground.
Sounds like someone has been watching old black and white Moonshine bootlegger movies.
Frankly, just drive the vehicle like a normal person that way your brake lights will let the person behind you know that your slowing down .
Nope. It shifts the weight toward the front. Any braking shifts the weight toward the front. That’s why front discs are bigger than rear discs. They do most of the work.
Unless you’re driving an exotic. Most exotics now have an active spoiler in the rear that “goes vertical” when stopping, acting not only as an air dam but also pushing down on the rear to allow the rear tires to do more of the work.
Thank you for calling it a parking brake. Interesting intellectual question. On rally cars and similar they do use the modified “parking brake” to rotate the car, but on most normal cars the parking brake is not robust. Not really a good idea to use it while moving.
You can’t repeal the laws of physics. The weight shift to the front doesn’t really matter much which end that brakes. That said, a concept known as “brake anti-lift and anti-dive” comes into play to affect that a small amount.
You also will be very surprised if you miss releasing those parking brakes before you start turning. The car will spin. It takes a VERY practiced hand to use this technique to help the turn.
Rally, drift and gymkana cars USE this fact to help turn the car as well as using a driving technique known as the Scandinavian Flick.
You’re supposed to slow your vehicle before entering your turn, when it’s still traveling straight. Therefore, if you do it right, how you brake won’t affect how your vehicle behaves inside the turn, where you shouldn’t be braking at all, unless you have to make an emergency stop or you entered the turn traveling too fast.
Any braking shifts weiight forward, If you want to shift weight rearward, accelerate into the turn.
Remember riding your bike with rear and front brakes? If you really wanted to lay a long patch of rubber, you’d use the rear brake only. I remember when I was having trouble with a rear brake locking up on my Park Ave, I could be going 15 mph and the rear wheel would just skid for 10-15 feet not helping at all. I can’t comprehend how that could shift anything.
When riding mt bikes there’s a good deal of feel involved to how you apply the rear vs front brakes. The rear brake is where you start applying first usually. Too much front will cause the front wheel to skid, which is no good b/c you can’t steer. If you want to avoid the bike pitching forward during braking or going down steep hills you move your butt backwards so your body’s center of gravity is mostly over the rear wheel.
When I was a kid, I rode a bicycle with only a rear coaster brake. I got really good at doing those skidding stops where you also do a 180 degree turn.
That was an era before grownups made kids wear bicycle helmets and school crossing guards made kids walk their bicycles across intersections.
A bicycle’s weight, geometry, and distribution of braking forces are so unlike a car’s that I would rather contrast them than compare them in a discussion like this. Heck, even my motorcycle, (a v-twin metric cruiser) behaves nothing like a bicycle when braking.
You won’t see me trying to power slide any motor vehicle like I did a bicycle as a child, except maybe a golf cart, which only has rear brakes.
But the physics are the same. It is common to use a “bicycle model” to explain the vehicle dynamics of a car. That model is used more for steering and cornering dynamics because the braking physics are pretty simple by comparison.
It seems w/an automobile there’s still a fundamental difference between the effect of applying only the rear vs only the front brakes. If you apply only the rear brakes the car will pitch forward, but will never do an end-over. If you apply only the front brakes the car’s rear end could come up so fast it flips over the front; i.e. it does an end-over and lands on the roof.
GeorgeSanJose- How would you suggest applying just the front brakes? And what kind of tires would supply that much traction? And if you could generate that much force, how would the fact that the rear brakes were also applied matter? The rear tires would be off the ground quickly.
The reason rear car brakes don’t cause as much weight shift is because they can’t exert near the force as the front brakes. Apply rear brakes hard, weight shifts forward, rear tires skid, car doesn’t slow a lot. Apply front brakes hard, weight shifts forward, tires grip and slow the car much more effectively.
I will have to rely on your personal experiences, I have never had this occur with street vehicles or off road.
Agreed. I’ve never seen this happen to a car, even when locking the brakes, and I doubt it’s possible to flip a car forward unless you’re driving down a very steep incline. There just not enough upward momentum on the back end. Maybe an empty pickup truck could do this, but even it probably weighs too much.