Quote:
Originally Posted by qoncept
It's still absolutely wrong. Play with the calculator below. You'll see that when you increase the maximum available force you also increase the maximum static (rolling) friction. In other words, if your brakes are stronger, you can apply more force before you lock them up. It's a chain that starts at the pad and ends at the road.
It's right here, clear as day. Unsubbed.
http://www.ajdesigner.com/phpfrictio...imum_force.php
Example:
We'll make up a coefficient for brake pads on rotors since I reall have no idea.. lets say 0.8.
- Stock brakes apply 20 newtons of force, which gives us a max of 16 newtons of friction on the rotor. Tires on road is a coefficient of .9, and the 16 newtons we're applying gives us stopping force of 14.4 newtons.
- Megabrake applies 25 newtons of force. Same coefficient of .8 means the rotor sees 20 newtons of friction, and then the tire on the road sees 18 newtons of maximum static friction.
Of course, the friction required to stop a car increases exponentially. Same deal with power and acceleration. |
No, no, no. You're totally mixing up the equations. You shouldn't be adding the stopping force at the rotor to the stopping force of the tire on the road. That's like saying if you're towing a trailer the amount of force the tow vehicle can apply to the trailer is equal to the amount of force the two vehicle can apply to the road plus the amount of force the attachment point (hitch, chain, whatever) between the tow vehicle and trailer can sustain without braking. The reality is that the total force that can be applied isn't the sum, but the minimum of the two forces.
In this case, force applied to slow down a wheel doesn't change the amount of frictional force between the tire and the road. They're two different frictional forces. The only correlation is that the maximum braking force is the minimum of the two, not the sum.
Quote:
Originally Posted by qoncept
The examples I just posted (see the bold) say that the wheels lock up at 14.4 newtons in the stock example, 18 newtons in the upgraded brake example.
The number you're calculating is maximum static friction. Increase force, increase maximum static friction. Stronger brakes increase the threshold of friction between the road and the tire before locking up.
So no, you don't just lock up the brakes easier.
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You're using the equations 100% wrong.
First, if you want to see how much total force is being applied to the wheels from the brake pads you need to look at the amount of force being applied to them, the mu, the rotor speed and the diameter of the brake rotor. Just the mu and pressure isn't nearly enough.
Second, you simply can't apply more force to the rotor than the tires can to the road. Once the wheel locks the amount of braking force between the rotor and brake pad goes way down since the rotor speed is now 0. You can do all the math you want, but I'll give you a hint that the maximum amount of force you can apply through the rotor in a given situation is exactly the same as the maximum amount of force the tires can sustain without locking up.