From: "Kent Gittings" <[EMAIL PROTECTED]> > I agree with most of your comments. And it is the tire that actually stops > the vehicle. The brake system is just to remove the excess heat from this > action.
No. In addition to dissipating the heat of breaking, (same as the energy required to stop the vehicle), the break system also supplies the force necessary to slow and stop the rotation of the axel which is connected to the wheel which is connected to the tire. Yes, the tire stops the vehicle. > However a vehicle with wider tires, assuming the same brand/model > and coefficient of friction, will stop in a shorter distance than the same > vehicle with narrower tires. No. If other things are all things are the same, including the coefficient of friction, the width of the tire is irrelavent. Stoping distance is the same. The only thing that counts is the force that can be applied and the coefficient of friction. > As long as the brake system can handle the > extra heat generated. No extra heat will be generated. The heat generated is exactly equal to the energy of the vehicle before breaking and is 1/2*m*v^2. There is an additional term if the road is not level. Temperature will vary with rate of heat input and rate of heat dissipation (which will vary with temperature, airflow, conductance etc.) > Slippery surfaces change that. Slippery surfaces change the coefficient of friction. Nothing changes the energy dissipated in stopping a vehicle. > And while things like 4WD and AWD won't allow you to stop any better under > slippery conditions the increase in control will allow a GOOD driver to get > out of situations a normal driver would not. True. > For instance I was driving with > my wife one cold non snowy day in a 92 Ford Explorer (shift on the fly 4x4 > not AWD) and I crested a rise to a downhill section of a crowned 2 lane back > country road I'd been on many times. Park land on both sides with mature > trees right up to the near edges of the road with no guard rails or fencing. > Doing about 50-60 MPH I saw something ahead that looked bad. In this case > some cars had crashed due to a thin coating of ice that completely covered > the road for a short distance. At this speed there was no way to stop in > time. At least they weren't blocking the road. So rather than trying to > stop, first my wife reached up and slapped the 4x4 switch on the dash, while > I accelerated slightly and steered to go over the left side of the road > because I could see the ice covered a shorter distance on that side. Once > past the ice we stopped and rendered assistance. While another car came down > the hill, tried to stop, and went into the trees. Why did I speed up instead > of trying to slow down? Because in the case of a 4x4 system with a fully > locked front hub arraignment the only advantage you have and the only > scenario that gives you maximum control is when all the wheels are > accelerating. > > Here is the first question on a test to see if you are automatically in the > 95% of bad drivers (we call them pointers not drivers). > When you are stopped or at a low speed making a turn do you find yourself > using the opposite hand from the turn, putting it inside the steering wheel > spokes and grabbing the wheel and pulling the wheel down to start the turn > before using your other hand to continue turning the wheel? > Bonus points if you can tell me both reasons why you should never do this. > At a driving school like Bondurant you only get to do this once then you get > your money back and are told to leave the premises. > Kent Gittings - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
