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. 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. As long as the brake system can handle the extra heat generated. Slippery surfaces change that. 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. 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 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Jackie Lee Mowery Sent: Tuesday, December 04, 2001 9:59 PM To: [EMAIL PROTECTED] Subject: Re: OT: SUV's - was: Illegal Street Photography? whoa. Mafud is right about this one. First off, brakes do not stop anything other than the wheels turning. Tires stop vehicles through the action of friction against the road surface. Second, the size of the footprint is meaningless. All it means is that the weight of the vehicle is spread over that many more square inches (cm or whatever). Friction is determined by the weight (downward force of the mass) and the co-efficient of friction of the two surfaces. This is of course the maximum frictional force exerted by non-sliding surfaces (that tricky edge between braking and skidding. Once you start to slide the force of friction actually decreases. (hence the old adage about pumping the brakes) While the vehicle weight affects the braking power (friction) it also affects the momentum of the vehicle (for the same speeds heavier vehicles have more momentum), so it tends to cancel out leaving stopping distance pretty much directly proportional to speed. And like he says, feeling safer, SUV drivers tend to speed in iffy conditions. 4-wheel drive will get you into more trouble than it will get you out of. Hey, I have to feel I am at least occasionally using that physics minor I picked up in college. In search of the perfect image. It can hide, but it can't run. - 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 . ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com ********************************************************************** - 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 .
