Interesting ideas, Dan. But, somebody educate me here, please! Way back in 1952, when I was wet behind the ears, I went off to a big building in Cambridge MA, where they fill skulls full of mush with facts and theories. One of the subjects I had to study was physics. I must have passed it, because they let me out of the place, and even gave me a piece of parchment to show I'd been there. In physics we learned that stopping a wheeled vehicle required only that the wheels be prevented from turning, and that the wheels grip the road surface well enough to avoid slipping. All that was required was that the brakes be able to lock up the wheels, and that the tires have an adequate coefficient of friction. The optimum stopping distance requires that the brakes do not quite lock up the wheels, as the rolling coefficient of friction is higher than the sliding coefficient of friction. A very skilled driver knows just how hard to push the pedal to stop in the shortest distance. Most of us, myself included, only jam down the pedal, and hope that the coefficient of sliding friction is good enough. (Modern ABS brakes attempt to duplicate the very skilled driver by moderating the braking force to prevent wheel lockup.) If the tires won't grip the road well enough, something is wrong with the tires. Better tires are worth buying, for that reason alone. (I recommend the Tire Rack stores web site for information on what tires stop better). I just buy Michelin tires. Coefficient of friction gives the relationship between the weight of the car and the deceleration force. In other words, the weight of the car falls out of the equation, meaning a heavy car will stop just as short as a light car, ignoring some minor factors. OK, the minor factors are: In a heavier car, more heat will be generated at the tire/road interface, and if the contact patch isn't larger, the tires will overheat quicker on the heavier car. A mitigating fact is that since almost all passenger cars use the same tire pressure (30 to 35 PSI), the contact patch also automatically adjusts for the car's weight, thus reducing or eliminating the heat difference. If this doesn't sound right to you, visualize what happens when you add weight to a wheel - the tire flattens out so the contact patch grows - what sets the relationship? Right, the pressure in the tire. A tire with 30 PSI inside it has a weight supporting ability given by the contact patch size times 30 PSI. In our cars, where the weight on the front wheels gets up to around 1600 pounds per wheel (Guessing here) during a fast stop, the contact patch grows to 53 square inches. In the little modern car, which let say weighs half as much, the contact patch will grow to 27 square inches, or half that size, so the heat per square inch applied to the rubber is exactly the same. If a car is driven with brakes that cannot lock up the wheels, something is wrong with it, or the driver is too weak to press the pedal hard enough. If all the wheels don't lock up at the same pressure on the pedal, something is wrong with the balance front to back or side to side, but the car will still stop, although not straight in its lane. Since all Imperials built since 1951 have power brakes, I doubt anyone has trouble pushing the pedal hard enough on a car that is working right. This all brings me to the conclusion, that (except for cars in bad condition, repeated stop situations, or looooong downgrades where the driver doesn't downshift, thus causing the drums to overheat and expand, also lowering the linings coefficient of friction to the drum due to overheating,) there is no significant difference in stopping ability between disc brakes and drum brakes. I have a feeling I'm missing something here - so please take me seriously and tell me where I'm wrong. Thanks, Dick Benjamin -----Original Message----- From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of dansgarage@xxxxxxxxxxxx Hi All.....I know I know, "to convert or not to convert" has been kicked around LOTS on this list but I have had a number of close calls, regarding braking distances, when on the interstates here in southern California. As anyone who travels these Interstates knows its almost impossible to leave a 'safe' stopping distance beween your (Imperial) vehicle and the ones ahead of you since either 3 people try and move into that space or you find out real quick that the other (newer) cars can stop in MUCH shorter distances than you can! I have heard many discussions about changing to front disc's and whether or not its actually going to make a big enough difference to try it. ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. 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