Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: $Revision: 1.6.2.14 $; site siemens.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!siemens!bhs From: bhs@siemens.UUCP Newsgroups: net.auto Subject: Re: How to turn a Saab? Message-ID: <25300042@siemens.UUCP> Date: Fri, 7-Jun-85 10:06:00 EDT Article-I.D.: siemens.25300042 Posted: Fri Jun 7 10:06:00 1985 Date-Received: Sat, 8-Jun-85 02:46:34 EDT References: <13200026@hpfcla.UUCP> Lines: 44 Nf-ID: #R:hpfcla:-1320002600:siemens:25300042:000:2354 Nf-From: siemens!bhs Jun 7 10:06:00 1985 Rob: There seem to be at least two accepted ways of turning a Saab. The easier one of the two, which both work at a point close to the performance limit, which is what you are worrying about, is to snap your foot of the throttle suddenly. This will typically cause your car to suddenly switch from understeer to oversteer in such a way that the car can actually hang it's tail out, at which point you step on it again. The second way is in fact a tricky variation on the first. What you have to learn is to accelerate and brake at the same time. In order to understand this one, which is favored by rally drivers, you must look at the force vectors on your tires in this maneuver. Your tire can handle a lateral acceleration of only a certain amount. This lateral acceleration can be either centrifugal force from cornering (centripetal force for the purists ), acceleration, or braking, or any combination of the above. Thus, if you imagine yourself whaling around a turn, all four wheels will be subjected to a certain amount of cornering force. If you now accelerate, your front wheels will, in addition, be subject to a second force caused by the torque of the wheels. Your rear wheels will not have this vector of force applied to them. If you now step on your brakes, all four wheels will suddenly have this retarding force applied to them. However, remember that your front wheels have the other accelerative force on them too- a force going the other way. The trick is to apply gas and brakes in such a way that the two forces counteract and cancel each other- leaving a greater net force on the rear wheels, which will break out sooner than the front wheels. This technique suddenly exposes the importance of front- rear wheel braking power balance, which is why pro racers will try to have a variable regulating valve for the brake system. Tricky? Another application of this theory will explain why rear wheel drive cars are easier tturned by stepping on the throttle- the torque on the rear wheels will break off the adhesion. BTW: I believe that Saab parking brakes work on the FRONT wheels, not the rear wheels as in most cars. The gas and brake method is now quite accepted, however it is a new method. It is believed that as late as 1967 only 7 people in the world knew how to do it. Bernard H. Schwab Siemens RTL, Princeton, NJ