Quote:
Originally Posted by strat61caster
That diagram implies that your front tires (doing all the turning) has imparted some acceleration in the forward direction, not true.
From a pure free body diagram physics perspective: It's the forward facing vector has a slight angle to it as if the rear tires are slipping and providing an additional lateral cornering force. This means that less steering angle is required to generate the proper line through the corner.
Less steering angle = less rolling resistance as the tires are pointed straighter = more speed.
I'm not terribly happy with this diagram, but for a half hour in powerpoint it should get the conversation started nicely. Lots of things I'm not happy with, mainly I sized my vectors poorly and inconsistently to get the point across.
Consider this a draft and if I get bored sometime later I might make it correctly so that oversteer+ is actually comparable to the neutral turn.
I also believe Mike was using a more 'feel based' learning tool to convey the concept, not a hard free body diagram, but might as well go overboard.
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I can save you some time. Take the neutral drawing, and rotate it 5 degrees CCW for understeer, and CW for oversteer. Take the x components of the front and rear force vectors, and understeer will be destructive (subtractive), while the oversteer will be constructive (additive).
If you really want to go overboard, you shorten the front vector for understeer, and shorten the rear vector for oversteer (kinetic vs static friction). The net X component will still have the same type of difference as above. For the sake of the exercise, we assume that the tire has an equal amount of longitudinal grip as lateral grip.