Originally Posted by Patrick Olsen
I'm trying to wrap my brain around this one. It seems to me that a very tight rear diff would cause power-on understeer, not oversteer.
Most people don't experience this. If I were to venture a guess as to the mechanics behind it, it would be that because the unladen wheel must spin at the same rate as the outside wheel, the slip angle on the unladen wheel is increased to a point where it is not contributing very much to the cornering force, causing a net reduction in rear grip.
Think of your 3 wheeler going on a circle in dirt. Inside rear just spins at the rate of the outside wheel.
Any way you slice it, it would make sense for wheels sharing an axle that maximum grip will only be achieved if that axle is traveling straight, since to turn that axle is to ask one or the other to turn slower or faster than the pavement is moving by them.