I've used the car's spare jack to change tires before; even with a socket wrench it takes forever to raise and lower the car. I was hoping someone would already have a standard hydraulic jack with height xx" and tell me that it was good enough (or not) and save me the trouble of lifting the car.Wagoneer wouldn't your vehicle's jack be a good indicator of how much you'd need? I'd think just about any commercially available floor jack would have enough lift. As important is one when in the fully retracted position would fit under the vehicle.
Then you probably need something that handles 18-20 inches. Jacks are cheap, it doesnt hurt to buy more jacking capability than you need?Kill me? I wouldn't go under the car when it is supported only by the emergency jack! It's for tire changes. As long as you change the tire efficiently, the chance of it collapsing with nothing mounted on the hub is pretty slim.
I already have the cheap Craftsman 2.5 ton trolley jack, and I can say that it doesn't have enough lift to get a tire off the ground. However, I think it has only about a 15" lift.