how’s that for a tongue twister? 
i was on the bus to work this morning and passed an automotive shop advertising wheels for one price and tires for another, what’s the difference (if any)?
also, what is the difference (if any) between 4-wheel-drive and all-wheel-drive?
and finally, whatever happened to those cars that had that all-wheels-can-turn system to help ease parallel parking?
2)http://boards.straightdope.com/sdmb/showthread.php?threadid=62671
3)Still too expensive and not yet reliable/durable enough to be practical for ordinary vehicles.
damn. should be:
The late 80s Honda Prelude and Mazda 626 (European names, of course, the American counterparts may be named differently) both had versions with 4WS (Four Wheel Steering). At high speeds, the rear wheels would steer in the same direction as the front wheels, causing the car to switch lanes more gently. At lower speeds (say, parking), the rear wheels would steer in the opposite direction, thereby increasing the manoeuverability of the car in small spaces.
While this facilitated parallel parking, it by no means meant that the car could just slide in laterally. A system like that requires the wheels to be able to twist completely sideways. Some off road vehicles have that possibility, but it requires a lot of space and it is expensive to make and maintain.
Here’s some more background on the technical history of 4WS, and why it’s not being used anymore today.
Incidently, my car (peugeot 306) has an active self-steering rear axle that makes it really fast through corners. Doesn’t do anything for parking agility though.
Here’s a page with a few photos of the 4WS system in action on a Mazda 626.
My Dad drove a car-hauling truck back when 4WS came out. There were a LOT of accidents driving the vehicles up onto the trucks, the cars with 4WS turned differently from standard cars at those low speeds and they were always getting driven partially off the ramps. Eventually they started disabling the rear wheel steering until they got them off the trucks.
4WS is coming back for big trucks and SUVs to help them park. I don’t think the highway driving mode is wanted or needed, but the ability to park those monsters is becoming more of an issue.