I was making a tight U-Turn the other day in a parking lot, and I hypothesized that going a bit slower might have made it impossible for me to make the turn. To test the theory, I turned around again and made the same turn, but this time I went really slow. As I expected, I didn’t make the turn.
Is this an actual phenomenon. And, if so, does anyone know why this happens?
Thanks,
Heembo
probably because when you u-turn at speed, your tyres slip sideways due to the momentum in the direction away from the direction you’re facing when you’re making the u-turn…
or in other words, at slow speeds, your rear tyres just follow the front without a mind of their own…at high speeds, you lose a bit of the back-end going into a u-turn, enabling you to take the turn in a lesser radius…
here’s something i do often don’t try it at home warning go at a decently high speed, slam your brakes while simultaneously slamming the accelerator and pullin’ up the handbrake, turn your steering wheel to the extreme…if you get it right your car should do a 360 degree turn almost on the spot ( i.e. very small radius )…now try that at slow speeds…and you won’t be able to…
did i drive the point home ? 
I expect there is slippage between the rear wheels and the pavement at high speed which would result in a faster turn. If you go into a turn on ice and floor the accelerator (at least in a rear-wheel-drive car) your rear wheels will spin about the axis of the front wheel on the outside of the turn, allowing you to execute a 180-degree turn with virtually no forward movement. If you’re really good at winter driving, you learn to use techniques like this to maneuver in tight spaces. On pavement, the slippage would be less, but there would be a little–enough to make the radius of the turn a couple of feet shorter, I would think.
James Garner invented the “garner turn” used by law enforcement across the nation. He would back up at high speed, turn the front wheels slightly, causing the car to go into a skid, jerk the gearshift from reverse into drive, floor it, and the car would come out of the skid headed in the opposite direction at high speed in drive. It’s why you should never buy a used police car.
Does it matter if the car is front or rear wheel drive? Seems like the above conditions hold true for a front wheel drive car, but that the opposite would be true for a rear wheel drive car.
rear-wheel drive is actually much, much better for pulling rally-style turns. front-wheel drive cars tend to have understeer, whereas rear-wheel drive tend to oversteer. if you know what the hell you’re doing, you can do a heck of a lot more with rear-wheel drive, hence the reason lots of car nuts refer to front-wheel drive as “wrong wheel drive.”
Let me explain…basically slippage is more-or-less the key, as mentioned by the other posters. As you’re taking a sharp turn at a high speed, a front-wheel drive will have the tendency to go wide on the turn. A rear-whell will tend to follow the line much better. If you’re line isn’t tight enough, you can sharpen your turn and what will happen is the back will kick out a bit, and once the tires get traction again, you’ll be heading exactly where your nose is pointed. There are two basic ways to initiate this kind of oversteer: Lift-off oversteer and throttle-on oversteer. In the former, you lift your foot from the accelerator. This throws the weight of the car forward, your back lightens, and hence loses a bit of traction so you back swings around. In throttle-on oversteer (easier to control) you more-or-less hit the gas to make the tires spin faster than the ground moving underneath, and hence they lose their traction that way.
If you ever see those “power slides” on rally circuits, that’s basically extreme oversteer at work. The reason this doesn’t work with front-wheel drive cars should be fairly logical. With the power coming in the front, if you were to lose traction on those tires, well, you don’t have a set of tires to point you in the right direction when the traction kicks back in. Basically, you lose your pivot point.
Hope that makes some sense
Good answers so far.
I’d like to point out that oversteer is not impossible with a FWD car. It depends on the roadholding characteristics, but some FWD’s WILL oversteer (albeit not as dramatically) when you suddenly lift off the accelerator in a high speed, on-the-limit turn. I know my car does (Peugeot 306), and my last car (Peugeot 205) was notorious for doing just that.
And if all else fails, there’s always the handbrake to facilitate tight cornering. Works for both RWD and FWD, and the advantage is that when you release the handbrake again, the rear wheels will regain traction almost instantly. Power oversteer (that is: making the back end of a RWD break out by using the accelerator) is much harder to control, and especially unpredictable when doing it in an automatic car. A manual will give you better control, but it’s still a tricky manoeuver - especially when the car’s a powerful one. Almost anything with 150+ BHP will surprise a moderate driver by snapping around 180 degrees.