: why are you not able to turn the steering wheel far when going at high speed?


Hi guys, i’ve noticed in racing games and in real life that the faster you go the less you are able to turn the steering wheel, why is this?

In: Physics

Basic answer is this force = mass * acceleration. Each of these components has a direction vector as a property. If a vehicle with a certain mass is going a certain acceleration, you need greater force to change the vector of direction. This part of the principles of inertia. It takes more force to stop a fast/heavy object and is a similar reason why it’s so difficult to maneuver a space craft in space.

You *can* turn the steering wheel far, it’s just a really bad idea. Note: not counting fancy stuff like speed-adaptive steering.

Your tires have a finite amount of grip. If they exceed that, they skid. The amount of force the steering tires need to apply depends on two things: how fast you’re going and how tight you’re turning. If you’re going slow, you can turn the wheels all the way and they’ve still got plenty of grip and it’s all fine. As you go faster and faster, the wheels will start to skid at smaller and smaller steering angles. If you try to turn them farther than that, they’ll skid (and possibly roll the car if you keep going). So you automatically limit how far you turn the wheel at high speed because you’re generating uncomfortably high accelerations on you, the driver, and your tires start to squeal.

Mechanically, there’s nothing preventing you from going hardover on the steering wheel at 90 mph. DO NOT DO THIS! It will take a lot of force, because the counterforce on the wheels is a lot higher, but you can do it. The wheels will skid, the car will probably spin, it might roll, etc. But the wheels will turn all the way.

I think I’m misunderstanding the question.

The actual range of motion of the wheel will always be the same (distance between the rackstops) but can be electronically changed with modern power steering products. I know bmw had one were less input was required at lower speeds to make parking easier.

But the wheel won’t have less rotations at higher speed.

I’m racing games you might feel like you’re getting less steering because you are understeering when you’ve exceeded the available traction on the tire.

Two questions: why shouldn’t you, and why can’t you.

First, why shouldn’t you? Because you will crash your car, either by skidding or rolling. The car has a lot of momentum trying to move it forward and if you ask the tires so change direction too much and too quickly, they won’t be able to.

Secondly, why can’t you? Well, you can but it’s just harder. And it’s harder because cars are specifically designed to make it harder.

Here’s a mini-history of power steering. In the beginning there was no power steering. The steering wheel was directly connected to the wheels, and it was quite hard to steer. When maneuvering at slow speeds where you wanted to turn the wheels a lot, it was really hard. You needed quite a lot of strength.

Then came power steering. When you turned the steering wheel, the car would detect it and help you turn. It became much easier to steer than before, particularly when you wanted to turn the wheels a lot.

However there was a problem at high speeds. It was so easy to turn that when to turned the wheel just a little bit, like you want at high speed, it felt like the steering wheel was just floating: there wasn’t enough control.

So they made adaptive power steering (or various other phrases for the same thing). It was designed so that at low speeds it would help you turn the steering wheel a lot, to allow you to maneuver easily, and at high speeds it would hardly help at all so you felt like you had control, and didn’t turn the wheels too much by mistake.

You probably can, but you most certainly shouldn’t at high speeds.
At high speeds the momentum of the car in the forward direction is very large so even if you manage to turn the wheels and turn the car, the momentum will carry it in the same direction (which is now sideways) and probably tip and roll your car.

Thanks guys for all of the answers!

The simplest answer is that you don’t really need to – when you are driving fast you only need to make tiny adjustments to the wheel – as a tiny adjustment made over a long distance will result in a pretty big end result.

If you turn the steering wheel right to its full extent, this will allow most cars to turn tight enough to do a full circle in less than 10m.
If you were travelling at 100kph/60mph, that is equivalent to just below 28 meters per second. So full steering lock at motorway speed would result in your car driving a complete circle in about 0.035 seconds.

Or, more realistically if you were to wrench the steering wheel to the side on the motorway, you would very suddenly lurch off to the side, probably lose grip and slide, and crash spectacularly – all you actually need to keep yourself driving along the smooth curves of a motorway is tiny steering inputs.

Cars do actually help us do this naturally – when driving along the forward motion of a car will want to keep the wheels reasonably straight (as turning them creates friction against the road) and this will cause the wheels to return from steering hard in one direction to fairly straight. This is amplified at speed, so the car will actually hold itself fairly straight for you.