Can you turn a motorbike by just leaning?

Question

Right, imagine you are on a motorbike, going straight forwards, 100mph. Now imagine the steering is WELDED forwards. You can not turn the front wheel at all, in any way.

If you leaned to the left or right, would it be possible to slowely turn the motorbike as it sped along? Or would the fact the wheel is welded forwards means the bike would simply either stay going forwards, or if you leaned enough, you'd topple over?

Answer 1

The short answer: Yes...you can. It's hard to eek out much more than sweeping arcs bcs...you're taking out the most significant factor on steering...the steering head! It's by far more effective to use countersteering to swing the bike into the right geometry.

But you definitely can. The effect can be even more dramatic if you don't restrict the speed to 100mph but rather allow the rider to decelerate/accelerate a little--allowing him/her to accentuate the balance shifts. The reason why is because of wheel geometry. When leant over, your weight will create the imbalance necessary to start the bike leaning over as well. Once the bike is leaning over as well, the wheel geometry begins to have an effect, and sets the bike on an arced path.

Specifically, motorcycle tires are rounded, and the front tires are always more rounded than the rear tires. The fact that the tires are rounded in cross-section and not flat like car tires facilitates turning while leant over. And the fact that the front tire is more extremely rounded gives the front more of a tendency to turn while leant over, giving the bike an effect where the front of the bike tends to lead the back of the bike into a turn, maintaining proper orientation.

As for the details of why a rounded tire works--With a rounded tire, the contact patch travels different circumfrences depending on whether the wheel is standing straight up, or leant over. The circumfrence of the widest point (traced down the centerline of the tire) is going to be larger than one traced around any other path--say for example a path traced 2" to the side of the centerline. When you're leant over, some of your contact patch is tracing a path closer to centerline, and some of your contact patch is tracing a path further from the centerline. The principles of geometry tell you that in order to add up to reality, the path the contact patch traces on the ground will tend to be arced so that the outside of the contact patch (the area of the contact patch further out on the wheel) can trace a smaller circumfrence along the road than the inner side of the contact patch (the area of the contact patch closer to the centerline of the wheel).

You can simplify this observation by approximating the curved profile of a tire with a chamfered profile instead. Take a cone and slice off a thin section from the end of the cone such that you get a round object with a chamfered side. Stand the cone-section on it's chamfered side and roll it on the ground...it rolls in an arced path. Stick a few chamfered cone-sections together put a and a bike frame in between. Congratulations, you now have a bike. The answer would be completely different if you had flat tires on the bike like a car's tire. Is it effective? Not really. By far, the most effective way to steer a bike, whether slow or fast is with countersteering and leaning. Anyone who tells you differently is misleading you.

Answer 2

Strech and bikernoj are clueless, and most others who responded obviously know nothing more of motorcycles than what they can guess or figure out by looking at them.

Steering is NOT accomplished by leaning (one's self) on a bike, at low or high speeds. Steering at high speeds is accomplished by counter steering. Believe it or not, turning the steering to the left will lean the bike right, and vise-versa. Those that think steering is only "enhanced" by counter steering don't know how to ride. When one "leans on a bike" they are holding onto the steering and, because of the pull their body creates on the bars because of the lean, they are counter steering the bike and don't realize it. In reality, steering is accomplished by counter steering, and enhanced by leaning (meaning shifting your weight). Yes, the bike must lean to turn, but how that lean is accomplishied is obviously a mystery to most, even those who have read the right books.

When I first started riding, I thought I was steering by leaning only (even though I was counter steering without realizing it). Once I was taught the proper technique, which is to KNOWINGLY counter steer, bends that seemed like a big deal to take at 50mph could now be taken effortlessly at 70mph, without the bike even feeling like it was close to the limits. Those that think they've learned so much from watching Moto GP should notice that when the riders are leaning over to the right, their front wheel can CLEARLY be seen pointing to the left.

The point? It's impossible to steer WITHOUT counter steering. Those that think it's by lean only are counter steering and don't know it, and if they consciously started counter steering they might actually become a decent rider.

Answer 3

Yes, you could turn because a motorcycle MUST lean to turn. It wouldn't handle well or turn as sharp, but it would turn.

To understand why, you need to know the concept of "coning" that happens with motorcycle tires. Car tires are square, because as they turn the tire remains square to the road. Motorcycle tires have a rounded profile, and as the bike leans the effective circumference of the tire decreases.

To see this, take a tapered plastic cup and lay it on its side. Notice how the opening is bigger than the base, and try to picture the profile of a motorcycle tire being the same. Now roll the cup.

Notice how the cup rolled in a circle instead of going straight? that's the exact concept behind how motorcycles turn, and why they must lean to do so.

This explanation is given in much better detail in a book titled "Proficient Motorcycling" and should be a must read for anyone who rides or is thinking about riding.

Answer 4

for the hypothetical question, yes. here is why: a wheel is round, and the tire is tubular. when the tire is rolling vertical, the part of the tire touching the road is straight. if you lean the tire ot one side, the part of the tire touching the ground is curved. you will turn in an arc the same diameter as the curved patch of the tire. that is also why inline skates can steer. snow skis follow the same principle. a good skiier dosent throw much snow up in the air when he turns. the weight of the body over the skis in the snow makes them bend. lean the bent ski over on its side and it will follow the bend to carve an arc in the snow. that is why skiiers refer to it an an arced turn. i hope this helps.

Answer 5

First off you wouldn't ride a motorcycle that has the steering welded..... but you do have to lean into a turn be it right or left...

Answer 6

no.its already been proven. with a second set of handlebars welded to the frame. without the ability to change the direction of the wheel , even slightly, the bike will continue straight on.

Answer 7

If you lean , the bike will turn in that direction, however this will not work at very slow speeds and if you lean far enough I guess you would topple over.

Answer 8

Yes, once you are going faster than ABOUT 20 mph, you steer a bike by leaning, or shifting your weight, or a combo of....NEVER by turning the front end.
How do I know?
I've been riding street bikes for over 30 years now.

Answer 9

No, you could lean the bike to turn.

Answer 10

if you leaned past 3:00 or 9:00 to the right or left you would fall over.....otherwise you could gently lean and slightly turn it.