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[cycleworld.com] - How Motorcycles Turn: Camber Thrust
Motorcycles are not steered in the same manner as a car, but why is that? Two words: camber thrust. What is it, and how does it make a motorcycle turn?
Click here to view on their site. ![]() Kevin Cameron has been writing about motorcycles for nearly 50 years, first for Cycle magazine and, since 1992, for Cycle World. (Robert Martin/)Camber thrust. What is it? How does it work? I remember how mystified I was when I first encountered this idea: that a tire could generate a cornering side thrust just by cambering—that is, leaning as motorcycles do—without being steered as car tires are. When the motorcycle is upright and you want to turn, the first step is to lean the bike into the turn. To do this, you steer the tires out from under the bike by very slightly turning the bars opposite to the turn. This steers first the front wheel, and then the rear wheel out from under the bike’s center of mass, causing it to fall over into the turn. This is countersteering. What stops it from falling completely over? Two things:
Related: Body Positioning And Steering Techniques ![]() The torque resulting from the outside of a tire’s footprint trying to roll farther than the inside is camber thrust. (KTM/)This means that the outside of the footprint tries to roll farther than the inside. The result is a torque on the footprint, tending to steer it into the turn. I went to one of the less secretive tire engineers I knew, recited this description like a schoolboy, then said, “This is camber thrust. True or false?” “True,” the engineer said. When you begin a turn by countersteering (making the motorcycle fall over into the turn by countersteering its wheels out from under it), the tire circumference at the beginning of countersteering is the same at both edges of the tire footprint. No camber means no camber thrust! Related: How to Countersteer on a Motorcycle Correctly So during initial countersteering, the front tire steers just like a car tire: by slip angle. It is only as lean (camber) angle increases that the tire circumference becomes different on the two sides of the tire footprint. That difference distorts the tire footprint, rotating (steering) it into the turn. The side force that “steering” of the footprint generates is camber thrust. Car tires don’t do this because: One, tire camber angles are always very small. And two, modern belted radial auto tires have nearly constant circumference from one side of the footprint to the other. A nicely setup motorcycle just lies there in a turn of constant radius, turning with all forces in balance. You can choose to adjust the angle of lean, or even to lift and accelerate by adding your two cents to this balance, tipping it in the direction you want.
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Thread | Thread Starter | Forum | Replies | Last Post |
[motorcycle.com] - Evans Off Camber – Motorcycles and their Riders | Ninjette Newsbot | Motorcycling News | 0 | November 3rd, 2014 01:20 PM |
[motorcyclistonline] - In Thrust We Trust | Ninjette Newsbot | Motorcycling News | 0 | May 27th, 2014 08:30 PM |
[sportrider - tech] - Ask The Geek: Thrust, Horsepower And Rear Tire Handling | Ninjette Newsbot | Motorcycling News | 0 | April 13th, 2010 04:00 AM |
[MotoGP News] - World Superbike, Round 3: Thrust And Parry | Ninjette Newsbot | Motorcycling News | 0 | April 17th, 2009 11:20 AM |
[sportrider - tech] - Ask The Geek: Thrust, Horsepower And Rear Tire Handling | Ninjette Newsbot | Motorcycling News | 0 | January 16th, 2009 01:23 PM |
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