Leaning: street motos vs. mountain bikes

Hi, Lee.
I just went through your book, and I have a question. I was wondering why motorcycle road racers always get off their seats to the inside (trying to keep the bike vertical) in corners, but mountain bikers do the opposite?

Hi Eric.

Excellent question, Grasshopper.

Team Honda racer Jake Zemke. www.hondaredriders.com

Why it works on a street motorcycle

Less bike lean. At any given speed and turn radius, there’s one lean angle that correctly balances gravity and turning Gs. This is the angle between the contact patch of the tires and the center of mass for the bike/rider. When you lean your body into a turn, you have to lean your motorcycle less. This is good because:

More ground clearance. Pavement traction is abundant and consistent. With all that grip, you can lean a moto far enough to scrape parts on the ground. (I’ve done it: Frequently on my Honda VFR800, and once on a BMW R1150RT touring bike in the Italian Dolomites. What a day!)

Better traction. You put more meat on the ground with a reduced lean. Also, once you get past about 45 degrees of lean, the tire starts acting like a circular scrub brush, whicis more about scrubbing than gripping.

More control. Advanced riders use their knees to sense where they are and to unweight the back end when they want the rear end to braaap around. (I’ve never done that — not on the road anyway.)

The sun is setting, and Bobbi Watt is railing this gravel turn. Nice.

Why it doesn’t work on a mountain bike

Sketchy traction. MTBs don’t get the kind of traction road motos do. When your tires can slip at any second, you want to stay balanced above the edges of your tires. If you lean farther than your bike (like a road racer or Bicycling Magazine reader) and your tires slip, goodbye. If you stay above the edges and your tires slip, that’s called drifting. Cool!

Less camber thrust. The more you lean your bike, the more your tires generate “camber thrust,” which is like rolling an ice cream cone — it turns on its own. This is the safe way to turn a bike, especially on dirt. The less you lean the bike, the more you have to steer. When you steer your front wheel through dirt, you plow it through all those tiny particles like a rudder. That’s so random — better hope your tire deflects where you want it to.

Summary: In most situations, lean your bike more than your body. You’ll corner faster and tighter, with more control.

But you can still say BRAAAP!

Left to right: Sketchy to sweet. It was so hard to get Bobbi to lean her body inside the turn. She knows better.
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