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Mastering The Throttle

by by David L. Hough

More than a few riders have spit themselves into the landscape trying to negotiate tight turns. The official police accident reports almost always list "excessive speed" as the cause. Sure, most of today's big road rockets are seductively powerful, but actual speed entering a corner is only part of the equation. Are your tires at the correct pressures? Are they warmed up? Is your suspension set for the load? Most importantly, when do you roll off the throttle and when do you roll on during a corner? How and when you roll on�or off�the throttle has a lot to do with whether you make it around the corner, or end up picking your chin out of the dirt.

Back in the days when I was teaching motorcycle classes, the time came to get recertified to teach the "new" MSF curricula, which introduced the now-familiar "slow, look, lean & roll" cornering sequence. I really rebelled against the idea of teaching novice riders to roll on the throttle as they leaned over into corners. Up to that point I'd believed in decelerating towards the center of the turn on a trailing throttle, making a quick turn, and accelerating away from the apex. That technique allows a quicker, shorter turn at a slower speed. And it's still an acceptable technique for bikes with limited cornering clearance, "cruiser" ergonomics, or heavy loads.

The chief instructors eventually wore down my resistance to the concept of getting on the gas earlier in the turn. They talked about things like "stabilizing the suspension", "managing traction", and "smoother lines". And when that didn't convince me, they suggested that I'd teach the party line or else. While we were learning how to coach the new exercises, I gradually figured out that rolling on the throttle as you lean the bike does have some theoretical advantages. But if I was going to teach it, I needed to see if the theories actually worked, or were just more officious techno-wacky. As I tried out the concept in my real-world commuting, I verified that rolling on the throttle in corners does what the chiefs had promised.

So, ever since I got dragged kicking and mumbling into better throttle control, I've been preaching it myself. The technique is to smoothly roll on a little throttle as you lean the bike over, and continue to ease on the gas all the way through the corner. 

Rolling on the gas as the bike is leaned over accomplishes several things. First, it smoothes out the off-on throttle wobble at mid-turn. Second, it keeps the bike up on the suspension and the weight better shared between the wheels. Third, it helps equalize and stabilize traction. Put it all together, and it helps achieve a smoother, more predictable cornering line.

Smoothing Out The Wobbles

Many riders assume that bikes just wobble at mid-corner. One reason for a wobble is a transition from brakes to throttle. If you are decelerating towards the apex on a trailing throttle (as in Figure 1), then you need to get back on the gas as soon as the bike is turned. And that transition from deceleration to acceleration while leaned over is very difficult to pull off without a big wobble.

Be aware that rear wheel thrust or braking has an effect on both balance and steering. After all, when the bike is leaned over, the tire contact rings are off center from the bike. So, accelerating or braking will pull or push the bike on that side. 

While we're thinking about the relative position of the tire contact rings, let's also observe that the size of the contact rings shrink slightly in diameter as the tire leans over. The maximum diameter of a tire is at the center of the tread. Out towards the sidewall, the tire is smaller in diameter. And a smaller-diameter tire will need to turn faster to maintain the same bike speed. 

The point is, if you try to lean the bike over with a steady throttle, the bike will actually decelerate to match engine revs. Rolling on the throttle slightly while leaning over keeps the engine pulling to help maintain bike speed.

One advantage of today's wide oval tires is that speed will be more constant as the bike leans over. But there is also the disadvantage of the push-pull being farther from the bike centerline than with narrower tires. That's one reason why hanging off in corners has a greater effect on a sports bike with wide tires.

Up On The Suspension

With most motorcycles, rolling on some throttle lifts the bike up on the suspension. It's most obvious with non-paralever shaft-drive bikes. On chain or belt drive bikes, it may seem that the rear end squats under acceleration, because the front end is obviously rising. But almost all motorcycles will jack up both ends during acceleration, and squat on deceleration. One exception is a parallelogram rear end that resists either jacking or squatting, such as the BMW Paralever � system.

Lifting the bike up higher on the suspension not only improves leanover clearance, but also helps absorb bumps. Remember, on a level road, the bumps don't lean over--just the bike. The farther over the bike leans, the less effective the same suspension travel. For example, let's say your bike has 6 inches of suspension travel, and you've got it set up for 2 inches of sag. That leaves 4 inches of compression to absorb a bump, right? Well, at a 30 degree lean, that 4 inches of travel will theoretically absorb a 3.3 in. bump, and at 45 degrees, maybe 2.8 in. 

What's not so apparent is that at big lean angles, bumps force the wheel sideways as well as compressing the suspension in line with the bike, and that rolls (leans) the bike even farther, reducing leanover clearance.

Weight Shift

Rolling on or off the throttle also shifts weight from one tire to the other. Consider a straight-line wheelie, where the rider rolls on enough power to lift the front wheel off the surface. We tend to gawk at that front tire waving impressively in the air, and forget what's happened back at the rear. During a wheelie, all of the weight of the bike and rider has been "shifted" back to the rear wheel.

Braking will cause weight shift from rear to front. Really hard braking can lift the rear wheel off the ground�known in big dog circles as a "stoppie". The important message for cornering is that rolling ON the throttle transfers weight rearward, and rolling OFF the throttle transfers weight forward, even if the brakes are not being applied.

Traction Control

I don't know about you, but when I'm leaned over in a corner, I'm very concerned about traction. I'd prefer that neither end loses traction and slides out. Now, remember that weight pressing down on a tire relates directly to available traction. Since both tires have about the same traction, it might seem that a 50/50 weight distribution rear/front would be the ideal. But we actually need more weight on the rear to supply traction for both cornering and engine thrust, so a 60/40-distribution rear/front is a better target.

Most everyone realizes that braking on the front while leaned over is an invitation to accept soil samples, but we must also remember that a trailing throttle is applying engine braking on the rear wheel. We realize the bike is slowing as we roll off the throttle, but we may not appreciate that a trailing throttle applies engine braking through the rear wheel only. Lots of riders have been surprised by the rear end stepping out in a corner rather than the front.

Adding a little "trail braking" on the rear can punch through the traction envelope quicker than you can say "hey, what's happnin' here?" It's not that you can't use trail braking, but that if you've got enough traction for braking, you've got enough traction for adding some power. Rolling on a bit of throttle while leaned over not only helps keep the bike up on the suspension, but also provides more traction back at the rear wheel to keep it from stepping out.

Smoother, More Predictable Lines

If you think through all the theory, you can understand why throttle control in corners contributes to smoother, more predictable cornering lines. Rolling on a bit of throttle as the bike is leaned over helps stabilize the suspension, lifts the bike up to increase leanover clearance, distributes weight rear/front to maximize traction, and smoothes out the mid-turn wobbles. Hey, that's what we said back at the beginning, right? One item we didn't tick off is that the "throttle on" technique also works well with delayed-apex lines, where you mentally slide your apex a little farther around the corner. Let's put it all together now, and see how you can improve your cornering.

Start the turn from the outside�the left side of your lane approaching a right-hander, or the right side of your lane approaching a left-hander. Roll off the gas and brake as necessary to slow the bike to entry speed, and then get off the brakes. Lift your head and eyes up, looking as far through the corner as you can. Swivel your nose around to point exactly at your intended line.

At the turn-in point, push the bike over with one smooth push on the "low" grip, and simultaneously ease on the throttle. Your goal is to be able to keep easing on a little more throttle all the way through the turn. As you lean the bike, tilt your head to keep your eyes level with the horizon. Point the bike�and your nose�at a "delayed apex". At the apex, roll on more throttle to lift the bike up, and plan ahead for the next turn.

Let's also suggest that one steering input per curve is the ideal. Yes, you can make small adjustments to your line while turning, but every steering input eats up traction, which can become a precious commodity if you suddenly encounter a hazard such as loose gravel mid way around the corner. Ideally, push the bike over towards your intended line with one precise push, and then stabilize it with the throttle.

So, What's Your Technique?

Next time you're out for a ride, try to figure out how you are using the throttle during curves. If you consistently find yourself running wide halfway around a tight turn, that's usually a result of leaning towards the inside too soon. Concentrate on getting the bike way out towards the edge of your lane before leaning it over, and then get it pointed towards a nice curving line that kisses a delayed apex as you lean it over and ease on the gas.

And, if you keep getting the urge to chop the throttle halfway around, that usually means you didn't achieve a slow enough entry speed before leaning the bike. Concentrate on slowing down more before you lean. Your target entry speed should be whatever will allow you to smoothly roll on the gas all the way around.

Throttle-Brake Transitions

There are times when you'll need to transition from brakes to throttle, and they may occur at mid turn, so we'll suggest a practice exercise to help you gain some smoothness. Next time you find yourself on a straight section of a vacant road, practice transitioning from throttle to brake to throttle as smoothly as possible.

From a steady 40 mph or so in third gear, ease the throttle closed as you ease on the front brake, then ease off the front brake as you roll back on the throttle. We're not talking snapping off the gas and grabbing the brake lever here�we're talking smooth transitions where you're still easing the throttle closed as you squeeze on the brake, and easing off the brake as you roll back on the gas. Yes, this is difficult, but it will prepare you for smoother corner entries as well as braking while leaned over.

Terms

  • Apex: the location on a curve where a motorcyclist will come closest to the edge of the road.
  • Delayed Apex: an apex imagined to be farther around the curve than where the rider believes the sharpest part of the curve actually is.
  • Inside: the right edge of the lane in a right-hand curve; the centerline in a left-hand curve.
  • Leading throttle: rolling on just enough throttle to keep the engine pulling the bike forward.
  • Outside: the centerline in a right-hand curve; the right edge of the lane in a left-hand curve.
  • Stoppie: braking hard enough on the front wheel to lift the rear wheel entirely off the ground.
  • Target Entry Speed: the desired speed prior to leaning the bike into a curve.
  • Trail Braking: applying either or both brakes while decelerating and leaning into a turn.
  • Trailing throttle: decelerating with the throttle closed to apply engine compression braking to the rear wheel only.

SR!


David Hough is a long-time motorcyclist and journalist. His work has appeared in numerous motorcycle publications, but he is best known for the monthly skills series " Proficient Motorcycling " in Motorcycle Consumer News, which has been honored by special awards from the Motorcycle Safety Foundation. Selected columns were edited into two books Proficient Motorcycling and More Proficient Motorcycling , both published by Bowtie Press. He is also the author of Driving A Sidecar Outfit and a pocket riding skills handbook, Street Strategies.


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