TECH UPDATE: What is Damping?

We thought we knew. Damping is friction. It’s friction that consumes the energy of an undesired motion. Damping is a soft hand on a ringing bell. Damping is the conversion of unwanted chassis motion into heat inside of a hydraulic damper.

Then it gets more complicated. More than one journalist friend—on two wheels or four—has reported being given a vehicle to test on track, then found that it does some things much better, and a few things worse. Was this some breakthrough new concept? No. Each person was told, “You have just experienced a vehicle without dampers—springs only.”

Such a thing takes more than a moment to digest. Then, however, some things begin to make sense. Former GP and Superbike rider Mike Baldwin used to tell his riding-school students: “Zero your clickers, compression and rebound, both front and rear. Then try a couple of laps to familiarize yourself with how that feels. Then bring in rebound damping a little at a time.”

He wanted his students to understand the plusses and minuses of damping.

The reason why vehicles without dampers do some things better is that damping interferes with the wheels’ ability to follow small bumps. Think of accelerating off a turn over the usual pavement ripples generated by the power of heavy racing cars. If you have dialed-in a normal amount of rebound damping, as your rear tire reaches the top of a ripple and starts to drop down the far side, the presence of rebound resistance, by slowing the tire’s drop, causes it to press less hard on the pavement and so, to spin.

Yet if the bike’s suspension is set into motion by a single bump, that motion will continue many cycles afterward if there is no damping to stop it. How to resolve this conundrum?

Nicky Hayden was known for liking rather less rebound damping than other riders. In an important Laguna race, as he and Mat Mladin accelerated toward the flag across Turn 11's exit ripple, Hayden's more loosely set up Honda hooked up and accelerated, whereas Mladin's Suzuki, stiffly set up for quicker response, spun up and lost the drag race.

Suspension consultant Dale Rathwell cleared the air in about 1992:  “To damp the frequencies that interfere most with rider control, the technology we have must damp all frequencies.”

He was referring to hydraulic dampers as “the technology we have.”

A lot has changed since then, with damping technology and in understanding precisely what is upsetting riders and interfering with their control and confidence.

I have previously written of a rider inserting his/her motorcycle into a turn while it is oscillating in “rocking-horse mode,” where the energy of the oscillation causes the front and rear tires to be alternately compressed. When a tire is at the top of this motion, it is exerting less-than-normal pressure on the pavement, and is thus more likely to lose grip and slide. So we’d like to suppress this rocking-horse motion before it can have a bad result.

Changing the suspension won’t help because the dampers aren’t moving; the flexible element is the tires, which have no clickers. At this point our team’s electronics tech speaks up: “Let me have a crack at it. I have an idea.”

You guessed it: His idea is to move the engine’s throttles very slightly, out of step with the rocking-horse motion. This is exactly like what you did as a child on a swing when you wanted to reduce the height of your motion; you “anti-pumped” the swing at 180 degrees out of phase with it.

The electronics tech (or one of the mysterious “laptop crew” in the room between the garage at the front and the storeroom at the back of the pit box) starts coding with lots of “if/thens” and multiples of “move the value in register 01001001 to register 10011010,” and as soon as appropriate values for the throttle motion are worked out, the Inertial Measuring Unit(s) on the bike report that the “rocking-horse mode” has been suppressed. The rider is no longer reporting mysterious grip loss during corner insertion.

And this in turn is why, as I learned this morning from respected colleague Neil Spalding, suspension technicians in MotoGP have rather less to do recently. The idea of “anti-pumping” against specific undesired motorcycle motions by means other than hydraulic damping opens up whole ranges of new possibilities.

Neil also said that in the past, when riders such as Casey Stoner or Marc Marquez have reported they are using very little traction control, the nostalgia-worshippers have fastened onto this as meaning these riders are doing without electronics. Not so. It is just that their teams have now moved beyond the first relatively crude electronics applications (the stuff now being featured on high-end street bikes) to more sophisticated and more specific interventions.

Now, imagine a bike whose most prominent unwanted motions have been “anti-pumped” into insignificance by suitable software. The rider, protected in this way from such upsets, needs less damping from the actual suspension, which may now follow bumps better than it did when every problem had to be mashed out of existence by damper trickery.

Why wasn’t this done before? Before Inertial Measuring Units were on all these bikes (remember, before you object, that IMUs sell for $100 now), the only motion- reporting came from suspension travel sensors ($800 each), which were unable to “see” tire flexure bounce. Suddenly one of the problems of corner insertion was brought to light—by IMU reporting.