Guest Blog: Mat Oxley - An anti-chatter jounce box? is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.

An anti-chatter jounce box?

Last year Ducati’s Gigi Dall’Igna maddened many with his wings, now he may have solved an age-old problem with Formula 1-inspired jounce-dampers

This year’s brand-new MotoGP bikes are currently on their way from Malaysia to Australia for the second preseason tests, which take place next week at Phillip Island.

If you are a motor sport fan of a James Bond bent it’s tempting to imagine an industrial-espionage agent dodging through airport security to stow away aboard Dorna’s cargo plane, where he prises open Ducati’s flight boxes to disassemble that little black box at the back of Jorge Lorenzo’s GP17.

Make no mistake, this stuff does happen. Some years ago, when Michelin dominated MotoGP, it also supplied its super-secret MotoGP tyres to Honda’s British superbike team. At the Mondello BSB round someone broke into the Honda truck under cover of darkness and removed one rear slick. No one knows who took the tyre, but how could anyone have wanted it for anything but dissecting the rubber and casing to discover its secrets?

After last week’s Sepang tests there is still plenty of speculation about what’s inside Ducati’s little black box. I guessed it might contain a chatter-damper or (more fantastically) a gyroscope that optimises the motorcycle’s dynamics during acceleration and braking.

A gyro might be illegal because MotoGP rules state that ‘electronically controlled suspension and ride-height systems are not allowed’, so a chatter-damper makes more sense, because tyre chatter is a major performance inhibitor in bike racing.

Chatter is caused by high-frequency resonances – emanating from the chassis, suspension and tyres – which can overwhelm the suspension hydraulics. The chatter vibration is thus transferred to the tyres, with a disastrous effect on grip. Particularly severe attacks defeat the suspension so completely that you can sometimes see daylight between tyre and racetrack. And daylight doesn’t grip very well.

Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.


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Interesting. I have to differ on one point however, from my experience, chatter is produced by too much traction. Ride harder (tough) or increase tire pressures/switch to a harder compound to solve. Simplistic, but it seemed to work on my stone age stuff. 

I find it very interesting that a decade ago all the manufacturers, lead by Honda, were clamoring to centralise the mass of the motorcycle.  This lead to lots of complaints that Honda (for instance) were preferencing the smaller riders (like Pedrosa) and penalising the larger riders (like Hayden - who had just won the WC).  I understand that mass centralisation gives easier handling, but it did always seem strange to me that they centralised the mass so much - when the ratio of sprung to unsprung mass/inertia is such an important part of handling.  It's quite interesting that they're now (probably) experimenting with putting (simulated) mass back into the extremities to solve the ever increasing chatter problem.

In physics, jounce or snap is the rate of change of jerk which is itself the rate of change of acceleration.  Acceleration is the rate of change of speed and speed is the rate of change of position. 

Suspension position is controlled by springs, velocity/acceleration is controlled by dampers, jerk by intertia dampers and jounce by jounce dampers. 

It's just increasingly sophisticated control of wheel movement because the longer we can keep the wheels in contact with the ground, the faster we can go


Is there a 5th derivative?
They become dramatically less relevant and more subtle each time, right?
I understand dampening the 3rd derivative, straightforward enough for suspension up and down, the fluids must do a nice dynamic job w the finer 4th derivative eh?

Trickier at lean obviously, working w metal materials. Obviously we have some absorption going on, and non-geeks like most of us know rubber mounts for engine vibration and bar end weights for the same. But the bike at lean getting something TUNABLE for jounce?
Our salad box could be...
(Keeping the front end down, or also bringing chatter down?)
Very cool, thanks, and more please!

Not because the joke wasn't awesome, because it was, but because somebody must have voted it down for it to be at only four out of five stars.

Why?  Who is that grumpy?  This is an objectively funny joke.  It doesn't harm anybody.  It's impossible for cgates66 to be "wrong," in that he was merely telling a joke.  If you like the joke, maybe give it five stars.  If you don't, why vote at all?  Why does one feel the need to disapprove of something so harmless?

Okay, bake to my cave...

It appears that the inerter on f1 cars mount between the frame and the suspension and store some the up and down motion as rotational energy. Wouldn't there have to be some connection to the swing arm for this devise to be a true Inerter?


It is far from the pivot point of the swingarm, far from central mass. My non geek starts thinking it is an inert piece of weight that inerts chatter. But I am not satisfied w that explanation at all. I am having trouble thinking it is an active device to keep the front end down, and assume they have a fairing like the Yamaha's coming for the wing replacement.

The salad is to get it to turn better mid corner, or correct for something (chatter) that comes up when they do something else to address turning.

Or a turtle?
Quick anecdote - I took a break from psychotherapy to do a stint caring for the dying, while doing the Tibetan Buddhist equivalent of seminary. An "origin story" we learned is of a "primordial turtle" that was under the ocean. It is an old folk story from India, not necessarily Hindu. It has represented something original that was without cause. You may see them from time to time on incense burners etc. The cool part is that is frees the divine from needing to be creator, and more like a natural force that is elemental.

I wish them luck!

Maybe not salad. How about sip of water. Could it be tank for water injection system. Gigi have been saying something about discovering new things engine side.