Ducati 999 At Willow, Part 4
Andrea on Handling
Note: the following is a dramatic reenactment of conversations between our trusty correspondent,
I race a GSX-R600 and, by all accounts, our 600 is one of the best handling 600s on the track. Tight and responsive it allows for all sorts of ontrack gyrations to allow for quick and decisive passing. However, our 600 feels like a smoke blinded child helplessly trying to feel its way through the apex of a turn compared to a Ducati.
“You write for Roadracing World?” Forni questioned in heavily accented English as I dropped onto a chair with a bottle of ‘Ducati Revs America 2001’ water and a Halloween cookie.
“Yes” I responded.
“Do you know Melissa?” he inquired tentatively.
“Yes. I live with Melissa.”
“Melissa was in Valencia for the 996 two years ago. She was very fast and also very interested in the technicals of the bike. Very unusual for a lady, no? Say ‘hello’ to her for me.” I quickly decided to capitalize my new found Melissa connections to see if I could get the inside scoop on the Ducati handling magic.
“Andrea, Melissa races bikes and often has trouble getting the bike to handle the way she likes.” (note clever use of absent third parties)
“I remember she adjusted the suspension on the 996 in Valencia and went much faster.” Andrea reminisced.
“We were wondering what the secret is to the Ducati mid-corner feel. Why does a Ducati feel better at the apex than any other motorcycle.” and then I waited with baited breath.
“It is many factors. Many things that affect the handling. There is no one thing that makes a bike good. It is very complicated but, if you like, I will explain it with paper.”
Bathed in the golden sunlight that can only be produced by a filter comprised of the suspended particulates in southern California smog we sat on the pit wall and talked handling while the crew packed a semi full of 999s.
“First you must have a very compact design. You must centralize the mass of the motorcycle between the wheels and side to side. The more compact the motorcycle is, the less inertia moment to change the direction of the motorcycle in any direction.” So much for aluminum twin spar frames.
“There are three types of instability for a motorcycle. Weave, wobble and capsize. You are probably familiar with weave and wobble but the capsize is also very important. Capsize is the tendency of the motorcycle to fall over.”
“Now a motorcycle with a high center of gravity will be more unstable with regards to capsize so, for a big touring bike, you would not want to have a high center of gravity because it would be very difficult to control at low speeds.”
“However, a motorcycle with a low center of gravity must be leaned over further to take a turn at the same speed as a bike with a higher center of gravity. So for track use, a higher center of gravity will allow you to lean less for a given speed. However, if you are leaned one direction and have to pick the bike up to go the other direction, the higher center of gravity will create a longer lever and it will require additional force to switch directions. So there is a balance.”
“When testing, we will take a chicane with a hard left and hard right and use the data logger to record the maximum speed through the two turns, as well as the time it takes to make the transition. We will then raise or lower the center of gravity of the bike and run the tests again. Through this process we can gather the data and arrive as the best center of gravity”
“You must have very consistent riders to be able to accurately gather that data” I observed.
“Troy Bayliss, Ben Bostrom and Reuben Xaus are pretty consistent. They will go as fast as possible.”
“We use a data logger on our racebike” I said “We used to record suspension data but we found that we could never use the resulting data to make any meaningful changes. We found it was faster and easier to tune the bike based on rider input rather than data recorded off of the potentiometers.”
“Suspension data is very difficult to learn to read. There is useful information in it but it is hard to find. We will typically test for one day at the track, then spend two weeks analyzing the data. It is very time consuming.” Andrea discouragingly informed me.
“We have found with our race bike that we can gain benefits from raising the whole bike slightly on the suspension but that we have to be careful to raise both the front and the rear or we will change the rake and trail in a detrimental manner. You must be careful to adjust the front and rear in a congruent manner to avoid changing the rake and trail.” I said thinking aloud and revealing my simpleton nature.
“Yes” Andrea agreed “you have to be careful to separate height of the motorcycle from ride height. Also, the chain adjusters on most motorcycles are parallel with the swingarm, not to the ground so that changes in gearing, and chain length, will affect the ride height and the chassis geometry. We made the chain adjusters on the 999 to be parallel to the ground to eliminate that problem.”
Fuck, I eloquently thought to myself, I had never considered that.
“Then the geometry of the bike must be appropriate for the purpose of the bike. A track bike will need different geometry than a road bike or a touring bike.”
My head was still trying to figure out how to apply these lessons to our battle scarred GSX-R when I remembered my last question.
“How come the shock on the 999 doesn’t have enough rebound damping in it?”
Andrea looked a little appalled. “Did you adjust it?”
“Yup I turned it all the way in and it still came back too fast”
Andrea thought for a minute “Did you test it by bouncing on it?”
“Yes. And, on the track the bike would get a rear oscillation off of the rise between turns seven and eight and it would not recover for a few seconds.”
Andrea thought about it for a few minutes. “The rebound requirements of Willow might be somewhat special and if we made the shock work there it might not work so well on the street.”
I thought about that for a minute and asked “But why didn’t you make the range of adjustment so that the shock could rebound very fast or very slow so that the rider could adjust it for all sorts of roads and tracks?
“The Showa is a good unit, but the rebound adjustment is limited by its design. There is a better design which allows for greater range of adjustment but it is more expensive. I think the solution to the problem would be to fit an Ohlins.”
“Our MotoGP bike has a higher top speed than the Aprilia. The laws of nature governing the handling of a motorcycle are the same in world Superbike or MotoGP. We will be competitive.”