Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/1542351
Ba 'Fhe man of the testing momenr, Troy I Bryi==, on.. .r-.e set the world on fire with his superb one-lap and mce-tire pace on his Xerox Ducati, blazing around the 2.4&mile Valencia circuit in Spain with a new unomcial best superbike lap. Bayliss became the lirst world Superbike rider ro crack into the lr33s, and he simply smash€d his waytoan eventual l:33.758 in the morn- ing session of the last day, l"larch 29 . Were it not for an oil spill from hit maahine on day one (the team clairn€d that debris got stuck on the rear tire, and that cut an oilcooler hose) and a cmsh when the wind got under his bike later on. it \,tould ha,/e been a perfect test for the prodigal Bayliss. "When I woke up this morning and saw that the conditions were good, I knew I could do some quick times," Bayliss said. "l immediately did a 34.7 on my first exit on race tirec- We tried a few more thin8s this morning. and then I put on a Q-tire to set the time. My first long run in the afternoon was not as good as we e"\pected, but we made a few changes to the front and rear and did a great full-rdce simulation. My last lap was one-tentfi of a second slower than my best lap, so we did eveD,'thing we set out to do, I've been wanting to do a I+ in the 33s here for some time, and I'm feeling great about it. Ruben [Xaus] also looked good today. lt feels really stranse to have my former teamrnate ahd my current team- mate behind me!" Ducati's wish to be allowed to run l200cc bikes in world Superbike took on the air of "why?" once again, as SterilEarda gerik Ducati's Rub€n Xaus was second fastest, and, like most of his pee6, he set his best lap in the cooler mominS session on Wednesday. Xaus' impressive return to action in world Superbike in 8eneral is all the more noteworthy due to the faEt that the tough Spaniard is still relyint on crutch- es to get around when h€'s off the bike, after an oIf-season training accident. Still, he's hard as naib and faster on his year-old- spec Ducati than any ofthe impressive line- up of fours. ln third place overall, after the conclusion of three glorioust sunny if interminabt breezy dap, was Bay'iss' Xerox Ducati teammate Lorenzo Lanzi. The little ltalian made it a top- three sweep for the big desmo twins, ortpac- ing Troy Corser ard his Alstare Suzuki Corona Ext a, the reignin8 World Champion more than a second Hfnd his Aus.Bie riral Baylirs. "Today we aarried on tryint a whole load of different stuff, and maybe we got a little confused," Corser said. "Many times ! went out to test somethin8 and was out for four or five laps to find olt as much as possible. We have been here heaps of times, so we have a pretty good idea of a base setup, so that was romething we didn't feelwe had to chase this rime. All in all, it was a pretry productive three daF, and we ended with lots of info and data Today the clurch Mras pretty consis- tent, and h se€med okay even after I had done a practice start, Now we have got a short break before our next test in Misano. There we will have to concentrate more on llnding a Sood setup for the race." The fact that Petronas Racing's Stwe l'4anin impressed the onlookers was no sur- prise for the most self-eflacinS rider in the paddock, but when he iSnored the handi@p of havinS l00cc leis en8ine displacem6nt at his dispoial than mo6t ofhis competitors, and put the unique Petronas FP- I fifth - out of 28 riders - then somethint tpecial had iust h+- pened. His brilliant displa,, in the mornint continued in tfie afternoon of day thre€, and even a late fall, in which he banged his head and ended his day, could barely detract lrom his perforrnance. "l have ro ride about 125 percent to get a hp time like that, but my crash was iust my fault," Martin said. It was Martin's second off-track evert of the te6t. Martin's teammate Craig lones was last overall, as he learns the Sup€rbike and World Championship ropei. Unlike almost every other rider, Yamaia's Noriyuki Haga beat his previous personal best in the final aftemoon s€ssion, desphe the track grip degrading as the day went on. lt's a funny old rack surface at Valencia, and it caused an early unwrapping of qualifiers; one can catch it at its best in the a.m. Haga, test- ing new fork settints and a re\ramped entine mapping curve, was sixth overall. and he put his unusual afternoon betterment down to continuous improvements from day one, despite a slide-off early in the tests. Another GP refugee, Fonsi Nieto, ended up seventh in the overall classification on his PSG-I Kawasaki, hiShly impressed with the new work done on his big ZX 10. His team- mates Chris Walker and R€tis Laconi were l2th and l7th, respectively, with Walker try' ing out new brakes as well as a whole host oI chassis and engine tlveaks. Only Laconigot to play with the new rear swingarm and suspen- sion linkages, and he enioyed the new ride, as he went back !o his old smiling self- For a guy not usually satisfied with any- thing less than top placin8s, eiShth for Andrew Pitt was a good day of work. He spent most of his time workinS to ensure that he will have a fast and consistent setup lor the Valencia race itself, and he liked the new engine-mappinS curve as well. The best Honda rider was a pleasant sur- pdse to some, a5 young ltalian Miche! Fabrizio (DFX Honda) got the better of Klaffi Honda rider AJex Barros' good firct- day start, to take a top-nine classillcation. Barros was to finish llth, and the top l0 was rounded out by Corser's teammate Yukio lGgayama. For Barros, a new enSin€ was no rcal solution to his new problems, as he finds the Superbikes are very dillerent lrom GP bikqi, especially in terms o{ priority of sup ply for new spare parts. Berros' woes were nothing compared to those of another Honda ridet winston Ten Kate Honda pilot Karl Muggeridge, who suffered fractures in two vertebrae in a crash during a alow- down lap in the morning session. keliminary checks showed tha( he was in no danger of further injury but he is expect- ed to spend two months immobile while the bone heals. To the astonishment of most who'd heard the initial medical rePorts of Muggeridge's having to be flat on his back for two months before even stunding up, he walked back into the paddock in the after- noon, complete with back brace to immobi- lize his iniured spine- He was only lSth in the classification, as his early fall prevented MotoGP Tech: What ls Chatter? rhrottle because they would crash - so instead, rhe bike chatters and the tires just slide away. An easy way to feel chatter in lhe (omfort of your own home is to run a damp finger around the rim of a wine glass; your finger tip is the track surface and the glass is the bike. As soon as you hear the hum from the glass, you have chataer: and when that hummint vibration happens on a bike, it destroys a tire's grip on the road. But if the Yamaha didn't t ip the road so well in the first place, it wouldn\ have a prob- lem, and if its tires weren't so Srippy, atwould- n't have the problem- Apparentty, the Yamaha is so good that it h:s created its own troubles. Chatter is a collision of two resonant fre- quen.ies. Ever/thing has a resonant frequen- c),,; its iust a question of what it takes [o excite it - a guitar string has a frequenq/, one that you change by tithtening and loosening it. Keep it tight, and you get one note when you plu.k it: loosen it, and you te( anorher A sim- ple wine glass has a resonant frequency - flick it and it rings, but take that gla5s and add an opera sinter holding the riSht note and it will shatter Engineers know of the Tacoma Narrows Sridge, asuspension bridge where a certain speed of wind passint across the road set off a catastrophic reaction that destroyed the bridge. lfyou consider a modern bike. many parts make up that bike - and they all have their own frequencies; and under specific circum- stances, aay rvvo could collide and set off a catastrophic vibration. The fork has its own frequency, as does the main chassis, the wheels and even the engine. Yamaha's prob- lem is to understand the frequencies they have built into these units and the pressures that make them resonate. On motorcycles, the problem usually appears somewhere around 20 Hz {that's a vibration of 20 times per second), so it is no coincidence that et 60 mph. the wheels are circulating at around 20 times per second. This vibration will typically come from the tires' contact patch with the track, but it ont becomes a real problem when tha( vibration Up untilthe final MotoGP rest ofthe ofr season at jerez, the new Yamaha M I looked supreme. Sure, ther€ were a few "tire-vibmtion" prob- lems in Qatar, but surety nothing could stop the team's progress toward a third World Charnpionship. But then they went to the tiglt and tlvisr/ .lerez, and out to get them came motorcyclint's own little gremlin - chatter Valentino Rossi spent all of practice for lerez tr/ing to eliminate the chatter problems that have plagued them since the last of the rests a!lerez a lew weeks before the opening round of the championship. lv'lichelin's 2006 tires have more Erip than last year's, and when used in conjunction with the Yamaha chassis at Jerez, somethinS sets off the colli- sion of harmonic vib.ations that racers and crews refer to as chatter But just down the pit lane, Carlos Checawas also sufierinS from chatter - and he had Dunlop tires on his Yamaha. So maybe lhe problem had more !o do with the Yamaha chassis than the tires. Chatter only comes with Srip: The more grip, the wo6e the problem. lt looked as though Yamaha had solved the problem on Friday, when Rossi was fastest in practice, bu! the track w:s damp and siSnificantly less gnp- py. As soon as the warm weather returned, everybody else was able to go quicker and Rossi's chatter returned, What ls Chatterl Chatter is a vibration that is capable of buzzint rhe bike right off the track, though the Yamaha's problem seems far worse than conventional chatter. When the grip between tire and E_ack E really 8ood, it can create a vibration between the tire and the track. it only takes a small chanSe in load or track surface to triS8er the problem - and it only appears at full lean, usual- ly on neutral throttle. As soon as the rider applies power, the balarrce of the bike chanSes and the chatter normally dis+peaIs. There are, however, comers where they cannot apply IO APRIL12,2006 . CYCLE NEWS liss Storms Test o o I F tr ), | ', P iI t ( U J> I a Troy Boyli* led oll aomcrj ql lhG reaenl World Superbike resr in Volentio, Spoin.