Cycle News - Archive Issues - 1990's

crankcases like on the 926, but is also supported by the rear chassis section for extra rig id it y - especially important when the e ngine gets hot and the swingarm bearings can get sloppy. Beginning last winter, chassis development concentrated on finding good settings for the Ohlins rear shock and 46mm upside-down fork - fitted instead of the Showas on the street version - and resolving a high-speed stability problem, Part two of Alan Cathcart's Riding the World Superbikes features a look at the two Ducatls currently used In the series - the new 926 (4) ridden by Fabrizio Plrovano and the old 955 (11). The 926 has the sleeker profile and better aerodynamics, but the 955 has still fared well In the hands of Andy Meklau and U.S. Superblke Champion Troy Corser. ly the position of the valve guides, which is critical - there's just one guy in the Ducati factory who knows how to do it perfectly, and it's worth eating up the road between Vienna and Bologna to see him. He's an artist!" . PIROVANO'S DUCATl955BRINGING UP BABY Co nsidering that an intensive test program began as long ago as last October, a full seven months before the first round of the '94 World Superbike series at Donington in May, it seems curious that the·955cc race version of the 916 Ducati launched at the Milan Show last autumn has suffered since its debut from handling prob le ms that you 'd have expected would have been dialed in during preseason testing. Still, Honda have taken even longer not to get their equally new RC45 handling right on Showa suspension, and at least Ducati now appear to have the all-new chassis designed by Massimo Tamburinip roperly sorted. They fou nd the answe r after a crucial series of tests at Muge llo, just before the Austrian round, unlocked a setup that enabled Carl Fogarty - who for some curious reason wasn't brought in to ride th e new bike un til just before the seaso n started because Falappa was preferred to hand le all the off-season development to lap the Italian track in an incredible 1:55 time that wou ld have put him in se venth pl ace for the 500cc Italian GP run the week before - level with Kevin Schwantz a nd ahead o f two NSR500 Hondas, " Bu t the pecking order within the Ducati works team that now sees tes trid er Mauro Lucchiari first to try out a new part or setup which, if it works, is then given to Fogarty, then to Pirovano and Whitham, meant that when I rode Piro's 955 at Zeltweg it d idn't ha ve the benefit of this improvement. That meant it was in the same basic spec as at the second round at Hockenhelm, where Fabrizio finished second after leading much of the way, his equal bes t result of the season, and third at Donington. But against this, Pirovano has had no less than eight retirements this season through engine failures, posing a question against the Tardozzi team's preparation or Fabrizio's rid ing style, honed on a decade of riding four-cylinder Yamahas and Bimotas, or both. The 96 x 66 mm long-stroke version of the eight-valve demo V-twin has had some midseason va lve problems, most notably at Zeltw eg w hen everyone but Fogarty lost at least one motor, and then again in Indonesia when the Brit was the one to suffe r. The p roblem was caused by fining titanium valves, in an effort to give the rockers an easier time an d allow use of wild er cams and more revs, bu t after revertin g to nimonic valv es and reducing preferred revs to 11,500 rpm, the problem wa s apparently cured for Assen, But even there Pirovano blew an engine in the first leg. Otherwise the . new lo ng-stroke desmo has been pretty reliable from the start, confirming Ducati's decision to use it in 955cc form this season was right. After the Ferracci team 's 1000;. finishing record at Da ytona - four started, and four finished the gruelling race on the engine-killing bankings - th e fact o ry could be confident the new engine was dependable, and apart from the valve problem, that's how it's turned out. , In 955cc form, the V-twin desmo delivers 151 bhp at the gearbox at 11,500 rpm, running with the oval under-seat silencers and slightly more restrictive exhaust system of the 916 package. In the form we raced the bikes at Daytona, there was mo re th a n 155 bhp on ta p, because of the freer-flowing exhaust system permitted by the olde r 888 chassis. Yes, it would fit on the 916, and superbike rules would allow it, even if a lowbo y silen cer on eac h side would look quite d ifferent from a 916 roadster . But tha t would be a marketing d isaster, so while Ducati keep wo rking to fin d the extra bhp locked up in their exhaust system, that's the wa y it's gonna stay. Apart from the long-stroke crank and - even with nimonic valves - wilder cams giving lots of lift, a fast op en ing ramp and a long dwell, in line with current Formula 1 practice for fu el- in ject ed engines, the 955 engine internals are similar to the 926, with titanium rods, Omega pistons, a slightly lower 11.6:1 compression, six-speed gearbox with no choice of alternative ratios (why bother, with so much torque) a nd a slipper clutch. But the chassis is completely different, with the engine rotated forward 3 degrees, compared to the 888/926 frame, to obtain a shorter 1410mm wheelbase (vs. 143Omm) and allow the head angle be steepened half a degree to 24 degrees. The d istinctive single-sid ed cast swingarm p ivots not only in the initially by fitting flatter 25mm fork offsets to increase trail. Then in the first roun d at Donin gton, all the riders had trouble keeping the front wheel anywhere near the ground ou t of the thr ee slow turns, as well as with getting traction for a smooth drive. Part of that may have been a tire problem, but a cut-tnshut job on the rear swingarm added 25mm to the wheelbase. That helped, b ut it d idn't cure the speed wobble that sometimes occurred Under hard acceleration. Ohlins' suggestion was to reduce the speed of the shock in favor of a more progressive action , by altering the leverage ratio from 2.03 to 2.30, pe rmitting use of a stronger spring. It worked - but then Ohlins technician Anders Andersson is a very clever man. Still, the wheelying and traction problems haven't been completely banished, and Ducati are still trying to figure out whether they need a pro-squat or antisquat rear sus pension setup. At Zeltweg, for examp le, in some turns, riders would get hard on the gas a nd th e back end wou ld squat, ma king the wheel chatter and the bike run wide on the exit - hence the very stiff spring fitted to Pirovano's bike in spi te of his light body weigh t, which of course compromises sus pe nsion response over bum ps. Steering geom etry is changed for each circuit - for twisty Albace te, w ith its peculiar lack of grip (ask Scott Russell), Ducati moved to 30mm offsets to reduce the trail for quicker steering, but a lso re fitted the sh orter s wi ng a r m, to improve traction. Then for Zeltweg they went to a 32mm offset, but the long swingarrn for better fron t grip, coupled with another rear suspension link - the one Fogarty went Schwantz-hunting wi th timewise at Mugello. Every rider prefers a different rid e-height setup, too. Fogarty likes a lower rear end for a more balanced feel , whereas at the other extreme Pirovano likes it jacked right up, w ith lots of we ight on the front wheel. Fogarty even tried the bike at Albacete with 6.6 pounds of ball ast strapped to the rear seat subframe, to try to imp rove rea r end grip. It didn't work, but only added to the 326 pound half-dry weight of the 955, compared to the 926' s 334 pounds. Ducati's achievement in making the 916 in to a w inner from it s very first World Superbike outing, and a hot con- -.:t< 0\ 0\ ~ I-< (1) ,..Q .8 u o 27

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