This weekend’s British Grand Prix at Silverstone is the next venue for MotoGP. The 3.666-mile circuit is the longest on the calendar (the race is 20 laps, 73.32 miles) and located in England’s South Midlands, north of London. England is an island between the stormy North Sea and the likewise stormy North Atlantic, so rain, cold and wind are always possible. In 2010, Jorge Lorenzo won going away in the dry, the flowing circuit and fast corners favoring his Yamaha. Last year, the factory Yamaha men lost front grip in cold rain, crashing out as Casey Stoner took an out-of-reach win on his Repsol Honda.
Silverstone is a tough circuit for tire choice, because when the weather is cold, tires cool so much between corners that they stop gripping. Stoner said that he couldn’t ease up despite his big lead because the resulting loss of tire grip wouldn’t let him. Similar effects of tires cooling between corners have been blamed for crashes at other circuits, including Mazda Raceway Laguna Seca. This effect, plus the danger of the first three laps after the start (when riders must choose between losing position or pushing too hard on cold rubber), caused Bridgestone to produce faster-warming tires for this season.
Silverstone has a long history, beginning as a triangle of three wartime RAF runways and later continuing as the home of the British Formula One GP. The Isle of Man TT ceased to host motorcycle GPs after 1976, so that event came to Silverstone. Many remember the race-long duel between Kenny Roberts and Barry Sheene in 1979, won by Roberts on the drag race from the last corner to the flag by two feet.
Bikes went to Donington from 1987 until the return to Silverstone in 2010. Age has, in effect, “wrinkled” this track, adding first-gear corners then punching in the north side to form the infield “Arena” section. The result is 18 corners, 12 of which, by Yamaha’s reckoning, are taken in either first (4), second (4) or third gear (4). The Hangar Straight allowed Andrea Dovizioso’s Honda to reach a maximum of 180.5 mph last year.
Tires and bikes need stability for sustained turning in the fast Maggott’s and Beckett’s corners, and braking after high-speed sections. There are bumps, probably the pre-corner ripples caused by heavy race cars braking.
Last year, Hondas held a clear advantage in drag-race acceleration from slow corners up through the gears on high-speed straights. Yamaha has now made up some of this deficit. Yamaha has also added new software whose purpose is to help riders conserve tire properties (necessitated this year by changes that have made tires behave more like long-lived qualifiers: quicker to temperature but also quicker to fade thereafter).
This is a right-hand circuit, so spec-tire-maker Bridgestone will supply asymmetric rears with durable medium rubber on the right and a choice of soft or extra-soft on the left to maintain grip in the “expected cool conditions.” Rain is another matter; rainy England created the trench coat and Burberry. Google the forecast.
Who’s hot? Here are the top-five finishers of the past two years:
|2010 (dry)||2011 (wet)|
|1) Lorenzo||1) Stoner|
|2) Dovizioso||2) Dovizioso|
|3) Spies||3) Edwards|
|4) Hayden||4) Hayden|
|5) Stoner||5) Bautista|
Now for the tire controversy: This is the first weekend when Bridgestone supplies only the new-style front tire, called “the 33,” of which only two per team were distributed at previous 2012 events. This new front makes the Honda men angry because, to them, it is “a Yamaha tire.”
One tool used by Bridgestone to make its 2012 tires warm up faster is to make the carcass more flexible. As the tire flexes in those critical first three race laps, that flex generates heat to get the rubber hot enough to grip.
Traditionally, Bridgestone’s GP tires have been extremely stiff in the carcass to provide the necessary stability for braking and sustained turning, and to brace the footprint against squirm and buckling, which can cause the tire to lose grip.
The Honda riders, Stoner and especially Dani Pedrosa, say that the 33 doesn’t provide the stability necessary for straight-up braking and that it has produced chatter not present with previous tires (this, in addition to the rear chatter Honda has fought all year, seems just too much!). Stoner says that to get the stability they need, Honda increases front tire pressure, which, in turn, reduces footprint. Then, when riders need turning grip, “the front wants to tuck.”
Yamaha is not troubled by chatter, and Lorenzo has said the 33 is a safer tire on braking (a softer construction can potentially lay down a larger, grippier footprint).
This is the great conundrum of a spec tire series: that no tire can equally meet the needs of all teams, and that bikes are much more difficult to adapt to tires than tires to motorcycles. Add in the fact that the teams needing development to adapt to the new tire (Honda) have up to now received only two per race. How can you adapt to a tire that you can’t get?
That’s the frying pan, but the fire is tire competition. What if one maker so dominates, as Michelin once did, that other makers’ tires are seen as useful only for beach-party bonfires? Choose your poison.
How does a tire work for one bike and not for another? If Honda knew, they’d fix it! Maybe the chassis flex necessary to make the Yamaha grip and handle happens to be compatible with the 33, but the different flex in the Honda makes it chatter? And how can the Yamaha be stable in braking and the Honda not? Perhaps the 33 wanders side-to-side just enough to upset the Honda’s stability during braking but not that of the Yamaha. We can hope answers will become evident soon.
In 2006, it was Yamaha, invisible behind the chatter 8-ball, and Honda who had the workable solution. Such things are subject to change without notice, for new parts or tuning tweaks can change everything We hope for a straight contest among the top men—Lorenzo, Stoner, Pedrosa and Dovizioso—but the weather and complexity of the motorcycle’s eternal problems will decide.