I was sitting here thinking about the design that goes into MotoGP bikes, and a question popped into my head. Why are big bikes slow on tight courses? Is it because of the added weight? Different steering geometry? Longer wheelbase? I'll use the R1 and R6 as examples, as they are pretty similar.
Added weight shouldn't matter, unless I am missing something. The R6 weighs 160kg compared to the R1s 170, but produces only 120hp compared to 180 (2004 models). That's almost a 3:2 power:weight advantage. All else being equal, in a turn the bike's weight is what keeps the tires from sliding out (normal force, friction, and all that jazz), so the act of tipping the bike over should also be pretty equal (especially with the weights being so similar). There's nothing stopping the wheels from having the same dimensions and moments of inertia, so cornering ability, based on weight alone, should be more or less equal.
I don't see why a different steering geometry is necessary, if both bikes are to compete on the same track. Perhaps the R1 has a larger (rake? trail? don't have a diagram to help me figure out which affects what) to help steering at high speeds, but that could be modified if one was so inclined, to be better suited to a tight track. Both bikes can be made to brake equally hard, so on the same track, there has to be an ideal setup (wheel further out to prevent stoppies vs short wheelbase for sharp turns) that would be more or less the same for both. Also, a steering damper helps funny stuff from happening at high speeds, so sticking a good enough model on the R1 should allow the forks to be at the same angle at an R6, and still be stable at near top speed.
The R1 and R6 wheelbases differ by 15mm (1380 vs 1395mm). That is a very small amount. Can't the swingarm be shortened by that amount, or the swingarm pivot be moved forward by that amount, if the 15mm really matter? Is this the reason people say the R6 is better at Mission?
Since wheelbase helps cornering so much, why don't we see MotoGP bikes with flat 0-degree engine designs (lower CG -> can shorten wheelbase w/o having endos happen). Are the heads really that close to the front wheel? Can't some team of engineers come up with a design that allows the engine to hang out the back of the frame, with the swingarm and shock designed around it? I'm always happy to learn new things, and I know lots know more than me. What are the reasons for these things?