there is a tradeoff for more rubber and less wheel as well ...tire and body roll while turning /acceleration/braking....at the end of the day this 700xx is not a mx bike ...never will be ... so that mx line of thinking does not apply to an endurance machine. its the same principle with the front tires ... which is why the solid bead down the center of the wheel makes it much more responsive to turn...and to go straight as the surface a baja or gncc rider is on is always changing ... not like a groomed mx track. put some flat tread tires on your machine and ride ... the control is terrible ..almost uncontrollable at mega-highspeed ... which is the point but only exaggerated... so a trade off like previously stated ... you wanna go 50 as fast as you can get there because thats all the speed you need ... or you can cruise in style tuned for 80-90-even 100mph.
because mx bikes have a solid rear ...the additional rubber makes up for some of the suspension flaws...and added traction... there may be more meat on the ground ..by a zillimeter or 2 ... but you dont want more meat on the ground when you are pounding a baja circuit going 80-90mph for hundreds of miles... thats what the suspension is for.
i think everyone is correct in what they are saying here ... but just talking about different things.
No these quads are not made to be a mx quad, but you have to udnerstand, what is mx racing? It is a manmade track made to mimic obstacles we encounter out in trail riding, minus the rocks and roots. Jumps, berms, hills, downhills ruts are all a part of trailriding.
now again were not talking about gearing at all. this is not about why they use 18" tires, its about why they use as little rim diameter as possible. this is not about top speed or acceleration.
The reason they want more tire/less rim is because it helps handling. More rim/less tire will result in sliding instead of grabbing, and also gives more chance to a bead popping. With an IRS quad, more tire/less rim will help even more on these types.
MX racers are not trying to fix a "flaw" in their suspension systems. Most of these racers have better suspensions then we will ever dream of having. A SRA quad is not inferior to a IRS quad at all, theyre just made differently for different types of riding. If IRS was superior everyone would be using them in racing.
so my point is, a 10" rim will work great on these quads, and the smaller diameter rim will only help in traction and handling not hurt it. Dont trust everything that Honda does as gospel, theyve always done stuff that leaves people scratching their heads and cursing them. Its not that big of a difference anyway, not like we're talking about using a 8" rim with a 22" tire.
IMO save your money and just buy 10" rims, youll be more then happy.