Just a quick "correction" on the physics involved with wheels hitting brakes. This is almost always cited as being the result of a wheel not being "stiff enough." That's actually not at all the case. The flat 900 disc is the wheel that most notably "hits brakes." The reason for this is because the wheel is EXTREMELY stiff laterally. Too stiff, in some people's opinions.
Think about why the wheels are hitting the brakes. There is no force being applied laterally at the top of the wheel. When people push on their wheels at the bridge from the side and say "look, it hits the brakes!" that is totally unrealistic. Try to imagine how you could ever generate that force while actually riding. What is actually happening is that the bottom of the wheel is getting move left/right as people stand and sprint. When a wheel has extreme lateral stiffness, the top will move left to right an equivalent amount. If a wheel has some reasonable amount of flex built in laterally, it can "suck up" this lateral travel of the wheel underneath the bike.
So when wheels hit the brakes, it's because they have TOO much stiffness, not because they have inadequate stiffness. The end result is the same, of course, your wheels are hitting your brakes, and that's a problem. But the actual reason why it happens is basically opposite of what people think. 808s are MUCH stiffer laterally than 404s. It's a lot easier for me to ping my brakes with 808s than with my 404s. And it's easier to ping it with 404s than with 303s. It's easiest to ping brakes with a 900 disc. But it's because the wheels are too stiff.
One thing to think about, though, what this means is that you are pinging your brakes because you are moving your bike a fair amount left to right. More flex in your wheels will help accommodate this. But the other thing you can do is NOT move your bike so much left to right. Keep in mind that all of the protour sprinters are running the exact same wheels you are. They don't ping their brakes (and Cav regularly runs an 808 rear). And the reason is that they move their body left to right a LOT, but the bike holds a very straight line. Moving your bike left to right is not going to make you go any faster. So if your wheels are/were hitting your brakes, it's not a problem with your wheels, it's a problem with how you sprint, which is a good thing, because it means there is "free" speed on the table.
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