I have thought about it and here is my theory:

He's going around a curve, so centrifugal force comes into play.. I'm sure they're not able to go full throttle into curves because centrifugal force would throw them violently into the outer wall.. BUT if he skims the outer wall, he can go wide open full throttle because the wall itself is keeping him within the boundaries of the curve.. he doesn't hafta worry about being thrown into the wall violently, because the wall itself is stopping him.. so he was able to go wide open full throttle, passing all the other chumps who slowed down for the curve.....?

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Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..