Your principal problem is the aerodynamic profile, center of balance and grip.
We run inclining our torsos and waving our arms, forearms and hands to and fro. That creates turbulence. To say nothing of our frontal profile, created by Face + Torso.
Center of balance.
The head of a cheetah is at our hip. To maneuver around an obstacle we would need a gentle course correction, instead of turning on a dime.
When a pneumatic hammer strikers the asphalt, it tears it apart. There is only so much force you can apply before tearing the surface you are using.
The alternatives are: increase the surface or increase the time of contact.
In order to "run", the maximum time the soles of the robot are touching the ground is going to be finite given a certain speed and leg length.
Boston Dynamics got a mechanical cheetah to clock below 50 km/h.
Boston Dynamics Robotic Cheetah Clocked At 28.3 MPH
That gives us a nice baseline for real and proven data.
Even if we indeed could reach the same speed as a F1 300 Km/h, there are inherent limits to the ROBO-FLASH body if it needs to be humanoid.
Unlike the F1 car, you don't have spoilers to generate down force in order to squeeze out more traction. Human body shape lacks spoilers. Unless you twist the Robo Flash ears :-P
Seriously, this is IMHO the main limit. The F1 cars generate extra downforce in function of speed. In excess of 2000 kgs. Some even generate so much force that it makes the asphalt ripple. Without it, the tires would rotate in place, overcoming the ground friction limit.
2 legs. The feet size is finite so you could theoretically make it run on all fours, giving you extra 2 points of contact with the aid of hands.
No tail provides fewer means to control the sharp turns. Soo good luck if there is a single obstacle in front. We are already hammering the floor with RoboFlash powerfull servo legs. A jump means extra force -> pneumatic hammer effect.
All of this without even a single mention of energy considerations, heat, etc.
I have no clue on how to determine the maximum speed for RoboFlash.
I would start with the maximum mechanical force a shoe sized piece of asphalt can take and go from there.