How to determine maximum speed for a given bicycle gear ratio?

This question came up watching a final sprint at the Vuelta San Juan this year. One of the riders was sitting down in the sprint because he had "spun out" his gears, meaning there was no longer any resistance in the drivetrain to his pedaling motion. The commentator mentioned that in order to spin out a gear ratio of 53:11, you would have to be going fast. How could you determine this speed?

Here was my first approach. At first I used one of the gear equations:

I estimated that at 120 rpm your legs would no longer feel any resistance to pedaling (this may be a little high realistically). I did some calculations and conversions and got a linear speed of the bike of 46 mph. This seems pretty realistic given what I know about bike racing.

However, I was wondering if there is another method to this. Could one develop an equation like this:

Then set the torque_pedal variable to zero (or near zero) and find the velocity?

I attempted several equations but couldn’t come up with something that worked. Either the values seemed unrealistic or I just ended up with x = x, or everything cancelled itself out. Here are the starting points I used:

F = ma

I can’t seem to really get the intuition of the problem this way. I guess you would be looking for the rotational speed of the rear wheel such that the 53:11 gear ratio could no longer accelerate the rear wheel?

Anyone have any ideas on this?