Which of the following actions is crucial when handling a flat tire on a motorcycle?

When handling a flat tire on a motorcycle, one of the most critical actions is to hold the handle grips firmly. This is essential because a flat tire can cause the motorcycle to become unstable or hard to control. Firm grip helps the rider maintain better control over the bike as it begins to deviate from its normal handling characteristics. This control is particularly crucial during deceleration and any maneuvering that is necessary to safely bring the motorcycle to a stop.

In addressing the other actions, while applying the rear brake might seem like a logical response to slow down, doing so immediately can potentially cause the bike to skid or lose control, especially with a flat tire. Gradually decreasing speed is generally advisable, but the most immediate action involves maintaining control of the handlebars to manage the bike effectively. Lastly, straightening out the handlebars excessively can also be detrimental, as it can lead to loss of steering stability and further complicate the rider's ability to handle the situation. Therefore, a firm grip on the handlebars remains the foundational technique for managing a flat tire effectively.