Downshifting while braking at high speed on a motorcycle can carry certain risks and should be done with caution. Here are some potential risks to be aware of:
Rear tire traction loss: Downshifting while braking transfers additional engine braking force to the rear wheel. If done abruptly or in an uncoordinated manner, it can cause the rear tire to momentarily lose traction, especially on slippery or uneven surfaces. This can result in instability or a skid, potentially leading to a loss of control.
Front tire traction imbalance: Shifting gears while braking can momentarily shift the weight distribution of the motorcycle, placing more load on the front tire. This change in weight distribution, combined with the added engine braking, may affect the traction and stability of the front tire. It's crucial to smoothly and progressively engage the clutch and match the engine speed to the wheel speed to minimize this imbalance.
Rear wheel lock-up: Downshifting without proper rev-matching or blipping the throttle can cause the rear wheel to lock up momentarily. This can happen if the engine braking force suddenly exceeds the tire's ability to maintain traction. A locked rear wheel can lead to a loss of stability and potentially result in a skid or even a high-side crash.
Over-revving the engine: Downshifting at high speeds without properly rev-matching can cause the engine RPM to spike abruptly. This can result in over-revving, potentially causing mechanical stress or damage to the engine components.
To mitigate these risks, it's important to practice smooth and coordinated downshifting techniques while braking at high speed. This involves matching the engine speed to the wheel speed by blipping the throttle or employing rev-matching techniques. Additionally, maintain a firm grip on the handlebars, keep the motorcycle stable and balanced, and apply progressive and controlled braking inputs to maintain traction.
It's worth noting that downshifting while braking is a technique used in advanced riding scenarios, such as track riding or aggressive street riding. In normal street riding situations, it's generally recommended to complete your braking before downshifting to ensure stability and control.