When the rear tire of a motorcycle momentarily locks up or skids during downshifting, it is often referred to as a "rear wheel hop" or "rear wheel chatter." This phenomenon can occur due to a combination of factors:
Engine braking: Downshifting involves shifting to a lower gear, which increases the engine's braking effect on the motorcycle. This can cause a sudden deceleration, especially if the downshift is aggressive or if the engine speed is significantly higher than the road speed.
Rear wheel traction: When the engine braking force suddenly increases, it can momentarily exceed the available traction of the rear tire, causing it to skid or lock up. This is more likely to happen if the road surface is slippery, such as during wet or icy conditions.
Weight distribution: During downshifting, the weight distribution of the motorcycle shifts forward, putting less weight on the rear wheel. This reduced weight on the rear tire decreases its traction, making it more prone to skidding.
Clutch usage: Improper use of the clutch during downshifting can contribute to the rear wheel hop. Releasing the clutch too abruptly or not properly coordinating the throttle, clutch, and gear lever can cause sudden and harsh engagement of the transmission, leading to a skid.
To prevent or mitigate rear wheel hop during downshifting, here are a few tips:
Smooth downshifts: Practice smooth and progressive downshifting, matching the engine speed (revs) to the road speed before releasing the clutch. This helps maintain a better balance between engine braking and rear wheel traction.
Rev-matching technique: Employ rev-matching, which involves blipping the throttle while downshifting to match the engine speed with the gear you're shifting into. This technique helps reduce the abruptness of the downshift and maintains smoother control.
Proper clutch control: Coordinate the use of the clutch and throttle to smoothly engage the lower gear without causing a sudden jolt. Gradually release the clutch while adding throttle as necessary to maintain a controlled and balanced transition.
Road conditions and braking: Be mindful of the road surface conditions, especially when downshifting during slippery conditions. Apply gentle and progressive braking rather than relying solely on engine braking to prevent rear wheel skids.
By practicing smooth downshifting techniques, utilizing the clutch properly, and considering road conditions, you can minimize the occurrence of rear wheel hop during downshifting and maintain better control over your motorcycle. It's also worth noting that different motorcycle models and tire types can exhibit varying levels of rear wheel hop, so familiarity with your specific motorcycle and its characteristics is essential.