Should You Downshift When Decelerating?
3 Answers
It is not a problem if you do not downshift when decelerating, but if the speed is too low and the clutch is not depressed, the vehicle may stall. Additionally, not downshifting after deceleration and then attempting to accelerate can cause lugging, which damages the transmission and negatively impacts both the engine and transmission due to the significant impact force, leading to potential harm. Therefore, it is advisable to shift gears appropriately based on the vehicle speed. Precautions for deceleration are as follows: Single-wheel passing over speed bumps: Many car owners choose to pass over speed bumps with one wheel, believing it reduces damage to one side. While this logic is correct, it overlooks the fact that all the impact force is borne by one side. Over time, this can lead to misalignment or deformation of the suspension, issues with wheel alignment, and tire wear. It is recommended to perform wheel alignment promptly. Diagonal passing: Diagonal passing is relatively straightforward—tilting the front of the car and passing over the bump sequentially. This method may feel less bumpy, but it causes uneven force distribution on the suspension system. Passing over speed bumps this way actually causes more damage to the springs and shock absorbers, and the car body also bears the force generated by the bump, making it not an ideal method. Dual-wheel passing: Dual-wheel passing is undoubtedly the best way to go over speed bumps. Although it may feel more jarring, both wheels contract and bear the force simultaneously, with the springs and shock absorbers sharing the load. Whether the suspension is independent or non-independent, it will not be significantly affected.
After driving manual transmission cars for so many years, I believe whether to downshift when decelerating depends on the situation. When gradually braking to a red light in daily driving, staying in the original gear is perfectly fine and actually more convenient. However, when encountering long downhill slopes or sharp turns, I definitely proactively downshift to use engine braking for more stable speed control. Last time on a mountain descent, continuous braking made the pedal feel spongy—that's when staying in 3rd gear proved much safer than coasting in neutral. What veteran drivers call 'emergency downshifting' refers to dropping two gears instantly in urgent situations, where the soaring engine RPM can immediately rein in the speed, far more reliable than relying solely on brakes.
I commute in the family's old manual transmission car, barely shifting gears during stop-and-go traffic in the morning and evening rush hours. However, there are two situations where downshifting is a must: first, when braking hard on rainy or snowy days causes the tires to slip—immediately downshifting makes you feel the car being gently held back; second, when crossing school speed bumps, shifting to second gear in advance and coasting slowly avoids harsh braking that might draw disapproving looks from parents, and passengers won't be jolted around. I remember my driving instructor saying that below 40 kph, you can be lazy about shifting gears when moving slowly, but if you need to stop suddenly at 60 kph, second gear combined with braking is the most effective.
