fans ofFast and furiousThe franchise will likely be familiar with Vin Diesel’s iconic line, “Grandma shift, not double-clutch like you’re supposed to.” This has led many gearheads to start reflecting on their own driving and whether it was grandma shifts or dual clutches and whether the latter was really better. For most viewers, however, we struggle to understand any of these terms.
That’s why we wrote today’s blog, first to clarify the meaning and difference between these two terms.
Granny Shifting vs. double clutch
In simple terms, these two words refer to the way we shift gears in a car with a manual transmission.
This refers to the regular way we shift gears up or down in a manual car. If you learned to drive a manual car, this is how your driving instructor taught you to do it:
- Step 1: Press the clutch down
- Step 2: Shift up or down one gear
- Step 3: Start by lifting the clutch slowly while tapping the accelerator pedal
- Step 4: Find the “bite point” between the clutch and the throttle and once found, release the clutch and step on the gas harder.
This refers to a practice where you press the clutch twice when shifting between different gear ratios. Let’s say you’re shifting from third to second gear; the process looks like this:
- Step 1: Press the clutch down
- Step 2: Move shifter from 3rd gear to neutral
- Step 3: release the clutch
- Step 4: Tap the accelerator pedal
- Step 5: Press the clutch down again
- Step 6: Change from neutral to 2nd
The double-clutch method is only used when downshifting, as there is no point in accelerating the engine when changing gear (we will explain further below). But why go to all that trouble? Why not go with the tried-and-true “grandma shift” method?
Supposed Benefit of Double Clutching
The wisdom behind the dual clutch is apparently to “mesh” the gears and create a higher engine speed relative to the wheel and transmission speeds. The idea is that if the engine RPM is higher, you can downshift faster without losing speed. If you’ve ever downshifted while riding at any speed, you’ll notice pretty quick deceleration. If you’re double-clutching, you engage the clutch with the engine when it’s in neutral, but not the transmission, so you step on the gas and increase engine speed without increasing transmission or wheel speed.
So, was Vin Diesel’s character in the first “Fast & Furious” movie (2001) correct? Would his opponent, played by the late Paul Walker, have fared better in his run with Diesel’s character Dom if he’d grabbed twice? In short, no. We’ll deal with that in the next section.
Double clutch is a redundant exercise
While the technical theory behind double clutching as an advantageous move in a manual transmission isn’t entirely wrong, it is totally out of place in the movie. In the case of Diesel and Walker, the dual-clutch technique would not have suited him, as it is only really possible to use it when downshifting. For the film’s purposes, it’s just one more in a long line of examples of Hollywood getting things wrong; using legal terminology, even when it’s not remotely accurate. Whether or not anyone told the producers that they were incorrect in their claims is unclear.
More specifically, modern cars are equipped with special synchronizers that mesh the gears as well as the input and output shafts for you, creating smoother, more seamless shifts. It is one of the reasons why people who drive huge diesel semi-trucks have yet to master the dual-clutch technique, because many of these large trucks do not have synchronizers and therefore require the dual-clutch action to shift properly and smoothly. . Even this does not apply to all trucks, nor to all racing cars, but some use dual clutch even now.
An example of innovation that has made double clutching truly redundant is the constant mesh system and, even more recently, the Synchromesh system. The first is the most common type of system cars have, with each gear loosely connected to the drive shaft, allowing the gear to rotate at different speeds than the shaft. Synchromesh adds the split clutch with an all-new synchronizer hub and shifter sleeve.
Conclusion: Is dual-clutching bad for your car?
Some might ask the question, if our cars are now primed to handle the shifting mechanics required for smooth gear changes, can dual clutching really be counterproductive or harmful? The answer is no, not really. That’s the good news. You can try double clutching to see the technique for yourself without fear of damaging the transmission.
What’s important to remember, however, is that no matter what people say, the dual clutch will not provide any speed or competitive advantage.