Q: “I’m currently reading Skip Barber racing school’s book “Going Faster” and came to the chapter about shifting. The author wrote that race cars usually don’t have synchros, and thus require double-clutch for downshifting. Since the book was written in the ‘90s, I’m wondering if it’s still true for race cars nowadays? Is it a required technique if I plan to develop my racing career in the future?”
A: Double-clutching is not needed, even in a non-synchro “dog” gearbox. Absolutely, heel and toe is, but there’s no need to double-clutch. Having said that, knowing how to do it does help a driver understand the reason and timing for rev-matching. But it’s not important.
For anyone reading this who are not familiar with double-clutching, here’s how it works: Approaching a corner where you have to downshift, you depress the clutch, move the shifter to neutral, let the clutch out, blip the throttle (rev the engine), depress the clutch again, move the shifter to the next lower gear, and then let the clutch out.
This technique was needed when downshifting in old cars without synchromesh transmissions, so unless you’re racing a vintage car, don’t worry about it. Even if you’re driving a car with a dog-ring (non-synchro) gearbox, don’t use it. But you absolutely need to rev-match on the downshifts, which requires heel and toeing.