The Azerbaijan Grand Prix at Baku was a disaster for Mercedes’ Lewis Hamilton (and, well, for Mercedes in general). The reigning Formula One World Champion looked set to take the lead at one of the late-race restarts… until he went sailing off the racing line into the run-off zone. Hamilton lost out on his chance to scoop up a crucial win, instead taking home a measly 15th place. It all comes down to a so-called “magic button.”

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A magic button definitely sounds like the kind of thing that would be banned about as quickly as it was introduced in our modern day, highly regulated motorsport world.

Basically, that magic button offers a little bit of extra help on starts and restarts by taking advantage of hybrid-era rules. So, things are more complicated now than just pressing the brake pedal and having the hydraulic brakes respond. Instead, part of the braking is done by squeezing the brake discs, which offloads kinetic energy as heat and slows the car. The other part of the braking comes when the hybrid system sucks up some of that energy to store in the car’s battery, which in turn slows the car down. It’s the same principle as one-pedal braking in electric cars.

It can be a little complex, so I’ll give you a little visual of how things are done:

Drivers now get to adjust how much braking power comes from the energy harvesting, alongside the more traditional adjustments of wheel-to-wheel brake bias.

The magic button is one way of mapping that brake bias. In this case, it moves the brake bias more toward the front of the car than you’d want for normal racing, and it also completely eliminates energy harvesting, so it’s a front-loaded, mechanical braking situation.

That, in turn, means the front brakes and tires stay within an optimal temperature window, even during safety car periods that would normally cool the brakes and tires. Press the magic button while following a safety car, and it’s almost like you never slowed down from speed.

You just need to make sure that particular setting is no longer active when you’re, y’know, attempting to turn into a corner. All that frontward brake bias means those brakes are just going to lock up if you hit them too hard, which is generally what’s asked of drivers when they approach a first turn.

Hence what happened in Baku. Hamilton somehow reactivated the magic button (honestly, with all those dials and buttons and knobs, I don’t know how this doesn’t happen more often) just before or during the restart. When he went into the first corner, instead of taking advantage of all that sweet, sweet brake heat, he cooked the discs and slid off the track. Not exactly the ideal situation for someone aiming to defend his championship.

And that’s also why you’ll see the Mercedes team get shockingly good starts. They have a very ideal combination of settings that allows Hamilton and Valtteri Bottas to shoot ahead of the pack during some of the most crucial milliseconds of a race.

That magic button is also legal, by the way. Drivers adjust brake bias and energy storing at just about every corner of every race track. That’s part of what makes F1 racing so fun and so technical. Implementing a specific button to press that changes the brake bias is totally fine. It just might come with some unintended consequences.