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Courtesy Race Access (No further reproduction or commercial usage)
This is the first in a series of inside features from the Marlboro Yamaha Team examining the intricacies of the world's fastest race bikes
BRAKING
Braking is one of the most crucial aspects of racing, since it affords the best opportunity for overtaking at most racetracks. It's also very tricky, as Marlboro Yamaha riders Max Biaggi, Carlos Checa and their crew reveal ...
The act of braking is probably the most violent part of riding a 500 GP bike. The high-tech carbon brakes and slick tyres used on Biaggi's and Checa's Marlboro Yamaha Team YZR500s enable incredibly late and hard braking, to the extent that the uninitiated would find themselves getting thrown forward over the handlebars onto the front wheel.
 Obviously this doesn't happen to the pros, who train heavily to build the upper body strength necessary to maintain control during even the heaviest braking, but it underlines the hugely physical nature of this aspect of racing. A rider can pull up to 2g at the point of maximum stopping power, and remember he's not held in place by a four-point harness, like a car racer. Instead almost his entire body mass is thrown onto his wrists, amplified by g-force to, say, 120kg, while he digs the soles of his boots into the bike's footpegs to help himself stay onboard.
"Braking is some of the hardest work a rider has to do on a 500," says Checa's crew chief Mike Webb, a former racer. "They get a lot of g stopping from high speed and it would be more but we're limited by weight transfer."
Not surprisingly, the aim of every rider is to brake as late as possible for every corner. But there are many compromises he has to make to ensure the smoothest, fastest passage through a turn and ultimately, as always, he is constrained by the laws of physics.
In theory, riders can brake later than they usually do, but they would then struggle to get around the corner smoothly and their overall lap times would suffer as a result. The aim, therefore, is to brake as late as possible, while keeping the bike under control for a smooth entry into the corner, good mid-corner speed and a rapid exit onto the next straight.
"You can always brake later," agrees Checa. "But when you brake too late there's so much weight transfer to the front that the bike won't want to turn, and the front tyre starts to push (slide). Usually you test the limit during practice, braking later and later until you find that point at which the front pushes and you can't keep the bike rolling the way you want, then you back off a bit from there."
Of course, there are times when a rider has to sacrifice that smooth corner entry. If he's trying to out-brake a rival, who is already braking as late as he dare, he will have to take the risk of entering the corner less than smoothly, but so long as he can keep a tight line through the turn and stay ahead of his rival, the move pays off.
"When you're fighting with other riders you have to do that," says Biaggi. "You may end up entering the corner slower than usual, but you're ahead and that's what matters! Passing someone on the brakes is one of the best feelings, especially if you plan it for the last corner and make it work. The big thing about braking is working with your engineers to make the bike as stable as possible."
Weight transfer is the big deal in braking. When a rider hits the brakes hard, weight is thrown forward until the rear wheel leaves the ground. At this point the rider has reached his machine's maximum braking potential, since the bike will attempt a forward loop if he brakes any harder. An engineer's aim is to keep that weight transfer under control.
"You can brake later if you have a bike that is stable on the brakes," Biaggi continues. "But like most other things, it's a case of compromise."
Marlboro Yamaha Team manager Geoff Crust is the man in overall charge of the efforts of Biaggi and Checa and he fully understands the importance of braking.
"Getting the bike stable on the brakes is always a priority because the riders know this will be a big advantage in race situations," he says. "We spend a lot of time on this but you always have to careful. You can optimise a bike's set-up for braking but the problem is that this game is all about compromise and if we make the bike perfect for braking, it won't be so good at turning or changing direction, so there's a limit to what we can do."
Crust and his engineers juggle steering geometry and suspension settings to give their riders the best possible stopping performance. It's a far from simple task because every rider has a different braking style, and that changes from one GP to the next, according to circuit character, even from one corner to the next, as Biaggi's crew chief Fiorenzo Fanali explains:
"We always have to check the data recording because Max goes into some corners with the brake on and some without," says the Italian. "If he's struggling going into an important corner, where he goes in with brake, you have to adjust the suspension and chassis set-up to solve the problem, even though it might make the bike worse going into other, less important turns."
Ohlins suspension technicians Lars Isaksson works closely with the Marlboro Yamaha Team on all aspects of chassis performance, aiming to make the squad's YZR's the best brakers in GP racing.
"The kind of braking performance you want depends on the type of track you're at," says Isaksson. "If you're at a hard braking track, where you can make up a lot of time on the brakes, we set up the bikes for that and maybe the riders will suffer in other parts of the circuit. But I'd say most of today's tracks aren't all about heavy braking, so you try to get the bike so the riders can use a good corner speed and then exit corners as fast as possible."
Of course, once the engineers have done their work, it's all down to the rider. Getting a motorcycle stopped as quick as possible is a real art. Riders do the vast majority of their braking with the front brake, featuring two large carbon discs gripped by Brembo four-piston callipers. While old-school steel brakes required a full four-finger squeeze on the lever, carbons need just one or two fingers, allowing the rider to hold on and steer with the rest of his hand.
The front/rear brake ratio depends on the rider, the bike, the corner and the track conditions. In the dry there's little use for the rear brake, since the rear wheel is barely in contact with the tarmac during heavy braking, though more and more riders are starting to use a touch of rear brake to help tip into turns, literally 'backing' the bike in.
In the wet, riders will use more rear brake, since there's less grip available for full-on front-end braking, and they will also use more rear brake in other situations, for example on bumpier parts of a track, or where there is less grip. In other words they may use a fractionally different braking ratio for every corner on a racetrack! That's the kind of finesse that makes 500 GP racing the world's most awesome form of bike racing.
And how do riders know when to brake when travelling at 300kmh? "It is difficult at some places like Mugello, where you're doing over 300 when you arrive at the first corner," says Checa. "It's difficult to get a reference but I never use brake markers. You get used to where to brake during practice, so it's a mental procedure. You have a mental picture of when you need to brake and when you see that, you hit the brakes."
Next up in THE SECRETS OF 500 GP RACING: Cornering
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