Just how hard can your bike brake?

See if you can believe this. I was at a track training day a few years ago, and the chief instructor explained in a classroom session that the next track outing would focus on using the brakes hard. On hearing this, two people who had introduced themselves as RoSPA trained and IAM observers went into a huddle, and then announced: “We’re not happy about this.” It turned out that they had been taught not to brake, on the basis that they should always ride in such a way that stopping quickly would be unnecessary. But that wasn’t the half of it. They’d also been taught that braking hard was dangerous! In the awkward silence that followed I suggested it wasn’t as dangerous as getting impaled on the oncoming prongs of a combine harvester. Perhaps that was a bit tactless.

In fact, it’s not just the fundamentalists who can’t brake hard. Lots of people can’t, because they never practice. And braking a motorbike demands practice because, unlike stopping a car, it’s really difficult. On pre-ABS bikes you have to get near the limit while avoiding wheel lock. On ABS bikes you have to summon the nerve to get the ABS working in the first place.

The hardest you can brake, on a decent sportsbike, adventure bike or naked, is at a rate of about 1g. That means stopping from 65mph in three seconds. Next time the roads dry out, find an empty stretch and see how good you are. Count the seconds in your head, or say something that takes that long. If you ride a custom bike, you’ll need about 3.5-3.7 seconds, because its lower centre of gravity pushes the front wheel along, inducing lock-up. A sportsbike or naked carries its weight higher, so it pitches forward more, and so allowing more braking force to be applied. The reason you can’t exceed 1g by much is because you are already putting all the bike-and-rider weight onto the front wheel. Any more will send you over the bars.

Racers do rather better, hitting 1.6 or 1.7g. That’s because they brake while sitting up at 190mph, at which speed the sail effect of their body provides the extra stopping power. By the time they get down to 100mph or less, they’re stuck with the same physics as the rest of us.