Comment by david-gpu | Hacker News Reader

Comment by david-gpu | Hacker News Reader

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Braking while turning is a risky business indeed. You typically want to use both brakes at once to reduce the chance of skidding, but if you do lose grip on either wheel nonetheless, you better have quick reflexes and release both brakes.

Sheldon Brown talked about this [0]:

> Skilled cyclists use the front brake alone probably 95% of the time, but there are instances when the rear brake is preferred: slippery surfaces, bumpy surfaces, front flat, broken [front brake]

> When leaning in a turn, traction is shared between braking and turning. Using both brakes together reduces the likelihood that one wheel or the other will skid and dump you. The steeper you lean, the less you can brake, so moderate your speed before a curve. When you are leaning deeply, you need to release the brakes entirely.

> Using both brakes together can cause "fishtailing." If the rear wheel skids while braking force is also being applied to the front, the rear of the bike will tend to swing past the front, since the front is applying a greater decelerating force than the rear. Once the rear tire starts to skid, it can move sideways as easily as forward.

I broke some ribs a couple of years ago on a downhill trail due to fishtailing. I should have dismounted, but I had not realized that the surface had turned from gritty to muddy.

[0] https://sheldonbrown.com/brakturn.html

What he names "fishtailing" is what is known as "highside" in motorbike circles. When the rear wheel loses grip, it and the entire frame except the front fork moves sideways. When the rear wheel inevitably retains grip, the resulting force violently flips the whole. On a bicycle this is rare and survivable, on a 200+kg mc not very much so.

In a turn you either apply energy if that is at all possible (usually), or just steer. It is recommended to accelerate inside a turn, because that way you can better control grip on the rear due to not accidentally engine-braking (not applicable to bicycles), and because thrust on the rear wheel helps the bike into the turn (applicable to bicycles).

Braking in a turn is a last-effort thing, taken only if you are certain that it'll lessen damage from otherwise imminent crash.

Biking is traction/grip control at all times. Traction is always shared between steering and brake/accel. You do not want less control in a turn, and loss of traction means loss of steering.

So you do not ever brake in a turn.

You decelerate on a straight before it. If a turn goes bad for whatever reason, that means that a) you made a mistake entering it at the speed you did, and b) now you choose what to crash into, and then execute the crash while hoping that your protection holds, which might include hard front brake and a steering input so that you lowside feet (and bike) first into the obstacle. But not before.

So the first lesson of bike-riding is being aware at all times of available traction.

95% use of fronts follows: you only use them on straights, and there they are much more efficient than rears because the whole mass of you and bike enhances front wheel traction. cf. the wheelie.

I would separate cycling from riding motorbikes entirely. They are different enough in terms of mass, speed, and especially acceleration.

As an example, pedaling while turning is often a bad idea because of the risk of pedal strikes, so acceleration inside a curve is often out of the question. And braking obviously reduces the grip available for turning, so braking while turning is only done in an emergency situation. But if you are going to brake while turning, using only the rear brake is suboptimal on a bicycle.

And you don't normally need to consciously countersteer on a push bike because of some combination of 1) lower speed and 2) much higher body mass relative to the bike, but countersteering is absolutely essential on a motorbike

Countersteering is important on a bicycle too when you need to quickly dodge something, for example. But yeah, the stakes around riding are so much higher on a motorbike.

On a bicycle if you can modulate the brakes so it never loses grip and you adjust your balance you can use both brakes in corners - I’ve been doing it most of my life, sometimes at speed and have done it on extremely steep slopes to avoid trees and obstacles. It’s possible without the rear wheel being on the ground at all, just never lock up or lose traction on the front wheel but that takes (sometimes painful) practise.

It doesn’t feel as good as decelerating before, and is most definitely not as safe as you clearly explained.

Well, IF. If you have enough skill you can a do stoppie in a turn, turn around and shoot off the way you came from. But this is bordering on stunt riding, not something to be relied on for day-to-day riding where you have to have enough margin to account for being not very focused, road having various low-friction crap that fell off a truck, crazy pedestrians, car drivers asleep etc.

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