By John S. Allen, CRW Safety Coordinator

Let's look into principles which support good braking skills.

Safest against skidding is no braking at all. The force vector (blue arrow) due to the weight of rider and bicycle extends directly downward from the center of mass. Its length is scaled here so that the weight takes it from the center of mass to the ground.

And the most conservative braking on a bicycle is with the rear brake alone. Using it alone is unlikely to result in a fall. The rear wheel may skid, but the front wheel continues to roll, and the rider can steer to maintain balance. Rear braking is weak, though. Using the rear brake alone can result in failure to slow or stop in time.

Why does the rear wheel skid?

The center of mass of bicycle and rider is high above the road surface. They want to continue moving forward but the force slowing them is down is at the road surface. So, braking places more weight on the front wheel and less on the rear wheel. When rear braking overcomes the reduced traction of the rear tire, it begins to skid.

Using the rear bake alone is the safe option though when riding on a slippery surface. That is, as long as you go slowly enough!

The blue force vector in the image below, as in the earlier image, represents the weight of rider and bicycle. The green vector is the force of deceleration due to braking. The red one is their vector sum, combining the downward force of gravity and the forward force of deceleration. This vector reaches the ground closer to the front wheel than the one from gravity alone, reflecting a transfer of weight from the rear wheel to the front wheel.

On a good, paved surface, rear-wheel braking lightens the weight on the rear wheel considerably, and skidding becomes a serious problem. A single stop can wear a flat spot in the tread of the rear tire. Long skid marks left by bicyclists provide ample evidence of this issue.

Those long skid marks also testify that the rear brake is very hard to modulate. To understand this, it helps to look into how friction works.

Skid marks at a Chicago intersection. The right-hook threat here is grist for another article! 

Sliding vs. static friction

Braking is about friction, of two kinds: sliding and static. Sliding friction is only about 70% as strong as static friction. So, when a wheel goes from rolling to skidding (static to sliding),braking decreases by about 30%. 

The tire must re-establish static friction to get rolling again. At the same time, to allow the wheel to turn, the brake must go from static friction to sliding friction. The two effects, together, require about a 50% reduction in brake-lever force to get the wheel rolling again. When it does start rolling again, braking is only half as strong.

Reducing force on the lever slightly would intuitively seem to get the rear wheel rolling, but it does not. Reducing force on the lever by half, then restoring it to nearly what it was before, is highly counterintuitive.The required rapid, precise control of the brake lever is impossible in practice.

Rear-brake bicycle culture

Just as with a rear hand brake, a foot-controlled rear brake -- a coaster brake -- is hard to control because of the static-vs.-sliding friction issue. A bicycle with a fixed gear -- no freewheeling -- gives more "road sense" than a coaster brake when the rider is pushing back against turning pedals, but the braking force rises and falls twice per crank rotation. At the top and bottom dead centers, there is almost no braking. The only continuous strong braking on a brakeless fixed-gear bicycle is with a "skip stop". The feet are planted on stationary pedals, the rear wheel skids and the tire wears out quickly.

Expectations about brake performance shape bicycle culture. Countries where coaster brakes are usual, or were till recently, have a conservative culture of slow riding and separation of bicyclists from motor traffic. Hipsters who ride brakeless fixed-gear bicycles go to the opposite extreme, addressing their poor braking performance through denial and risk-taking. Good use of dual handbrakes is more compatible with bicyclists' operating as normal road users. In any case, a bicycle should have two independent braking systems, because one or the other will fail sooner or later.

Two brakes

Conventional advice to bicyclists with front and rear hand brakes is to use the two brakes equally. So, now let's introduce the front brake.

Equal use of the brakes is usually safe. It can, though, skid the front wheel and result in a fall on a slippery surface or when leaning into a turn.

Equal force on both brake levers reduces stopping distance compared with use of the rear brake only, but braking still has to weaken substantially to take the rear wheel from skidding to rolling. 

Equal use of the brake does make the best sense on a long downgrade, so neither brake overheats. 

Front brake only?

It's heresy, but it's fine for moderate, straight-ahead braking on a good pavement and not riding into a slippery patch.

With only the left hand on a brake lever, you can shift a rear derailer or internally-geared hub as you slow down. This is very practical when approaching a stop sign or red traffic signal.

Anti-lock bicycle brakes?

A motor vehicle with anti-lock braking keeps each wheel rolling by using repeated, very brief skidding to test the limit of static friction. That is why the car shudders in hard braking. ABS also controls the level of braking separately on each wheel. For these reasons, a car with ABS can stop shorter than one without.

ABS on motor vehicles uses electronics to detect the rotational rate of the wheels. ABS is also available on motorcycles, and on some high-end e-bikes. A purely hydraulic system using pumps in the hubs might be practical on a pedal bicycle, but for now, that is just a thought.

A bicycle has braking advantages?

So, you might then ask, does the lack of ABS amount to total loss for bicyclists?

No. I count five compensating advantages of a bicycle:

• A bicycle only rarely attains high speeds typical of motor vehicles.

• Reaction time can be shorter with the hands covering the brake levers than with a foot that travels from the accelerator pedal to the brake pedal. 

• A bicyclist has an unobstructed view ahead, and no hood extending forward. 

• With dual brake levers, a bicyclist has separate control over the brake on each of the (only two) wheels.

• A bicycle’s short wheelbase and high center of mass set the limit to front-wheel braking at pitchover rather than skidding.

Four of those features make good intuitive sense, but is the pitchover threat also an advantage? 

The image below shows a bicyclist who has applied the front brake hard enough to raise the rear wheel. The blue force vector, as in the earlier images, represents the weight of rider and bicycle. The green one is deceleration due to braking. The red one, their vector sum, points ahead of the front-tire contact patch. If this vector reaches the ground ahead of the front wheel, as it does here, the rear wheel will rise. Only quick reflexes to release the front brake will prevent pitchover once this happens.

(The weight and combined vectors in the image do not reach the ground because they represent the same forces as in the earlier images, and the weight stays the same.)

Applying the advantages of bicycle brakes in hard braking

Well, the situation looks tough, but let's look at the advantages one by one and see how they can work for you.

The first advantage, lower speed, works even better than intuition would suggest.. At half the speed, perception and reaction distance is half as long. But braking distance is proportional to the square of speed, a quarter as long at half the speed. Even a bicyclist with only a rear brake has about the same braking distance at 15 mph as a car has at 25.

Shorter reaction time, unobstructed view, no hood -- all effectively reduce stopping distance

Separate control of the front and rear brakes can prevent overuse of the front brake, avoiding front-wheel skidding on a slippery surface. But overuse of the front brake still can result in pitchover.

But that pitchover risk can actually be an advantage! It allows safe use of the front brake much more strongly.

The front wheel will never skid in hard, straight ahead braking on a good, paved surface. As braking increases, more and more weight transfers from the rear wheel to the front wheel. When there is little weight on the rear wheel, only a very light application of the rear brake is enough to make it skid. Then, modulating the front brake easily adjusts the weight on the rear wheel enough to take it back and forth between sliding and rolling friction -- a useful signal to modulate the front brake.

This completely transforms the conditions for ABS, making human control possible. The modulation rate is within human abilities, using weight transfer of the entire bicycle-and-rider system, rather than rotational speed of the front wheel.

In hard braking, the weight on the rear wheel changes proportionally much more than that on the front wheel. So, for example, if the front wheel goes from carrying 70% to 80% of the weight of bicycle and rider, that is an increase of 14% in weighting. Meanwhile, the rear wheel goes from carrying 30% to 20%, a 33% decrease. 

With light weight on the rear tire, skidding wears it only lightly. Braking this hard is in any case needed only for emergency stops.

How to be human ABS

Increasing braking safely up to where most weight is on the front wheel does take a second or so. For that reason, using the rear wheel's signal to modulate the front brake is practical only at higher speeds. At low speeds, it is necessary just to know how hard it is safe to apply the front brake. The amount of deceleration felt through the arms provides a clue. Braking distance is in any case much shorter at low speeds. Pitchover is slower, too. so it is possible to get the rear wheel back down. It should be second nature to release the brakes whenever the bicycle starts to go out of control.

For a bicycle with dual handbrakes in good condition and an expert rider, on a good, dry paved surface, maximum deceleration, about 0.5g, is achieved mostly with the front brake. (One g is the force of gravity.) For a car with ABS, maximum deceleration is about 0.8g. So, at any speed, the bicycle has about 1.6 times the braking distance. That translates, though, only to a bicycle’s having the same braking distance when going 60% as fast as a car, say 18 mph instead of 30.

The image below shows a bicyclist at the limit of braking short of pitchover. The vector sum of weight and deceleration is at the front-tire contact patch. The force from deceleration is about half the force of gravity, 1/2 g. The rider could improve this somewhat by sliding back on the saddle, though the forward location of the brake levers on this bicycle with drop bars makes that option less practical than on a bicycle with flat bars.

Direct, mechanical control to release the front brake when the rear wheel lifts has been invented and reinvented repeatedly, and is currently (2026) available on at least one brand of children's bicycles. I have not tested it myself.

Condition of the machine

It should be needless to say, but good braking requires the brakes to be in top condition. Braking needs to be smooth and even. A rim spread wider by a pothole impact should be replaced. Brakes wear and need adjustment, unless they are self-adjusting hydraulic brakes, which need frequent inspection because they offer no sign that they are worn out. A brake lever should not go all the way to the handlebar. But also, the brake should engage when the lever is depressed only slightly, so it is not a "jiu-jitsu" lever where nothing happens till the lever is halfway to the handlebar, then it grabs, and you skid or go over the handlebars.

Handlebar choreography

In the USA, it is standard for a bicycle's left brake lever to operate the front brake. The conventional explanation is that most people are right-handed and the right hand is stronger. That makes little sense. People manage to play musical instruments using both hands, after all. As already mentioned, it is convenient to shift down while using the front brake. And on an e-bike the throttle also is on the right

Most hand signals are with the left hand, but braking with only one hand on the handlebar is not a good idea anyway. In any case, hand signals are rarely necessary when braking. 

If you think of hand signals as communication rather than just announcements, you coordinate it comfortably with braking. A turn signal is usually a request to be let into line, when riding at a steady speed. Once the correct lane position is established, turning is usually obvious from lane position, or you are stopped and both hands are free. A slow signal usually serves to inform a motorist or another bicyclist that passing is unsafe; shifting is usually unnecessary then.

Stopping pedaling indicates that you are slowing (one more reason to keep pedaling on an e-bike unless you are slowing or stopping.)

Note however that the left-hand lever of a motorcycle operates the clutch, while the right-hand lever operates the front brake and throttle. If you also ride a motorcycle, you do well to switch the brake cables on your bicycle. Once good braking technique is burned into muscle memory, a machine with the front brake on the wrong side feels as if the brakes are defective!

More about braking from Sheldon Brown, who recommends operating the front brake with the right-hand lever. And it works differently in countries where traffic keeps left, too. Different spokes for different folks!