Bicycle brakes get better…mostly

by John Allen

Bicycle brakes have come a long way since the days of wooden-wheeled boneshakers with steel tires, but change does not bring perfection in this world.

Some history

Most early bicycles had only a fixed gear, or a spoon brake, which pressed on the tread of the tire. High-wheeler bicycles couldn’t benefit from a powerful brake anyway, as it would only pitch the rider forward from a high perch.

With the 1890s and the safety bicycle came the coaster brake, popular in the USA, Germany and the Netherlands, and rim brakes, most popular in the British isles. Coaster brakes were a major improvement over spoon brakes, but overheat on long downhill runs. So do all other hub brakes except for disc brakes and the very large drum brakes sometimes seen on tandems.

English three-speeds became popular in the USA following World War II, much so in the Boston area. These represented the first widespread exposure to hand-lever-operated rim brakes in the USA. But the long-reach sidepull brakes on steel rims of typical three-speeds offered poor leverage. The rims were as slippery as ice in wet weather, and prone to damage which made the brakes lurch and grab. I’m old enough to remember! My own first bicycles as an adult were three-speeds, and the braking ranged from marginal to terrible depending on rim condition.

Bicycling took a turn upward in the USA with the rise of the baby-boom generation, but fashion and marketing oversold the American bicycle market on imitation racing bicycles. The run-of-the-mill 10-speeds of the 1960s and the 1970s bike boom generally had good-quality rim brakes, but steel rims.

Only high-grade derailleur-equipped bicycles had aluminum rims until the 1980s, and wheel true had to be excruciatingly accurate for braking to be even, because the rims had angled sidewalls, and any departure from roundness made them wedge the brake shoes apart. French Super Champion Model 58 rims, the first common aluminum clincher rims with parallel sidewalls, first became available in the mid-1970s.

The mountain-bike phenomenon brought other changes in technology, not least with the widespread application of cantilever brakes, then direct-pull brakes and now disc brakes.

All-around advice

So, here we are now.

Any bicycle should have a rear brake capable of skidding the rear wheel (but to spare the rear tires, do it only briefly as a test). The front brake also should be powerful but you need to be careful in using it – more about that in another article. Operation should be smooth and predictable.

Cable failure – or loss of hydraulic fluid -- disables any brake – which is why every bicycle should have two separate braking systems, and brakes should be serviced from time to time. Anywhere a cable is repeatedly bent back and forth – on a brake lever, pulley or brake – it is like bending a paperclip back and forth. The cable will fail sooner or later. Cables should pivot where they attach, and the pivots should be kept lubricated. Cables should be replaced periodically.

Rim-brake issues:

• Brake shoes wear and need to be replaced periodically. But you knew that. They also need to be aligned carefully with the rims.
• Cable failure with a traditional cantilever brake will rotate the brake arms downward and outward and drop the transverse cable onto the tire. With a knobby tire, that will instantly lock the wheel, and if it is a front wheel, pitch the rider forward. A fender, reflector bracket, lamp bracket – something – needs to be in place to catch the cable.

A traditional cantilever brake without protection for the transverse cable. Tolerable with a smooth tire, but…

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Brake shoes of cantilever and direct-pull brakes (with the pivots on the fork or frame, closer to the hub than the rim) migrate downward as they wear. The brake shoes can dive under the rim and catch on the spokes. So, check alignment frequently.

A direct-pull brake (also called V brake)

Both brake shoes of a centerpull brake and the off-center pivoted brake shoe of a dual-pivot sidepull brake migrate upward toward the tire as they wear. Check alignment periodically to avoid a potential blowout.

A dual-pivot sidepull brake. One pivot is off-center.

A centerpull brake. Both pivots are off-center.

• Rim damage even with today’s better rims can result in a brake’s grabbing, resulting in a wear spot on the rear tire, or a pitchover in hard braking with the front brake.
• Carbon-fiber rims can’t take the heat, to the extent that the Union Cycliste Intenrationale has banned their use with rim brakes.
• Aluminum rims wear, especially in winter conditions or off road, and then air pressure in the tires splits the rim. If the braking surfaces of a rim have become concave, replace it. Many newer rims have a wear indicator – a groove or indentation which, when worn away, tells you it is time to replace the rim.

Disc brake issues:

Disc brakes are much preferable to rim brakes for off-road use in the wet and mud but introduced new issues. A disc brake stresses the front fork heavily. It can loosen a quick release and pull the front wheel out of the fork, or put a quick-release lever which opens too far into the rotor – leading to a Trek recall, but not only a Trek problem. A large percentage of CRW members is now riding bicycles with disc brakes, but I’ll make a case here for lagging behind the bleeding edge of progress. This way, other people, not you, get to experience early-production bugs. And they have happened.

You need to be very careful to check that the wheel is secure with a front disc brake. If the bicycle has a through axle – with holes rather than slots to secure the wheel in the dropout – good. That will prevent the wheel from coming out. Otherwise:

• Disc-brake pads and rotors wear. Pads should be checked and replaced as needed. If a rotor is significantly thinned, it should be replaced.
• The drawing below, from Trek, illustrates the problem with quick-release lever which can rotate backward too far, into the rotor. If your quick-release is like this, replace it – but see additional advice below.
• If the quick-release is of the exposed-cam type, replace it with an enclosed-cam one.

Exposed-cam quick release

A Shimano internal-cam quick release

• The quick-release surfaces that contact the dropouts should be of steel, and serrated. Shimano makes the best quick-releases, these days.
[ Caption Left_ one-piece aluminum quick-release adjusting nut Right: Aluminum adjusting nut with steel insert ]
• The hub also should also have serrated surfaces that bite into the metal of the dropouts. Avoid a front hub with smooth surfaces that contact the dropouts.
• If the front fork has carbon-fiber dropout surfaces, replace it. Carbon-fiber surfaces erode. Carbon-fiber lawyer tabs tear right off.
• Note the position of the quick release handle as you install the wheel. If it rotates bit by bit, you have a problem. It is loosening.
• On a bicycle with a front disc brake, check the tightness of the front quick release every time you get onto the bicycle.

More info

Be safe out there!