Why Sometimes Caliper Brakes Fail To Release On One Side (ELI5 explanation)

Description of the Problem: The rider squeezes the brake levers to slow down. After reaching the desired speed, the rider releases the levers, but the brakes do not return to their idle position and continue to rub against the rim.

Potential Causes Of The Problem

  • Corroded Cable Housing

Caliper brakes are mechanical rim brakes controlled by a steel brake cable connected to a brake lever. When the rider squeezes the brake, the lever pulls the brake cable which in return pivots the brake arms towards the rim. The brake shoes then grab the rim and slow down the wheel.

For the brake to operate properly, its cable has to move smoothly. To achieve that goal, bikes use cable housing which has the following functions:

  1. Protect the cable from external stress and corrosion.
  2. Prevent friction between the cable and the bike frame.

In essence, the cable housing is used as a safe tunnel for the brake cable. Without housing, it will be impossible for the brake cable to operate properly.

With time, cable housing gets contaminated and wears down. As a result, it becomes harder for the brake cable to move inside the housing. The brake cable itself experiences wear and tear too.

The solution to this problem is to replace both the cable and the housing associated with it.

Tip: The fastest way to know if the problem comes from the cable or the housing is to disconnect the cable from the lever or the brake and then close the caliper with your hands.

If the caliper returns to its original position, then the problem is most certainly the housing and/or the cable. If the caliper remains closed, the issue lies within the brake itself.

  • Improper Cable Routing

If the cable routing has too many bends, the brake cable may fail to move smoothly even when the housing is new.

If the bike has been assembled by a reputable shop, this is unlikely to be the problem. But if the bike is coming from the second-hand market, the previous owner may have routed the brake(s) improperly.

  • Contaminated Brake Pivots
Dual-pivot Brakes

The brake arms of caliper brakes are pivoting around one or two fulcrums. If the brake has one pivot point at the center, it’s a single-pivot model. If it has two pivot points, it’s a dual-pivot type.

If those pivot points get contaminated, it can become difficult for the brake arms to return to their idle position upon releasing the brakes.

To rule out the pivot points as a source of this issue, it will be necessary to clean and inspect them.

  • Malfunctioning Return Springs
Brake Caliper Spring

Caliper brakes have a set of return springs made out of steel. They’re located right behind the brake arms. If they’re malfunctioning, the brake arms will fail to open upon releasing the brake.

The possible sources of the problem are:

  1. Broken springs. If one or two of the springs are broken or at least cracked, the return mechanism is completely ruined. In that case, the brakes are not safe to use and should be replaced. Replacing only the springs may cost more than a new set of brakes unless the user already has the needed spare parts.

Note: In general, brake springs are highly resilient and have a high number of cycles. However, they harden over time and in some cases simply snap in half.

2. Contaminated springs. If there’s lots of dirt (e.g., small stones, sand…etc.) on the brake, the contamination may prevent the springs from operating properly. In that case, cleaning the springs should resolve the issue.

  • Problematic Brake Levers

Another source of the culprit could be the lever itself. Mechanical brake levers are fairly simple and have a low number of moving parts. However, if the lever is dirty, the pivoting mechanism may be malfunctioning.

If the lever is the problem it will be quite obvious because the handle won’t return to its starting position upon depressing the brake. If that’s happening, it will be necessary to clean the brake lever.

  • Non-centered Straddle Cable

If the user is relying on center-pull brakes, then the straddle wire of the brake may be behind the defect.

If the straddle wire is not in the center, it may be pulling one of the arms off-center too. In that case, the affected brake arm won’t fully open when the rider stops braking.

To fix this issue, it’s necessary to readjust the brake.

Note: Modern calipers are side-pull brakes and do not have a straddle cable. Therefore, they won’t experience this issue.

  • Improperly Adjusted Brakes

Another source of the problem could be improperly adjusted brakes. If the brake arms are too close to the rim, the shoes may be rubbing against the rim even when the rider isn’t braking. This may create the impression that the brakes are not releasing.

Ideally, the brake shoes will be extremely close to the rim but never touch it. If this isn’t the case, a readjustment of the brake arms’ starting position is in order. This can be done either by playing with the barrel adjusters or by changing the location at which the pinch bolt grabs the brake cable.

  • Non-centered Brakes

Centering is the process of ensuring that both brakes shoes are at an equal distance to the rim. If that’s not the case, one brake pad will come in contact with the rim before the other. The result is subpar braking and uneven pad wear.

In some cases, a non-centered brake may create a constant rubbing of the brake shoe against the rim. It will feel as if the brakes are constantly engaged even though the rider is not using them.

If a brake is constantly moving off-center, chances are that it’s a single-pivot model. To mitigate the issue, people often switch to dual-pivot brakes which have a centering screw making it easier to balance the brake around the rim.

  • A Bent Rim

Rim brakes are very sensitive when it comes to wheel trueness. If the rim is slightly out of true, it may start rubbing against the brakes and create the feeling that the brake is catching the wheel even when the rider is not braking.

To fix this problem, it’s necessary to restore the roundness of the wheel. If the deviation is small, it’s possible to true the wheel by simply re-adjusting the spoke tension. If the actual rim is bent, the procedure is more complex and requires a complete disassembly of the rim.

Summary: What You Need To Know

If the brakes are not releasing, the possible problems are:

  • Worn and contaminated brake cables and housing.
  • Contaminated or malfunctioning pivot points
  • Contaminated or broken return springs
  • Seized Brake Levers
  • Improperly adjusted straddle wire
  • Poorly centered brakes
  • Bent Rims

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