Expert advice: why cold weather can make your brakes jam on

Brakes

There are certain car faults you associate with cold weather and brake trouble probably isn’t one of them. But in the recent spell of extreme cold weather Green Flag saw a dramatic increase in call outs to do with braking systems.

The number of cars experiencing calliper problems increased by 52 per cent. And drivers having trouble with handbrake cables was up by 77 per cent. Read on to find out how brake faults happen and what you can do to rectify them.

Why do brakes jam on?

When you stop driving, you invariably put the parking or handbrake on to ensure the car doesn’t move under its own steam. This generally engages the car’s rear brakes. When you’re driving, moisture gets between the brake part linked to the wheel (disc or drum) and the pad or shoe that works with it. In very cold weather, the moisture freezes when stationary for long periods, gluing the two surfaces together.

What exactly happens?

The majority of older cars and many newer small cars have drum brakes at the rear. These employ a pair of almost horseshoe-shaped shoes. When you push the brake pedal or pull up the handbrake, the high-friction pad within these shoes engages with the drum on the wheel. If there’s any moisture or other gunge in between the two, it freezes over time. Then in the morning it won’t release.

When there are brake pads and discs at the rear, it’s a similar story. Moisture between the pad and disc freezes. When you release the handbrake, the pads remain stuck against the disc. Alternatively, there might be moisture in the calliper that holds the pads and this too can freeze. But whatever happens, the result is the same: you won’t go anywhere.

 

A brake disc with the calliper (in red) housing the pads. These can get frozen to the disc in extreme weather

What about the handbrake cable?

As a failsafe, the parking or hand brake control is connected to the brake system by a different mechanism to the brake pedal. If the hydraulic brake system fails, this lets you still apply braking power to the rear wheels. In slightly older cars, the handbrake is linked by a cable. This can get moisture between the inner cable and the protective outer cable which freezes when the weather’s very cold. It means when you release the brake, the cable doesn’t move and the brakes stay on.

Thankfully, this should be less of a problem on modern cars. That’s because car makers have started fitting rubber gaiters to the cable to prevent moisture and dirt getting in and freezing.

What happens when you want to drive?

Depending on how frozen the brakes are, you may not go anywhere. And that’s when many of our customers call us. If the handbrake cable is frozen, it can be freed by pouring boiling water over it. However, you have to know where to pour the water for this to work…

Is there anything you can do?

Sometimes, gently trying to move the car forwards, then backwards will cause the brakes to release. They will do so with a heavy clunk which sounds horrible but isn’t anything to worry about. However, be careful. If the brakes don’t release almost instantly, the chances are they won’t do so without professional intervention. And if you keep trying to move a car with seized brakes, you could pull the friction part of the shoe or the pad off.

How can you prevent it happening?

Make sure your car is regularly serviced. That way brake fluid will be in tip-top condition, any torn gaiters or protection can be replaced, and some of the potential problems outlined above may be averted.

Scott Wilson is vehicle and customer data insight manager for Green Flag

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