Bike brake no longer gripping – lever can be pulled almost all the way to the handlebar

With a rim brake, the most common cause is simply worn brake pads. Inspect the pads: if the grooves have nearly disappeared or the material is very thin, the pads need to be replaced. Fit new pads and align them parallel to the rim (angled very slightly toe-in at the front to prevent squealing). If there is still too much play in the lever afterwards, adjust the cable tension using the barrel adjuster at the brake lever or brake body. Also check whether the brake cable is frayed. Test the braking performance after every adjustment while stationary before riding.