First of all, make sure that the axis of the carriage, connecting rods, as the left and right are not "Backlash". Cables switching speeds have the same tendency to wear that and brake cables. However, the main cause of attrition ropes, and thus reduce the reliability of the whole bike in general is incorrect adjustment mechanism for changing gear. Therefore, you should conduct health check switches speeds, trying to switch to all stars. If the chain jumps from extreme stars jerks or jumps, you should adjust the switch mechanism. When switching speeds – change must be carried out instantly and without grinding. And finally, check the reliability of fastening seat and steering wheel.
It should not be too tight, tighten the bolts enough to seat or steering wheel does not rotate at not too much effort. If the brakes are adjusted correctly, the full braking is carried out even at lever brakes just before the middle of its full speed. If it is not – it's a malfunction. Even in the case when the brakes are adjusted correctly, you should pay attention to brake pads. They should not have signs of wear, be free of potholes and have a gap between the rim and pads, at least 1 millimeter. Brake cables are usually worn in places of tension rope and mounting points. Make sure that these places are in the rope normal state. Also check the tension of the rope – it should be tight without excessive tightness, but without sagging.