Originally Posted by cubewheels

Wow, is yours an old model bike? Looks like new. Yes, the caliper rim brakes on cheaper bikes tend to be weak, unless it's V-brake.

Cheap mechanical disc or V-brakes still gives strong braking. The only problem with cheap mechanical disc brakes, is the dangerous and unpredictable "unsqueeze" behavior when the caliper bearings leave the slots (you suddenly lose the brake without warning).

All the cheap Walmart quality all-mechanical disc brakes have the same problem. There is of course a simple solution to the problem, the caliper housing should be adjusted so the side with the lever is much closer to the disc rotor and replace the brake pads when the lever arm is only 20mm away from the barrel adjuster when you press the brake lever to apply the brakes. Also buy the thickest replacement pads you can find.

Not sure if the mechanical Shimano disc brakes have the same problem but pretty sure the full hydraulic or mechanically actuated hydraulic caliper disc brake should not have this dangerous problem.