>>1779280important note is assembly faults as
>>1778912 mentions, many bikes meet an early death though poor assembly and adjustment. its kind of insidious
the next most common flaws in Material specification
really cheep twist grip shifters fail farely quickly, the nylon bushing inside of them can bind up and crack
cheep thumb shifters are made of a plastic that is not very impact resistant, so they may chip or snap off if the bike is handled roughly
bad indexed shifters really mess up the shift quality, a quick fix is to swap in friction thumb shifters, some of the solid metal friction shifters are quite affordable
1 mm thin stamped metal V brakes may not be so good at holding the pads securely, due to the spherical washers of the brake pad post being designed for a mounting surface around 5mm thick
the thin steel also flexes allot, this combines with the brake having a very thin Bronze bushing around the V brake boss, this wears out quickly, and is not well protected against water ingress, (V brake boss can rust)
in short the brake pads are not held in good alignment as they become subjected to load, so they will misalign and wear out unevenly, worst case the trailing edge of the pad may momentary come into contact with the tire
in addition to this problem is that some V brakes do not have very good mechanisms for balancing and maintaining the return spring tension
next wear item is tires they come with, idk maybe they contain too much silicon, but somehow they are hard and lack grip yet wear as tho they were a softer tire
some saddles are very vulnerable to damage, due to thin coatings or not being the right shape, or quite classic having holes poked in them by the brake levers of other bikes
and saved for last is bearings
