Why are folding bike warranties so short? I am looking for an affordable  folding bike with reliable warranty.  So far all the bikes I looked at have 2 weeks to 3 months warranty for frame and manufacturers warranty for parts, nothing like 5 years to 10 years warranty for their fixed frame counterparts. Why are folding bike warranties so short?
Sounds like you're looking for opposing features.  A good/great folding bike will cost more than the equivalent full-sized bike.

A cheap folding bike will have the bare minimum warranty permitted in your location.

For example, the warranty on a Giant bike is


  LIMITED WARRANTY
  Giant warrants for the original owner only the frame, rigid fork, or original component parts of each new Giant brand bicycle to be free from defects in material and workmanship for the following specified periods:
  Warranty of lifetime for - The bicycle frame, except on models intended for downhill purposes.
  Warranty of ten years for -  Rigid forks.
  Warranty of three years for - Frames on models intended for downhill purposes.
  Warranty of one year for - Paint finish and decals
  All other original parts, including rear shock linkages, but excluding non Giant Brand parts, suspension forks and rear shock absorbers. (All non Giant brand parts, suspension forks, and rear shock absorbers shall be covered exclusively by the stated warranty of their original manufacturer.)


Their only folder is $819 NZ or about $600 USD.



By comparison a top folder like a brompton has a 5 year warranty on the frame, and only on material and manufacturing faults.  This will not cover accident damage or wear and tear.


  If your bicycle has a material or manufacturing defect, we will replace the defective part free of charge if we are notified within five years (in the case of a frame part) or two years (in the case of other parts) from the date of first purchase of the bicycle.


Their folders range from £800 to £2200, so $1100 to $3000 USD.

In short, you get the warranty you pay for.