I just bought my 14" folding bike and I always getting a flat tire on the rear. It happened 4 times in a span of three days. 1st flat was with the stock inner tube, 2nd flat is with the new inner tube, 3rd same goes with 2nd. The mechanic advised me to change a bigger tire size from 1.75 to 2.25. 4th I thought it would solve the problem, rode longer than the old tire but still I got a flat tire. It's frustrating. I weigh 185lbs. Is that the reason why? But I've seen a lot of bikers who are bigger than me riding a 14 inch folding bike.
PS. They also added another rim tape.