I'm 191 cm tall and I want to buy UPTEN ZERO, the problem is the biggest frame size is "L" and is adapted for (173cm - 185cm) only, my question is it ok to ride a small bike? dose it effects me or what are the consequences? Thank you
Generally, it's not OK to ride a bike that is significantly too small for you, it's going to cause you problems.
Firstly, you may not be able to raise the saddle far enough to accommodate your leg length. You may find you are having to flex your hip joint too far which is inefficient and uncomfortable.
The handlebars will be too close to you, resulting in a cramped feeling and a riding position that is too upright.
You can replace the seat post and stem with longer ones but it's better to get a bike that fits you in the first place.