Q: is it better to use flat ring or knife ring for mountain bike

A: I'll give you some parameters if you like! It's better and harder to use the circle, but it's not suitable for climbing. Ordinary circle can be used for any purpose. Now the more common mountain circle is single layer, double layer circle, and knife circle and flat circle

Is 30 circle mountain bike good or 40 circle mountain bike?

Answer: the higher the knife is, the better the rigidity and inertia are. The harder it is to climb the hill. Usually, the knife circle is not used. The speed is increased. Generally, there are few mountain bikes for road vehicles