mkwdrs

Just bought a Cannondale F7 Mtn Bike which I will use for 75% paved trail riding (with young son) and 25% light off road or beginner mtn bike trails. I like having a mirror to glance back and see if the 9 year old son is still tagging along or not when I am in front of him.

I was shocked to find that the inner diameter of the handlebars is too narrow to accept the normal bar end type of mirror. Is this the norm for mtn bike bars? I had an experienced mechanic attempt to install different types of mirrors and even he tore up 2 mirrors.

I assume that I will just need to get new bars. However, I don't want to do this if all mtn bike bars are this way. I don't like the helmet mirrors.

Any help appreciated.