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.

Have you try the mirror by Mirrycle? it will fit 5/8''-7/8'' ( 15.5-22.5mm) ID handle bars.

What mirrors have you tried so far?

I was using one of the Blackburn mirrors in some MTB-like handlebars -- it's the third one down, labeled the Multi-Mirror:
https://blackburndesign.com/mirrors.html

That and the Cateye BM-300G (https://www.cateye.com/en/product_detail/276 ) were the last two bike-mounted mirrors I used before I switched entirely to helmet mirrors.

I have to say. I put the Mirrycle mirror on my MTB. If it fits, Please get this. There is little to no vibration at all. I have a heafty fella with knobbies on my bike tires. Through Walking trails to the road the mirror image stays clears. VERY GOOD..>The Only downfall I had to build a stand so to speake to flip my bike over to lube the chain. No biggie though.