Can I shim this?
 

Hi,

I have a quill stem and the bars are about 25.7/25.8mm at the clamp point, I want to fit some 25.4mm flat bars into the stem.

Would it be ok to shim this?

Thanks

Daven

yes.

Yes, but far far safer to get the correct parts

Properly shimmed (0.2 mm shim wrapped around the bar) safety should not be an issue but noise might be. Sleeved bars tend to creak and these might too.