I have those stems too. No problem with balance as the wheel/tire are balanced after the valve install. Don't think these will work with a tube though.

 

For the angled valve stems, does anyone know what size is best (8mm vs 10mm)? These are the two choices offered when I go to order.

 

Why they don't have them (90 degree) from the factory is beyond me. The stock stem is a bear to get to.

After about 6 years with my old bike, I FINALLY added a 90* stem when changing out the rear tire, and felt like an idiot for not doing it sooner.

 

I'll go measure today and let you know what I am using.

 

Caliper says the threaded part that goes into the wheel is 10mm. Hope that helps.