To be honest I have never even taken it into consideration when mounting tires. At the speeds I go I'd never notice. When I hit 45 or 50 on a trail it usually so rough that if the tire was way out of balance it doesn't seem to matter. Next time I mount a tire I'm going to set the mark at the rim lock and see if I can tell the difference. So longstory, short, the rim lock is way heavier than the valve stem.