Thanks for reaching out. Depends on the liquid ballast that you use. Some can be used with the original valve stem and some require heavy duty ones (metal based). Its not that the liquid won't pass through when filling its more that it will break down the rubber over time and could end up leaking around the stem area. Honestly, if you've already filled them I would just run them and you should be fine. Most modern liquid ballasts are beet juice based and much less harsh on rubber. Hope this helps.
