For those who use tubes with removable valve cores here's the perfect tool. If I find that a tire has a very slow leak it's usually the valve core that needs a little tightening.
|Park Tool VC-1|
|The plastic piece at the top of the picture is what I used in the past to tighten valve cores. It would wear out fast.|
The VC-1 is designed for both Presta and Schrader removalble valve cores. The notch in the middle is for Presta stem extensions.
|The VC-1 fits nicely between the spokes. The VC-1 on the valve core the core can be easily tighten by hand.|