New answers tagged inflation
If using a Presta valve this can be caused by having the stem nut done up to tightly (effectively trying to pull he stem through the rim) Not the case here, but maybe useful for future searchers.
If this issue persists (i.e. your tubes keep failing near the valve stem), then you likely have a "sharp" rim or burred valve hole. While you can try and file this down a bit, I've always found it simpler to get about 4cm x 2cm of old tube, cut a 5mm slice into it, and then push the valve through this. This will mean that you have tube => valve through old ...
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