I suspect the metal at the valve hole also. I've never had such an issue as the Mavic rims I've been riding for the last 23 years came with plastic stem hole grommets so they could be used with either type of valve. Presta valve stems fit in very snugly, no play. Thus, enlarging the hole to Schrader and using the plastic grommets is always an option. The plastic grommets are slotted also, allowing them to expand as the presta valve must literally be pressed in, that's how good of a fit they are, as least the ones Mavic uses.
If you try to deburr the presta hole first, a rotary tool at low speed with a tapered sanding bit ought to work well, as well as countersinking drill bits. Like these from HF ! https://www.harborfreight.com/power-tools/drill-driver-bits/woodboring-bits/countersink/countersink-and-deburring-tool-set-3-piece-61629.html I think even if I did that I'd still do the suggest double stem nut idea to hold it in place. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/739dae3f-aa80-4c6d-bb0f-faa11715439en%40googlegroups.com.
