I plan on riding the Gap & C&O this spring on a hybrid with Freedom Racine Aero rims.They're 18mm wide with 13mm hook bead width.Does anyone know how wide a tire I can get on these rims?

Thanks,
McGrog

At least up to a 32mm, as this is a factory spec here https://www.diamondback.com/bikes/per.../insight-3-10/ more the point, what can your frame / forks take, as a lot of frames & forks are limited to a max width of tire, more so on road bikes, but hybrids can also have this limitation.