Garmin have finally refreshed their best-selling Varia rear cycling radar, and on paper the new Varia RearVUE 820 brings some genuinely solid upgrades: USB-C charging, longer detection range, brighter lights, better battery life, and even vehicle type detection. But dig a little deeper and it’s clear this isn’t a simple generational upgrade. Depending on the bike computer you’re using, the experience can be very different, with many of the headline features locked to newer Garmin Edge devices. So does the Varia 820 set a new standard for cycling radars… or just a new benchmark for ecosystem lock-in?