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CarBack pairs with your Garmin Varia rear-view radar and announces approaching vehicles through your iPhone speaker or Bluetooth headphones. When a car approaches from behind, you hear "car back, 45 meters." When it passes, you hear "all clear." No Garmin head unit required.
Open CarBack, tap the gear icon to open Settings, then tap "Pair a Varia radar." Make sure your Varia is turned on and within a meter of your phone. Once paired, CarBack auto-reconnects on every future ride.
CarBack supports Garmin Varia models with Bluetooth Low Energy: RTL515, RTL516, RVR315, eRTL615, and RCT715. The older RTL510 and RTL500 use ANT+ only, which iOS doesn't support.
Yes. Bluetooth Low Energy supports multiple simultaneous connections. Your Varia can stay paired to your Garmin head unit while CarBack connects to it — both work at the same time.
No. CarBack connects directly to your Varia radar over Bluetooth. If you have a Garmin Edge, keep using it — CarBack adds voice alerts on top. If you don't have a head unit, CarBack gives you audio-only radar awareness through your phone.
When a vehicle approaches from behind, CarBack speaks "car back" followed by the distance in meters (e.g., "car back, 85 meters"). When all detected vehicles have passed, it announces "all clear" after a few seconds. You can also switch to tone-only alerts in Settings if you prefer beeps over voice.
The distance comes directly from your Varia radar and is announced in 5-meter increments. The Varia detects vehicles up to about 140 meters behind you. Distance accuracy depends on the radar — CarBack reports what the Varia sees.
You can choose between two sensitivity levels:
Yes. Each distinct vehicle detected by your Varia triggers its own alert. If three cars approach in a group, you'll hear three announcements.
No. CarBack is a backup alert layer, not a replacement for your mirror, head-checks, or Garmin head unit display. Alerts may be missed, delayed, or fail silently. Always ride as if CarBack isn't there.
Any Bluetooth headphones paired with your iPhone. AirPods, Shokz, bone conduction headsets, and helmet speakers all work. You can also just use the phone speaker.
Use headphones that don't block outside sound — you need to hear traffic. Good choices:
Avoid noise-canceling or sealed in-ear headphones while riding. Some US states restrict headphone use on bikes — check your local laws.
Yes. If no Bluetooth headphones are connected, alerts play through the phone speaker. Mount your phone on your handlebars or keep the volume up in your jersey pocket.
CarBack uses a playback-only audio session that mixes with other apps. Music and podcasts should continue playing, and CarBack alerts will play over them.
Yes. CarBack maintains its Bluetooth connection and plays voice alerts even when the screen is locked or another app is in the foreground. Put your phone in your pocket and ride.
CarBack uses Bluetooth Low Energy, which is very efficient. Battery drain is minimal compared to GPS-based cycling apps. The "Keep screen on" setting in CarBack will increase drain — turn it off if your phone is in a pocket.
CarBack reads your Varia's battery percentage over Bluetooth and shows it on the main screen. Check it before you ride so you don't start with a dead radar.
CarBack uses Bluetooth Low Energy to communicate with your Garmin Varia radar and to route audio through Bluetooth headphones. Without Bluetooth permission, the app cannot connect to your radar or use wireless headphones.
Check these things:
This means CarBack lost the Bluetooth connection to your Varia. It will auto-reconnect when you're back in range (typically within a few meters). If your Varia is nearby and it still shows out of range, try closing and reopening CarBack.
No. No accounts, no servers, no analytics, no tracking. CarBack connects directly to your Varia over Bluetooth. Nothing leaves your phone. See our Privacy Policy for full details.