How to Merge Wahoo and Garmin Ride Data

When Two Head Units Make Sense

Riding with both a Wahoo and a Garmin sounds redundant, but it's more common than you'd think:

• Backup recording — You keep the Garmin as a backup in case the Wahoo crashes or runs out of battery (or vice versa).
• Different sensor connections — Your power meter pairs to the Garmin via ANT+, but your heart rate strap pairs to the Wahoo via Bluetooth.
• Group rides — Someone in your group uses a different platform and shares their file. Now you have two recordings of the same ride.
• Switching devices — You just bought a new head unit but still carried the old one "just in case" on your first ride.

In all these cases, the best data is split across two files. Merging gives you one complete activity.

File Formats: Wahoo vs Garmin

Both Wahoo and Garmin use the FIT format for activity files, which means they store similar data in a compatible structure. This makes merging easier than cross-format merges.

Wahoo ELEMNT/BOLT/ROAM:

• Exports .FIT files via USB or the Wahoo app
• Records GPS, speed, cadence, heart rate, power (from paired sensors)
• Files available in the Wahoo app under activity history → export

Garmin Edge:

• Exports .FIT files via USB or Garmin Connect
• Records GPS, speed, cadence, heart rate, power, temperature, elevation (barometric)
• Files on device at Garmin/Activities/

The data structures are almost identical, making TrailBlender's merge process straightforward.

The Hard Way: Manual FIT File Splicing

Since both Wahoo and Garmin produce FIT files, you might think you can use Garmin's FIT SDK to decode, merge, and re-encode them. In theory, yes. In practice:

1. Install the FIT SDK — Requires Java and command-line familiarity.
2. Decode both FIT files to CSV — Each file produces multiple CSV tables (records, laps, sessions, device info).
3. Merge the record tables — Align thousands of rows by timestamp, picking the right columns from each file.
4. Rebuild lap and session summaries — These don't auto-update; you need to recalculate totals manually.
5. Re-encode to FIT — One invalid field or wrong message type and the file is unreadable.

This process takes hours and requires understanding the FIT protocol's message/field architecture. A single mistake produces a file that silently uploads with wrong data or fails entirely.

The Easy Way: Merge with TrailBlender

1. Export both FIT files — From Garmin: USB or Garmin Connect download. From Wahoo: USB or Wahoo app export.
2. Open TrailBlender and drag in both .FIT files.
3. TrailBlender identifies the overlap — Same ride, same time period, two recordings. The preview shows both tracks on the map.
4. Select your data sources — Pick the device with the best data for each channel:
   • GPS → Whichever head unit had better satellite reception (check the map preview)
   • Power → Whichever was connected to the power meter
   • Heart rate → Whichever was connected to the HR strap
   • Cadence → From the cadence sensor or power meter source
5. Preview the merged activity — One clean track with all sensor channels from both devices.
6. Export as FIT — Upload to Strava, Garmin Connect, or any platform.

Choosing the Best GPS Source

When both devices have GPS data, choosing the right primary source matters:

• Check the map preview — TrailBlender shows both tracks overlaid. The one that follows the road more smoothly is the better GPS source.
• Garmin Edge 1040+ with multi-band — If one device supports multi-band GNSS and the other doesn't, use the multi-band device for GPS.
• Mounting position — A stem-mounted device typically gets better reception than one mounted behind the handlebars or under an aero bar.
• Recording interval — If one device was set to "smart recording" and the other to every-second recording, prefer the every-second source for smoother data.