I haven't had the issue personally, but here are a few things you might want to check:
1. **Tire Size Input**: Double-check that you've entered the modified tire size correctly in the settings. Sometimes even a small typo can throw off the calculations.
2. **Calibration**: Ensure that the unit is properly calibrated. Some devices will require a calibration procedure after changing tire sizes.
3. **Firmware**: Make sure your Trail Dash 3 is on the latest firmware. Sometimes updates can fix bugs or issues related to speed calibration.
4. **Resetting the Device**: If everything seems correct, try resetting the device to factory settings and re-entering your info. It might help resolve any glitches.
5. **Consulting the Manual**: Refer to the user manual for troubleshooting tips specific to speed correction issues.
6. **Reach Out to Support**: If all else fails, consider reaching out to the manufacturer's support for assistance. They might have additional insights or could help troubleshoot the issue further.
