People discover their dash cam has not been recording at the worst possible moment. Almost always the cause is the memory card, because a dash cam uses one far harder than any camera or phone ever will.
Why cards wear out
A dash cam writes continuously, filling the card and then overwriting from the start, all day, every day. Flash memory has a finite number of write cycles per cell, and a standard card reaches that surprisingly quickly under this pattern.
When cells start failing, the symptoms are files that will not play, recordings that stop early, or a camera that reports an error on startup.
Use a high-endurance card
High-endurance cards use memory designed for sustained rewriting and are usually marked for dash cam or surveillance use. They cost a little more and last several times longer in this application.
- Choose high-endurance, not just high-speed
- Match the capacity to your resolution; 4K needs more
- Buy from a reputable seller, as counterfeit cards are common
- Keep a spare, formatted and ready
Maintenance that actually matters
- Format the card in the camera every one to two months
- Check recorded footage plays back properly once a month
- Replace the card annually if the camera runs daily
- Replace immediately after any card error message
Formatting in the camera rather than on a computer matters, because it lays out the file system the way the camera expects.
Check the camera is recording
Get into the habit of glancing at the status light when you start the car. Ten seconds a day is what stands between having footage of an incident and not having it.
Reading the markings on a card
Card labelling is confusing because several different ratings appear together, and the one most relevant to dash cams is the least prominent.
- Speed class (C10, U1, U3): minimum sustained write speed. U3 for 4K.
- Video speed class (V30, V60): more reliable indicator for continuous recording.
- Application class (A1, A2): for running apps; irrelevant to dash cams.
- Endurance rating: often given in hours of recording. This is the one that matters.
A high-endurance card rated in thousands of hours will outlast a fast consumer card many times over in this application, even if the consumer card has better headline speeds.
Counterfeit cards
Fake memory cards are common, particularly through marketplace sellers. They report a large capacity to the device but contain far less real storage, and they fail as soon as recording wraps around.
- Buy from the manufacturer or a reputable retailer
- Be suspicious of a large card at an unusually low price
- Test a new card by filling it and playing back files from the end
- Check the packaging and printing quality against the manufacturer’s images
Capacity and how much you actually keep
Recording time depends on resolution, bitrate and whether a rear camera is sharing the card. As a rough guide at 1440p with front and rear, a 64GB card holds roughly three to four hours before looping, and 128GB roughly double that.
The practical question is how long before you notice an incident and save the clip. For most people a day’s driving is plenty, so 64 to 128GB is the sensible range. Going larger mainly helps if the car is used for long journeys or parking mode records overnight.
Frequently asked questions
Can I use the card from my phone or camera?
It will work briefly, but standard cards are not built for continuous rewriting and will fail far sooner.
Does formatting delete saved emergency clips?
Yes. Copy anything you want to keep off the card before formatting.
