The short answer
Pick a microSD card that is sold as high-endurance or video-monitoring grade, with a capacity matched to the camera and a speed class of at least U3 or V30 for 4K models. A dash cam is not a phone or a camera for holidays. It writes video non-stop, deletes the oldest files and writes again, thousands of times over. A general-purpose card is built for occasional writes and wears out under that pattern. The card is among the least expensive parts in the box and the part most likely to fail first, so it deserves a line in every purchase brief. This note gives the checklist; the dash cam SD cards page shows the 64GB and 128GB cards we bundle.
What "right" means for a dash cam
Four properties decide whether a card suits a dash cam. Endurance comes first, because the workload is a loop. Capacity comes second, because it sets how many hours of video fit before the loop starts overwriting. Speed class comes third, because a card that cannot sustain the camera's write rate drops frames or stops recording. Temperature tolerance comes fourth, because a windshield in summer is a hot, hard place for electronics. The table below turns those four into questions a buyer can put to a supplier.
| Property | Why it matters | What to ask the supplier |
|---|---|---|
| Endurance | Loop recording rewrites the whole card repeatedly | Is the card rated for continuous video recording? What is the stated endurance? |
| Capacity | Sets hours of footage before overwrite | Which capacity does the camera support? What is the maximum card size in the manual? |
| Speed class | The card must sustain the write rate | U3 or V30 marked on the card for 4K; Class 10 for 1080P |
| Temperature | Cabin heat shortens card life | What operating temperature range is printed on the datasheet? |
| Authenticity | Relabeled cards report false capacity | Where is the card sourced? Can a capacity test be run on a sample? |
Capacity: match the card to the camera
Capacity is not "bigger is better". Each camera has a maximum supported card size, printed in the manual and tied to the file system the firmware understands. Putting in a larger card can lead to a camera that refuses to format it or that reports the card as damaged. For most single-channel 1080P models, 64GB is a comfortable size. For 4K and dual-channel models, 128GB is common because two streams fill the card faster. The storage note shows the arithmetic: capacity in gigabytes divided by the bitrate-driven hourly rate. Larger cards also keep more locked event clips before you need to clear them, which matters for fleets that review footage once a week rather than once a day.
Speed class: enough, not extra
Speed class is a minimum sustained write speed, not a top speed. A 1080P stream at a moderate bitrate needs little, which is why Class 10 is the usual floor. A 4K stream at a higher bitrate needs more, which is why U3 or V30 is the usual floor. Paying for a faster card than the camera can use buys nothing, because the camera writes at its own rate. The speed class note explains the symbols. The practical rule is simple: match the class to the camera's resolution, then spend the rest of the budget on endurance.
Bundling versus letting the customer buy
If the card is not in the box, many customers will use whatever they have in a drawer. That card is often an old, small or heavily used one, and the first complaint of "the camera stops recording" lands on you. Bundling a known high-endurance card removes the largest single cause of early returns. It adds a line to the bill of materials and a barcode to the packing, but it also lets you state the card on the listing. The bundling note covers the seller side in detail, including how to word the listing and what to do about warranty.
What to write in a purchase brief
A brief that says only "64GB card included" invites substitution. A brief that names the properties leaves little room for it. Ask for the following in writing for each program:
- Capacity and class stated together, for example 128GB, U3, V30.
- Endurance grade - the card must be marked high-endurance or for video monitoring.
- Source - the supplier names where cards are bought and confirms they are new, not relabeled.
- Sample check - one card from the sample lot is tested for true capacity before bulk.
- Pre-format - state whether cards ship formatted in the camera's own file system.
The sample check matters. Counterfeit and relabeled cards report a capacity they cannot hold; the card appears to record fine until the loop reaches the false region, and then files vanish. A simple capacity test on a sample costs an hour and prevents that outcome. Sample routines are covered in the sample checklist.
Common mistakes buyers make
Three mistakes appear again and again. The first is buying on capacity alone, assuming that a larger number means a better card. The second is mixing card types across a fleet, so that one van has a good card and another has a worn one, and the footage gap shows up only after an incident. The third is skipping the formatting routine; a card that is never formatted in the camera accumulates errors. The format note gives a sensible interval. For fleets, a single specified card model and a replacement interval turn all three problems into a procedure.
How we handle it at the desk
Roadtrace is a sourcing desk, not a card maker. For bundled programs we coordinate with partner factories in Shenzhen to pack a high-endurance card with each camera, confirm the capacity and class in writing, and run a capacity check on sample cards. Terms such as minimum quantity and lead time are typical reference ranges and are confirmed in writing for each program; see MOQ and lead time. If you want a card specified into a quotation, send the camera model and target market through the quote form.