I know that some of the dashcams only record the few seconds prior to an incident.
But do the cheaper ones that record to a SD card, record continuously and fill the card quickly.
Some clips I have seen posted show footage that won’t have been triggered by harsh braking so I guess that those cams are recording all the time they are on. I wondered how long it take to fill a (e.g. 32gig) card and how often you need to wipe it.
Or do they record over the previous data?

I can only tell you how mine works. It stores 10 recording on the SD Card. It records 15 secs before and after and yes, it records over previous recordings. Its more than enough for a 15 hr day, to be honest thats all you need.

Mine records 1, 3 or 5mins clips continuously. When the card fills up it overwrites the oldest and keeps going. If you have an event that triggers the g-sensor (or you press the trigger button on the unit) it marks that file as protected and it won’t get overwritten

Thanks both of you.
I’ll have to do some more research on this.
Some of the clips I’ve seen from cyclists head cams seem to record everything rather than just incidents. and I wondered if that was common to cheaper units.