It depends on which cheap car based system you ate using. Most are not weather proof, and probably not very vibration resistant.

I'm using a Streetpilot 2820, which is weatherproof and which I've loaded non-Garmin maps to for touring Asia. But they were in the Garmin format.

That's an older model, but they often come up on eBay. The sticker with any car based GPS is finding a suitable mount that can take the pounding a bike gives especially on rough roads.

I've had mine from new, so the mounting hardware was easy to find.

The system has most mod cons including bluetooth, voice output and so on.

I've used a phone to navigate before, but that was an older Windows phone running Garmin software loaded on a card. If you go this route you will need a waterproof and vibration isolating housing, as well as sorting out the software / map choices.

Still probably the best unit I've tried is the Montana series. Expensive, but rugged, multipurpose, two battery options, map flexibility, easy to use, decent-sized screen and a lot more.
You can use it for marine/boating, outdoor and automotive purposes.

You may save a few hundred going with a cheap car unit, but once you sort out the mounting system and potential replacement due to rugged conditions, the savings may not be as much as expected.
And most of them are limited to vehicle use.


Sent from my chinaphone excuse the spelling