How To Install Free Maps on a Garmin Nüvi 255W Sat Nav

This blog post is about how to install free maps on a Garmin Nüvi 255W Sat Nav.

Introduction
A friend purchased an old sat nav via eBay and asked me to replace its 2010 UK map with a more recent map, as well as install a free map for Australia. I found an excellent site that provides free maps.

For the 255W I was able to replace the map on the internal memory, then have a second map on an SD card. I made sure both maps were selected via the settings. My friend went out for a short trip in the UK and used the device without any issues.

What follows is how I installed these maps on the device.

Warning: You are not to hold me or anyone else responsible for any problems you incur, including costs from reading this blog post, following instructions on this site or from downloading any files.

2nd Warning: You might want to just replace the map on the internal memory, and not use a sd card. I think you should reconsider and use the sd card method. If you don’t want to use a SD card, you won’t want to use all the instructions below, but please don’t forget to backup the device and make sure it is fully charged.

3rd Warning: I wasn’t in a position to test whether the map on the sd card worked, but it shows as being listed. I just used the new map that I placed on the internal memory.

NOTE: This how to guide has been written as much for me, as to help others! So it is aimed specifically at the 255W device, as well as having one map on a card and replacing the map on the internal memory. 

What you need:

• Garmin Nüvi 255W Sat Nav
• An external SD card
• USB cable

Optional:

• USB SD card reader (writer) *

* This is optional. If you turn off the 255W, insert an sd card and then connect the sat nav to a computer (such as a machine running Windows 10) via a USB cable, you can access the card’s memory. However I used an sd card reader instead and saved some battery life!

Step 1 – Update the device and charge
I wasn’t around for this step, but my friend might have updated the sat nav device to the latest version using the Garmin Express software. All I know for certain is that the software version I used with the 255W is 7.80, as shown in the screenshot below.

Also the software version is shown on the device. If you’re running a version of software earlier than 7.80, you probably should update the device.

It is important before you continue, that you charge the device as you wouldn’t want to have a battery issue during the update.

Step 2 – Select and download the maps
Visit the website https://garmin.bbbike.org/, choose the Garmin OSM map type, give your map a name, choose the area, provide an email address and select ‘extract’. *

You hopefully will receive an email with a link to a zip file. Download the zip and then extract the files to a temporary folder. You later will be wanting to use the file gmapsupp.img from the compressed file.

* I’ve just updated this section of the instructions in 2022, having originally published my post in 2018. Previously I had used the openstreetmap.nl website to obtain free maps. At the time of writing this openstreetmap.nl redirects to bbbike’s site for people to obtain maps, so I updated the instructions.

I don’t have the Sat Nav anymore to test with, so this part of the instructions are untested by me. Can somebody please kindly leave feedback in the comments below confirming whether this works.

Step 3 – Prepare the SD card and place a map on it
Either place a SD card in the sat nav (when turned off) and connect it to your PC, else use a SD card reader.

The above photo shows a sd card in a reader. The below photo shows a sd card in the 255W.

The next photo shows the sat nav with a usb cable plugged into it.

Create a directory called Garmin on the sd card and then move the gmapsupp.img file to that folder. It is important that the G in Garmin is a capital G.

Note: The 255W sat nav device I used, can’t handle multiple free maps on the SD card and the map file shouldn’t be renamed. I think some later devices might be able to support multiple maps with different names on a SD card.

Note: If you just want to use an SD card, then after completing step 3, proceed to step 6 and ignore steps 4 and 5.

Step 4 – Backup the internal memory and charge the device

Connect the sat nav to a computer via a USB cable and backup the Garmin folder on the internal memory. Then please make sure the sat nav device is fully charged.

Step 5 (optional and dangerous) – Replace a map on the internal memory

Warning: I didn’t run into any problems, but I thought I should warn you that my specific instructions in this step are risky, and could stop you from being able to use the device. At no stage, disconnect or turn the device off during this step! Make sure your sat nav has been charged up before proceeding.

2nd Warning: You should avoid this step if you can!

Please note: If you only want to use add one new map, then you can just use a map via the sd card, and if necessary probably unselect any unwanted maps via the device’s settings.

Extract a gmapsupp.img file from a zip file to a computer (not the sat nav device) you downloaded during step 2, and then rename the file gmapprom.img .

Then delete only the gmapprom.img file in the Garmin folder on the internal memory of the sat nav.

original gmapprom.img file

Now immediately copy your newer (the file you renamed) gmapprom.img file from a computer to the Garmin folder on the sat nav’s internal memory (not SD card).

Sat Nav 255W with new map on internal memory

Step 6 – Eject the device, turn it off, insert the SD card and turn it on!

As I mentioned, these instructions are primarily written for me! So step 6 could be somewhat different for you.

Eject the device if it was connected to the computer and then turn it off. Now turn the sat nav on and hopefully any new maps are available.

Note: You should check that the map(s) you want to use have been recognised and are selected.

1. On the main screen select ‘Tools’.
2. Now select ‘Settings’.
3. Then choose ‘Map’.
4. Finally ‘Map Info’.

Below shows a couple of maps: The top one is on the sd card and the UK map is on the internal memory.

Conclusion

Apart from step six almost giving me a heart attack, the process was easy and I think the device is great. I will probably update the maps again at some stage.

The 255W is an old device and personally, I quite like the look of newer models.

Note: Please don’t leave comments asking for technical support, as I don’t own this device and can only provide limited responses. If helpful, a thank you would be appreciated.