Re-post of http://forum.xda-developers.com/android/development/guide-root-method-lg-devices-t3049772

1. Get LG Drivers Here: http://www.lg.com/us/support-mobile/lg-D850-Blue-Steel#software
2. Download LG Root
3. Use ADB Shell to copy the files to the temp directory on the phone

   adb.exe push busybox /data/local/t<span id="searchBubble" class="searchBubble"></span>mp/ &amp;&amp; adb.exe push lg_root.sh /data/local/tmp &amp;&amp; adb.exe push UPDATE-SuperSU-v2.46.zip /data/local/tmp

4. Reboot into Download mode
5. Use ports.bat to determine the DIAG port of the phone (Mine was COM 4)
6. Use SendCommand.exe to get a shell within download mode
7. Run the shell command to root the phone from download mode

   sh /data/local/tmp/lg_root.sh dummy 1 /data/local/tmp/UPDATE-SuperSU-v2.46.zip /data/local/tmp/busybox

8. Reboot the phone
9. To allow apps to write to external (http://www.mediamonkey.com/support/index.php?/Knowledgebase/Article/View/163/12/android-sd-card-content-cant-be-addedediteddeleted): Edit /system/etc/permissions/platform.xml

   <permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
           <group gid="sdcard_rw" />
           <group gid="media_rw"  />
       </permission>

10. Reboot the phone