spare tyre friend
A friend who is primarily used as a backup wen other, more entertaining options go awry or are simply unavailable. The "side dip" of the friendship list. The "Wii" when the other more entertaining friends Xbox and PS3 have been broken through excessive use. The "spare tyre", the one you were hoping not to use.
1. When a friend,lets call him Jack, only starts talking to you at a late hour, lets say 01:25. But at no other time...YOU are the spare tyre friend