It will remain unnoticed until you have a bad wreck, then it becomes a very painful hockey puck bouncing around your head. Don't forget your color coded hair bonnet off of the tire. Remember, there is a reason that they don't put loose heavy objects in the cabin with the occupants. Here in town we just had a guy bounce a large stereo speaker off of his head when he hit a tree, he wasn't impressed with the results when he finally woke up. A word of caution!