GM-GMC: hit from behind, spare tire carrier, rear brakes

Question
When is stop completely at lights, or a stop sign, i sometimes fell a slight 'hit from behind'... its like a car tapped my car from behind but it isnt... is this the brakes? do i need new brake pads or is it worse?

thnx

Answer
in response to your question......you did not mention what kind of vehicle you drive, it sounds to me like something is loose in your truck/car/van perhaps something in the trunk or a spare tire carrier under the vehicle? It could be pausible that the rear brakes are very miss-adjusted or there could be a propotioning valve problem causing the rears to apply after the fronts.....I would check the most obvious first. Hope this helps!