How much does suspension and tires have on stopping distance? (looking for a reputable study)

Anyone know of any reputable studies that have tested the effect of shocks/struts and tire wear (tread) on a car's stopping distance? People are always telling me, and at autobody shops they advertise additional distances on the floor and stuff. But I want to know if there are any reputable sources out there that have tested this stuff.Everything i can find are ads from parts manufacturers or dealers, which has me suspecting bullshit.like these two videos (warning: they're ads, sorry...)Video1 Video2ps: i know it's against the rules to post promotional stuff, but that's exactly my point.. i want not promotional stuff. plz n0 ban. via /r/cars http://ift.tt/2uMAi62