Any fool who tried to ram that vehicle with an ordinary street car would be in a world of hurt from the impact, let alone the SS. The presidential limo is built like a small tank underneath its pretty skin. It weighs about 7 tons with armor plating estimated to be 8 inches thick. And it has gigantic Goodyear tires reinforced with Kevlar run-flats. It's designed to stay intact and keep running under severe attack. In contrast, the average street car/SUV weighs in the range of 2 tons, some a little less, some a little more, and are designed to absorb impacts by crumpling. No contest.
While I do not doubt that it is very well armored, I strongly doubt it is 8’’ of armor plate. You’d exceed your 7 tons figure in not many square feet. You’re talking thicker armor than a WWII heavy cruiser, at 8” (!!).