smoiking tire tests an armord merc

It would depend on what level car it was. Most up-armored cars should be able to shrug off 9mm with no issues as long as the rounds were spread out a bit. You can get some degradation in the glass if the rounds are all impacting a small area. For instance, 7.62x39 will eat through a level 7 car's window in 5-8 rounds if they are all hitting in the same place. Eye pro is a must because even if the bullet is stopped, the laminated sheets can still fracture all the way to the innermost sheet and you can get some pieces flying off the window into the interior of the car. 5 or 6 rounds of 9mm spread all over the car? No worries.

I would (and have) let someone shoot at me with non-AP rounds in a level 4 or 7 to avoid cracking the seal on the armor. It's when they're shooting at you with a DshK or a PKM that you either need to drive the hell out of there or get out and kill them.

The up-armored Mercs weren't worth a shit in Iraq because the suspension wasn't built to be driven over bad roads (much less at high speed), if the tires were shot out they were slower to change (a shredded run-flat dropped the car real low. Too low for the floor jacks we carried in the Subs.) and they didn't have the acceleration that the beefier vehicles had. The only advantage that they offered was a lower profile than a Suburban, Land Cruiser or G-wagon. They could be used for single car advances (no 100M standoff, just dark window tint and curtains in the back) and attract far less attention than a couple of SUVs.