I go by minhag hamakom. In NYC, I bump like a banshee. In most other places, I try not to touch, but am more careful in cities where people are more careful.
One time, there was simply nowhere to park except one very small space, which I wasn’t even sure my car would fit into. I bumped and bumped, and got my car in, with approximately 2-3 inches combined on both sides (I have pictures to prove it, and I am not exaggerating.)
When I came back, the guy in the car behind me was sitting in his car. So he calls me over to yell at me. So he is an old man, so I go over, and listen, and apologize, and say I was very gentle, etc. Then, we start shmoozing, and I end up there shmoozing with him for 2.5 hours. He was an old frum man, whose wife had died, and had fought in Normandy.