There's a distinct vibration going through my car when I drive. I don't feel it at idle, even if I rev up or something. If I had to try to judge where it's coming from just from what little I know mechanically and by reason, I'd say it's coming from one wheel. At low (city-driving) speeds I generally don't notice it at all, and it seems like once I get up to interstate speeds, say 70 mph or more, I really don't notice it either. It's by far its worst around 55 mph.

Relevant facts about the car itself:
2000 Civic EX coupe
5-speed
Eibach Sportlines
Monroe Sensa-Tracs
15" Konig Heliums
Kumho rubber

My first inclination is just to take it somewhere and have the tires rotated and balanced. To me, it feels like a wheel is out of balance, but the only thing I can't figure out is why I'd notice that at 55 mph but not 75. To me, that would rule out a tire being low. Also, none of them LOOK low. There's not a particularly loud sound that accompanies the vibration, though there may be a slight whump whump whump. I really can't pin that down, and wouldn't want to commit to it.

What do you guys think?

 

get your tires balanced, its the cause 90% of the time

btw, you are in the 88-91 forum

 

does it happen to occur after very slight steering inputs?

and why are you posting this in the crxforum?