I wouldnt say that its because it;s old, my 1981 car does 90MPH (over 130 km/h) smoothly. Bring it to an experienced mechanic. I couldnt tell you whats going on without driving it myself.my guess is though, that you have 2 problems:fuel filter clogged, and the wheels need to be balanced. you said you got new tires and if course i'd assume they balanced them when they put the new tires on, but who knows, maybe they forgot to, or a weight fell off afterwards...Is it fuel injected or carbureted? The Hondas with carburetors had a whole mess of vacuum lines that all have to be properly connected for the car to run right. There is a diagram under the hood, and the lines are all tagged with numbers, go in there, look at the diagram, and check that they're all properly hooked up to where they're supposed to go.if it's fuel injected you could have a dirty injector, or the fuel pump is starting to go bad.also, is you check engine light on??