i just bought a 98 civic hatchback

runs great and everything but when i take it on the highway, and i'm going 100km/hr it starts to shake, everything shakes, why's that?

 

Could be a number of things from tires to suspension. Does the car bounce more than 3 times if you push down on a fender then release. This would indicate a shock is on its way out. Another thing to check would be to lift the car and push and pull each tire to check for play. If a belt has shifted in the tires you might want to try swapping out with a spare set, if you have them. Also if your in Canada check and see if you have snow tires on, they aren't really good at high speeds. Hope some of this helps.

 

Don't forget the simple things...check your lugnuts, you might be loosin a wheel. OR get your wheels balanced, if you got something out of balance, that usually shows up at highway speeds

 

I'd say its a broken belt of your tires need to be balanced

 

In the winter time, one can sometimes get vibration when snow is stuck in the wheels after a snow storm or after driving through thick snow. Usually what will happen is the vibration will gradually fade away after 10-20 minutes but then you have to remove the excess snow if it doesn't completely go away. But like someone mentionned, it could be a balancing problem, and I've already seen a bad batch of winter tires.

Best regards,
Waldo

 

hmm.. suspension it seems ?..

 

I would get your wheels balanced, and your alignment checked