Car shakes when the sunroof is off

[Natty]

I have an S13 fastback with the glass flip up sunroof (or moonroof?) that can be removed and stowed in the trunk. I drove with it off for the first time and the car begins to shake a bit at about 15-35mph. I never went above 60mph, but it does appear to happen only from 15-35mph.
I guess the wind gets in and hits the back of inside of my headliner/roof/hatch and priduces a bit of lift/resonance?

How can I stop it? I am sure this is not normal, as Nissan put the feature on the car, so I am sure it is meant to work.

Jeff

[twitchy]

okay, see if you have 2 little plastic flaps where the roof and glass meet, like in the lip, on either side, towards the front of the car and flip them up when your going to get that resonance, in city driving, about 60 to 80 kms

You were right about WHY it does that, its air pressure, same kind of thing on an airplane wing.

if you dont have the flaps or they dont work for some reason, crack a window more than a half inch and it will even pressure out

good luck