CLANDER

Just wondered why Subaru designed the Impreza without window/door frames.

Just for design and looks? or is it better for aerodynamics?

Is a car stiffer with frames? (like the convertible doesn't have a rollcage so is less stiff) Or without frames would that help in allowing the car to flex and be thrown about more?

As you can tell I'm not too technical, but just wondered.

Cheers
CHRIS.
Red '94 WRX with white spot covers

greasemonkey

The underlying reason is that it's just a common styling cue that's carried throughout the Subaru range. Someone at FHI decided one day that Subarus should have frameless doors, so they did. It's no more scientific than that.

There's no inherent structural advantage to building a framed door, no. Don't forget that the door is isolated from the bodyshell by a rubber seal around most of its perimeter, so it's not like it can add much in the way of stiffness.

In most cars the windowframe is there for no reason other than to carry the window seal, so in some ways Subaru's solution is quite elegant in that it eliminates a load of rubber, and hence some weight, but it also make the windows harder to seal effectively, which causes problems with NVH.

That's a far more drastic case than removing the frames on the doors. On an Impreza (and indeed any other modern, monocoque, bonded windscreen car), the design of the doors makes little difference to the overall torsional stiffness. That strength is designed into the shell itself.

The lower half of the doors certainly do have strength designed into them, but that's so they're better at protecting passengers in the event of a side impact.

CLANDER

Cheers greasemonkey!