Quote:
Originally Posted by Smallblock454
The problem here is that the windscreen glass and the windscreen frame as constructive element add the rigidity. If you remove the glass you loose a lot of rigidity. You'll get the the best rigidity with windscreen frame, windscreen glass and sidewindows up. Without windscreen glass you'll get a lot more torsion in the front.
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i'll disagree with that. regarding rigidity of the boxster chassis, you have two concerns - (a) rigidity of the front subframe, and (b) rigidity of the front subframe relative to the rear subframe.
in the front sub-frame, the only opportunity for relative movement of the various components is at the strut top mounts. specifically, they may try to spread apart when subject to cornering loads. this is where a strut brace comes into play - it stops that from happening (which is why they can be made of carbon fiber - they don't need to deal with compression, only tension). they may also try to move a bit forward/backward if subject to caster loads, but note that there are already triangulation braces in the car. to support those braces i would also note the quality of steel used in that area as per the following:
regarding relative motion of the front and rear subframes (typically a torsion or twisting force - that creaking you get when you drive over a driveway lip unevenly for example) is not going to be impacted by your windshield or the presence of any strengthening along the upper forward cowl. to address this, look to reinforcing that big flat open space between the front and rear wheels - which is why you keep your door structure in place unless adding a cage.
rollover protection, front impact protection? yeah, keep your windshield. and your airbags. and your factory seats. and seatbelts. not certain that's what this is about, however. do check your regs; the broomstick test looks different without a windshield - oem rollbar probably not high enough.