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Ex-Dictator
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Discussion Starter · #1 ·
Does the sunroof have a negative/positive effect on the body rigidity ?

I found the rigidity figures, but they are only with/without fold down rear seats.

Thanks
 

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.
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On the Honda's I've owned in the past, it has somewhat. Probably somewhat less noticeable in the BMW because the structure is so stiff. Nonetheless, having a hole in the roof will decrease the rigidity slightly if no extra "stabilizing support" is put into place.
 

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Usaully, the sunroof only effects rigidity when it is added as an aftermarket product. Some installers are real hack artists, and can destroy the rigidity of the crossmembers. I saw one installer cut about 3" out of a crossmember in a Chyrsler Lazer, and all he had to say was "opps"


FF might be right about japan cars, I am almost 6'5" tall, and can not fit in anything made in japan:D But I think most manufacture's make considerations in weldments when they know a sunroof is to be installed in the production line.
 

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Hmm...I dropped the moon-roof and fold-down seats options from my 325i when I ordered it. I regretted 2 days after and wanted the moon-roof, cos afterall, this is California and I had a moon-roof on my VW.

Turns out that I can live without moon-roof anyway. :D

And yes, it will affect the rigidity. Whenever you have stamped out a piece from a solid plate, the remaining plate is not as rigid. But of course if you like driving under the sun, why not? :D
 

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zeddy
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Alex Baumann said:
Does the sunroof have a negative/positive effect on the body rigidity ?

I found the rigidity figures, but they are only with/without fold down rear seats.

Thanks
Rigidity is affected ONLY when the roof is open. Otherwise the body's solid as a rock (or the same as the non-sunroofed model).

Same with opening the windows. All windows down = less rigidity. Roll 'em back up and you've got a solid enclosure once again.

Ed
 

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King of Rear Clunks
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I debated this when I was spec'ing out my car. Sunroof probably does affect body rigidity (open or not, since the glass rides in rails and has a soft seal, and thus is not structural), but in something as stiff as a E46, not to any noticeably degree. OTOH, separate torsional rigidity figures are given for sedans with and without folding seats, and the associated steel panel that goes with that. The other things to consider are headroom and center of gravity, as it does add a little weight at the top of the car.

BMW does claim in MINI literature that the hugeass sunroof on that thing doesn't affect rigidity at all...
 

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Not sure about the overall effect of the sunroof. While I agree that if you cut a hole out of a solid piece the rigidity would go down, I am not sure that they "just cut a hole" in the roof. Remember in the stamping process, that the hole is cut and then the edges are folded .... so instead of having a flat surface you get something that looks like a half an I-beam. So instead of a flat piece with a hole you now have a 3D-structure that should have increased rigidity.
 

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M Mad
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Interesting article in Total BMW about a racing 5 series. They used a sunroof body, because BMW puts in extra structure to reduce the loss of rigidity. But inthis case with the race car they welded the sunroof shut so got the rigidity of no sunroof, with the extra structure of sunroof car.
 
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