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      09-12-2008, 02:19 PM   #35
synclastica_86's Avatar
Hong Kong

Drives: F32 435i, E92 M3, S550
Join Date: Aug 2008
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Originally Posted by KenH View Post
"The M3 sedan is quite a bit taller than the coupe, so a CF roof probably wouldn't quite have the effect as it does on the coupe..."

The sedan is 1.4 inches taller than the coupe so therefore a lighter roof higher up would have more of an effect on the sedan's CoG than on the coupe.
The glued-on CF roof adds torsional rigidity to the bodyshell in comparison to a bodyshell with just the cross strut (and no roof or one not glued on).
This is why manufacturers (starting with FIAT on the 128 in about 1970) glue in the windshields these days. Previously they used to sit in a piece of rubber and "float" which added nothing to the torsional rigidity.
Wait... I don't really get it. Why does gluing on a CF roof help add torsional rigidity? A steel roof doesn't float too, would that give the same strength as gluing a CF roof on?

Current: BMW F32 435iA M-Sports; BMW E92 M3, M-DCT; Mercedes W221 S550 4matic; Ford Fiesta ST; Nissan Silvia S15 Spec-R
Retired: BMW E93 323iA; BMW E85 Z4 3.0i, SMG; Lexus IS 250 AWD; Lexus GX 470; Mercedes W203 C230 Sportscoupe; Peugeot 206 S16; Peugeot 206 RC