Towed, Rene and 275 are correct, the GRP roof section would come under a lot of stresses if some sort of bracing is not fitted. If you don't want to fit the supplied "cage" maybe forming a close fitting framework of 25mm steel box section glassed to the inside of the roof linking into windscreen frame, behind door shuts and down the rear pillars to the Z3 boot structure might do the job. This is a MAYBE, I know from production MX250's and the SWB prototype that the cage system works, a smaller section frame may not have the same torsional strength.
Rene is spot on with the curb/string comment, I am currently driving a targa roofed Mk2 MR2 and park on the pavement outside my house overnight, on frosty mornings you can hear the roof panel joints crack as you drive off the curb. The BMW Z3 is very rigid structurally for a convertible but they do still flex.
Last edited by Tribute Automotive; 21st February 2015 at 17:07..
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