I just got a new SIGLA brand windscreen installed and the fit wasnt perfect but we thought it would work. After a few hours of mounting it into place the right hand lower corner had sprung up about 1/4" and stretched the bytul rubber a bit. I pushed it down again and got it to stay reasonably in place. The next morning I had a nice crack from top to bottom on the righthandside of the windscreen and the corner had sprung back up again.

The fit is ok all around but it seems the lower corners just arent curved enough to fit the car? Has anyone else experienced the same?

(I did use the rubber spacers along the lower edge of the screen.)

That sucks!!!!!!
And not just for you, what does it mean for those who intend to use an
"original" part on their "faithful" restoration.
Pay for a premium part then find out that it's inferior ? or defective ?
Is there any chance your car has damage at or near the windshield frame ?

That would be my guess as well. If they made one defective windscreen then they made a thousand that way. FWIW, it helps to do this in the sun or a very warm room. The width of the butyl tape tells the story.

I had the same problem, but with a brand new OEM-spec windshield from Pilkington. I paid $250 for the windshield, which was in a special batch of 40 that had been recently produced, but when I went to mount it on my car, the bottom edge curve was too shallow, and resulted in the lower corners being about 3/8" from the window frame/body. The rest of the windshield fit perfectly and was the right dimensions. My car had no frame damage or warping to speak of.

Happily, Pilkington was willing to take it back and provide a refund. While I was at their distribution warehouse, they even let me measure the other windshields to see if any would fit. Not a single one (of the 12 I measured then, fit). What's more, they said someone else had returned theirs with the same complaint.

I'd written this off as a bad batch, but the fact that you've had the same problem makes me wonder if there was some discrepancy in that lower curve radius on some of the cars.

Interesting that I'm not the only one with this experience.
I could live with the crack the problem is that it wont pass the annual checkup with a cracked windscreen, its an automatic fail that needs to be fixed within 30 days or the car is illegal to drive... :/

Were all the poor fitting windshields marked Sigla/Pilkington ?

That's why I paid to have mine installed. Not my problem at that point. I understand the OEM butyl rubber, but you can't tell the difference until you go to remove it and If it comes to that I'll be paying my body guy. I will get a good eyeball on it before I have it reinstalled. And if it need some work it will get done.

I believe having a glass installer is the safest way to have it done. They break it, they replace it. I could never accept a crack in a new windshield.

Yeah when I replace this one it will be at the autoglass shop. It just wasnt an option now as the car isnt driveable yet.