Do BMW frames really crack?


Hello all !! It’s been a while. My last item was getting opinions on what small sports car I should buy. Well other things came up and I had to put this on hold. I am looking again and I have it down to Mazda Miata, BMW Z3, and Corvette. That is the order I like them. I just think the Miata would have a good fun factor and do it for the lowest price on up-keep.
My question… I was afraid to look at BMW because I was told the rear sub-frame cracks and it is about $5000 to repair. I then talked to a BMW tech and he said, yes, they do crack but only about 2% will and only if abused. I have little in the luck department, so that is a concern. So, anyone have any Z3 experience to pass along? Anyone have a frame cracking problem? If I google it, I get a bunch of people telling about this. The BMW techs take is no one who is happy with their car puts it on the internet. Only the few who are Pi@#$$ off because it happened to them.
Any thoughts?

My wife’s aunt, who is older, has owned a Z3 for quite some time and this issue has not manifested itself. I can only speak to her experience, and she just loves the car.

I, too, have heard about it on the internet. The story I read was a guy that loved his Z3. He was getting an alignment after putting new tires put on, and the alignment tech noticed the cracks in the unibody at the rear sub-frame. Apparently, the reinforcing of the unibody to the rear subframe is not strong enough, and stress cracks begin to form. The fix was welding in extra plates to reinforce the body mounts. It is common with those that drive their cars hard or modify them for racing, but it has happened to others that just drive them normally a bit more rarely.

I’ve heard of this problem but am not familiar enough with the cars to know how much of a problem it has been with them.
Some neighbors of mine bought a brand new Z3 some years back when they first came out, still have it to this day, and have had zero problems with it.

My feeling is that if the frame is fine now with no cracks and no rust then it should be fine for the duration unless beaten into the pavement.
I think what causes this problem is the beginning of a tiny stress crack that goes unnoticed and spreads all over, especially if the car is driven aggressively. This is why all cars on occasion should have the chassis and suspension inspected.

That being said, I think the Miata would be a better choice. Z3 repair parts will generally not be cheap anyway even if you exclude the frame thing.

The Z-3 frame cracks occur where the rear differential is bolted to the unibody sub-frame…The harder you drive the car, the more likely the problem…

When you find a Z3 you like, have the frame inspected along with the rest of the car. If the frame looks OK, the consider it. Unless, of course, you plan to drive it in a manner that would lead to cracking the frame.

Thanks to all. Problem solved, I bought a Miata. I will now start another discussion. I haven’t did much to cars in a while. I am actually gettting a little excited to start working on it. It does need some work, and I don’t know much about Mazda.
Thanks again for the help